System, device, and method for establishing wireless link

Abstract

To provide systems, devices, and methods for establishing a wireless link such as for exchanging wireless power, data, or signals through tissue.SOLUTION: In a wireless system, a first device 210 generates wireless signals. A second device 214 comprises a processor, and one or more arrays 220 of transducer elements 222 which receive the wireless signals from the first device implanted in the heart surrounded by tissue 270 and ribs 272. The processor generates first device data based on the received wireless signals. The transducer arrays 220 exchange one or more of the wireless signals with the first device based on the first device data.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 62 / 872,256, filed July 10, 2019, U.S. Provisional Patent Application No. 62 / 929,684, filed November 1, 2019, and U.S. Provisional Patent Application No. 63 / 036,298, filed June 8, 2020, each of which is incorporated by reference in its entirety.

[0002] The devices, systems, and methods herein relate to exchanging one or more of wireless power and wireless data between wireless devices, such as an external wireless device and an internal device located within a patient. [Background technology]

[0003] Devices such as physiological sensors and stimulators (e.g., pacemakers) can be placed inside a patient's body and configured to monitor, diagnose, and treat the patient. These conventional devices can form a wireless power and / or data link with another device placed outside the body. However, establishing and maintaining a robust and reliable link between an external device and an internal device can be difficult due to interference from tissues within the body and movement of the internal device during use. For example, a patient's breathing, movement, and cardiac activity can change the location and / or orientation of the internal device within the body, reducing the efficiency of the wireless link between the internal and external devices. Therefore, additional devices, systems, and methods for establishing a wireless link may be desirable. Summary of the Invention

[0004]

[0003] Described herein are systems, devices, and methods for establishing a wireless link, such as exchanging power or data through tissue. Generally, the system can be configured to establish a closed-loop link for exchanging one or more of wireless power and wireless data. In some variations, the system can include a first device (e.g., an implantable medical device) configured to generate a wireless signal, and a second device (e.g., an external wireless device) including a first transducer array, a second transducer array, and a processor, where the first transducer array can be configured to receive the wireless signal from the first device, the processor can be configured to generate first device data based on the received wireless signal, and the second transducer array can be configured to exchange one or more of wireless power and wireless data with the first device based on the first device data.

[0005] In some variations, the first device can comprise an implantable medical device, and the second device can be configured to be placed external to the patient's body. In some variations, the first transducer array and the second transducer array can each comprise an ultrasound transducer array. In some variations, the second transducer array can comprise a one-dimensional linear array or a two-dimensional array. In some variations, the first transducer array can comprise at least three non-collinear transducer elements.

[0006] In some variations, the first transducer array and the second transducer array may include separate transducer elements. In some variations, the first transducer array and the second transducer array may include at least one identical transducer element. In some variations, the first transducer array may include a subset of the second transducer array. In some variations, the second device may include a third transducer array configured to transmit an interrogation signal to the first device, and the wireless signal may include a feedback signal generated in response to the interrogation signal. In some variations, the third transducer array may include transducer elements separate from each of the first transducer array and the second transducer array. In some variations, one or more transducer elements of the second transducer array may be configured to receive a wireless signal from the first device. In some variations, the wireless signal may include wireless data.

[0007] In some variations, the one or more transducer elements of the first transducer array and the second transducer array can be interleaved or interspersed. In some variations, the second transducer array can be configured to exchange one or more of wireless power and wireless data with the first device based at least in part on one or more of interpolation and extrapolation of the wireless signals.

[0008] Also described is a system configured to establish a closed-loop link for exchanging one or more of wireless power and wireless data. In some variations, the system can include a first device, a processor, and a second device comprising a transducer array including a plurality of subarrays, where the first subarray can be configured to transmit an interrogation signal to the first device, the second subarray can be configured to receive a feedback signal from the first device, and the processor can be configured to cycle through one or more of the plurality of subarrays until the received feedback signal satisfies a predetermined condition.

[0009] In some variations, the first device can include an implantable medical device, and the second device can be configured to be positioned external to the patient's body. In some variations, the transducer array can include an ultrasound transducer array. In some variations, the subarray can include one or more transducer elements of the transducer array. In some variations, the first subarray and the second subarray can include the same transducer elements. In some variations, the predetermined condition can include a strength of a received feedback signal calculated for one or more transducer elements of the second subarray. In some variations, the processor can be configured to select a transducer configuration based on the received feedback signal that can satisfy the predetermined condition, the transducer configuration being configured to exchange one or more of wireless power and wireless data with the first device. In some variations, the transducer configuration can include one or more transducer elements of the transducer array.

[0010] Also described are systems configured to establish a closed-loop link for exchanging one or more of wireless power and wireless data. In some variations, the system can include a first device, a processor, and a second device comprising a transducer array including a plurality of subarrays, where the first subarray can be configured to transmit an interrogation signal to the first device, the second subarray can be configured to receive a feedback signal from the first device, the feedback signal including one or more of digital first device energy data and digital interrogation signal strength data, the processor can be configured to select a transducer configuration based on the feedback signal, and the transducer configuration is configured to exchange one or more of wireless power and wireless data with the first device.

[0011] In some variations, the first device can include an implantable medical device, and the second device can be configured to be placed external to the patient's body. In some variations, the transducer array can include an ultrasound transducer array. In some variations, the subarray can include one or more transducer elements of the transducer array. In some variations, the first subarray and the second subarray can include the same transducer elements. In some variations, the transducer arrangement can include one or more transducer elements of the transducer array. In some variations, the first device can include a power source including one or more of a rechargeable battery, a capacitor, a supercapacitor, and a non-rechargeable battery. In some variations, the digital first device energy data can include power source parameters including one or more of a voltage, an energy level, a charging voltage, and a charging current. In some variations, the transducer arrangement can be configured to wirelessly recharge the power source.

[0012] In some variations, the interrogation signal may include a first frequency, and one or more of the wireless power and the wireless data may include a second frequency different from the first frequency. In some variations, the first device may include at least one ultrasonic transducer including a first impedance corresponding to the first frequency and a second impedance corresponding to the second frequency, where the first impedance is greater than the second impedance. In some variations, the first device may include a first ultrasonic transducer including a first impedance corresponding to the first frequency and a second ultrasonic transducer including a second impedance corresponding to the second frequency, where the first impedance is greater than the second impedance.

[0013] In some variations, the interrogation signal may include a wide ultrasonic beam. In some variations, the first device may include an ultrasonic transducer, and a diameter of the wide ultrasonic beam upon emission from the first device may include a diameter greater than a dimension of the ultrasonic transducer. In some variations, the interrogation signal may include one or more of an identifier, a code, and a command. In some variations, the interrogation signal may include a radio frequency (RF) signal.

[0014] In some variations, the feedback signal may include one or more analog pulses. In some variations, the feedback signal may include one or more of an analog pulse, an acknowledgment signal, a digital energy state of the first device, a digital interrogation signal strength, an identification number, a code, a command, and one or more parameters of the first device, the wireless power signal, and the data signal. In some variations, the feedback signal may include one or more ultrasonic reflected signals corresponding to the interrogation signal. In some variations, the feedback signal may include one or more ultrasonic backscatter signals corresponding to the interrogation signal. In some variations, the first device may be configured to modulate the ultrasonic backscatter signals. In some variations, the first device may be configured to transmit the feedback signal at one or more frequencies. In some variations, the processor may be configured to identify a frequency of a transducer arrangement for transmitting one or more of wireless power and downlink data to the first device based on the feedback signal. In some variations, the identified frequency of the transducer arrangement may correspond to a frequency of the feedback signal at a maximum amplitude. In some variations, the feedback signal may include periodic transmission of one or more of an analog feedback signal and a digital feedback signal.

[0015] In some variations, the transducer arrangement can include one or more transducer elements configured to focus one or more of wireless power and wireless data to the first device. In some variations, the transducer arrangement can include one or more transducer elements configured to beamform signals. In some variations, the transducer arrangement can be configured to disable a set of transducer elements of the transducer array based on the strength of a received feedback signal.

[0016] In some variations, the transducer configuration can be selected based on one or more of time reversal, triangulation, and intensity estimation of the feedback signal. In some variations, the transducer configuration can be selected based on one or more of time reversal, triangulation, and intensity estimation of one or more analog pulses. In some variations, the processor can be configured to adjust one or more of the transmit power and transmit duration of the transducer configuration based on the feedback signal. In some variations, the processor can be configured to monitor one or more of the time-averaged output power of the second device, the peak output power of the second device, heating of one or more of the second device and the skin, heating of the first device, heating of the tissue structure, acoustic intensity in the tissue, and energy level of the second device. In some variations, the first device can be configured to monitor one or more of the heating of the first device and acoustic intensity incident on the first device. In some variations, the processor can be configured to adjust one or more of the transmit power and transmit duration of the transducer arrangement based on one or more of the time-averaged output power of the second device, the peak output power of the second device, heating of one or more of the second device and the skin, heating of the first device, heating of the tissue structure, acoustic intensity in the tissue, and energy level of the second device. In some variations, the processor can be configured to locate the first device and adjust one or more of the transmit power and transmit duration of the transducer arrangement based on the feedback signal. In some variations, the processor can be configured to locate the first device based on one or more analog pulses and adjust one or more of the transmit power and transmit duration of the transducer arrangement based on one or more of the digital first device energy data and the digital interrogation signal strength data.

[0017] Also described are methods for establishing a closed-loop link for exchanging one or more wireless signals. In some variations, the method can include transmitting an interrogation signal to a first device using a first sub-array of the second device, receiving a feedback signal from the first device using a second sub-array of the second device, selecting one or more transducer configurations of the second device based on the feedback signal, and exchanging one or more wireless signals with the first device using the one or more transducer configurations of the second device during a plurality of intervals, where the wireless signals include one or more of a power signal, a data signal, an interrogation signal, a feedback signal, a downlink signal, and an uplink signal.

[0018] In some variations, the method may further include transmitting a feedback signal from the first device in response to one or more wireless signals received by the first device during one or more of the intervals. In some variations, the method may further include detecting one or more of: a falling edge of the one or more wireless signals; and a code corresponding to the one or more wireless signals received by the first device.

[0019] In some variations, selecting one or more transducer configurations of the second device may include one or more of determining one or more of a frequency, delay, phase, amplitude, and gain of the selected one or more transducer elements based at least in part on one or more of a delay, phase, time of arrival, time of flight, amplitude, frequency, and encoded data of the feedback signal.

[0020] In some variations, the method may further include determining, in response to the received feedback signal, to transmit one or more of a power signal, an interrogation signal, a data signal, and a downlink signal to the first device. In some variations, the method may further include determining, in response to the received feedback signal, to refrain from transmitting wireless signals to the first device. In some variations, the transducer configuration corresponding to the subsequent interval may be selected based on one or more previously received feedback signals during one or more previous intervals. In some variations, the duration of at least one interval of the plurality of intervals may be determined by the first device. In some variations, the duration of at least one interval of the plurality of intervals may be determined by the second device. In some variations, the first device may be configured to periodically transmit a feedback signal during one or more of the intervals.

[0021] In some variations, the one or more transducer configurations can be selected based on time reversal. In some variations, the method can further include identifying a frequency of the feedback signal, and the one or more transducer configurations can include the identified frequency. In some variations, the method can further include identifying a frequency of the feedback signal, and the one or more transducer configurations can include a frequency different from the identified frequency.

[0022] In some variations, selecting one or more transducer configurations of the second device may include estimating a set of spatial coordinates of the first device using triangulation, and exchanging one or more of wireless power signals and data signals using the one or more transducer configurations may be based at least in part on the estimated spatial coordinates.

[0023] In some variations, selecting one or more of the transducer configurations of the second device may include estimating a strength of a feedback signal received by a second sub-array of the second device, and exchanging one or more of wireless power signals and data signals using the one or more transducer configurations based on the estimated strength of the received feedback signal.

[0024] In some variations, the feedback signal may include a digital amplitude of the interrogation signal received by the first device, and selecting one or more transducer configurations of the second device may include selecting one or more of the sub-arrays corresponding to a maximum digital amplitude of the interrogation signal.

[0025] In some variations, the feedback signal may include a first feedback signal, and the method may further include powering the first device by transmitting the first power signal during a first power interval and receiving a second feedback signal from the first device after the first power interval. In some variations, the method may further include intermittently powering the first device, and the second device may be configured to inhibit powering of the first device based on the feedback signal. In some variations, the interrogation signal may be a first interrogation signal, and the method may further include transmitting a second interrogation signal to the first device after a time delay. In some variations, the first device may be configured to transmit the feedback signal after a time delay.

[0026] In some variations, the method may further include selecting a transducer configuration based on a location of the first device. In some variations, the method may further include storing a transducer configuration corresponding to the location of the first device in a memory of the second device. In some variations, the method may further include selecting a stored transducer configuration for exchanging one or more of wireless power signals and data signals with the first device.

[0027] In some variations, the duration of the interval can be predetermined. In some variations, the first device can be configured to transmit a plurality of feedback signals upon receiving the interrogation signal. In some variations, the plurality of feedback signals can comprise pulses periodically transmitted by the first device. In some variations, the method can further include estimating a spatial path of the first device based on the plurality of feedback signals. In some variations, the method can further include selecting a transducer configuration corresponding to the spatial path of the first device based on the estimated spatial path.

[0028] In some variations, the method may further include generating a location notification corresponding to the spatial adjustment of the second device. In some variations, generating the location notification may be based on an estimated spatial path of the first device. In some variations, the spatial adjustment may include aligning an axis of the second device with the spatial path of the first device. In some variations, the second device may include a one-dimensional linear ultrasound transducer array, and the spatial adjustment may include aligning one or more of an aperture and an elevation angle of the array with the spatial path of the first device. In some variations, the location notification may be based on a position of the transducer configuration relative to one or more of a center, an edge, and a predetermined location of the second device. In some variations, generating the location notification may be based on a feedback signal. In some variations, the method may include generating a power notification including a power state of one or more of the first device and the second device. In some variations, the method may include generating a communication notification corresponding to one or more of data received from the first device, physiological parameter data, and parameter data of one or more of the first device and the second device.

[0029] Also described are systems configured to exchange one or more of wireless power and wireless data. In some variations, the system can include a first device including a plurality of transducers configured to receive a downlink signal, and a second device configured to transmit the downlink signal, where one or more of the plurality of transducers can be configured to exchange one or more of wireless power and wireless data with the second device based on the received downlink signal.

[0030] In some variations, the first device may include an implantable medical device, and the second device may be configured to be positioned external to the patient's body. In some variations, the multiple transducers may include multiple ultrasound transducers. In some variations, the system may further include a power circuit configured to DC-couple the received power. In some variations, the downlink signal may include one or more of an interrogation signal, a power signal, and downlink data. In some variations, one or more of the multiple transducers of the first device may be configured to exchange wireless data with the second device at a first frequency that is different from a second frequency of the received wireless power.

[0031] In some variations, the first device may further include a processor. In some variations, the processor may be configured to select one or more of the plurality of transducers configured to exchange one or more of wireless power and wireless data with the second device based on the received downlink signal. In some variations, the processor may be configured to periodically update the selection based on the one or more of the received downlink signals. In some variations, the processor may be configured to calculate a received signal strength of the downlink signal for one or more of the plurality of transducers and compare the received signal strengths of the one or more of the plurality of transducers with each other. In some variations, the processor may be configured to select one or more of the plurality of transducers corresponding to a received signal strength above a predetermined threshold for exchanging one or more of wireless power and wireless data with the second device. In some variations, the processor may be configured to select one transducer corresponding to a maximum received signal strength for transmitting an uplink signal to the second device. In some variations, the processor may be configured to decode one or more downlink commands based on the downlink signal. In some variations, the processor may be configured to select one or more transducers for exchanging one or more of wireless power and wireless data with the second device based on decoding of one or more of the downlink commands.

[0032] Also described are systems configured to exchange one or more of wireless power and wireless data. In some variations, the system may include a first device configured to transmit an interrogation signal through a transmission medium, the interrogation signal in the transmission medium configured to generate a reflected interrogation signal, and a second device configured to receive the interrogation signal from the first device and transmit a feedback signal including at least one parameter different from the reflected interrogation signal.

[0033] In some variations, the first device can be configured to be positioned external to the patient's body, and the second device can include an implantable medical device. In some variations, the at least one parameter can include one or more of amplitude, signal strength, phase, frequency, time delay, and signal modulation. In some variations, the second device can be configured to transmit the feedback signal using one or more of active signal transmission and backscatter modulation. In some variations, the at least one parameter can include a time delay, and the second device can be configured to receive the interrogation signal and transmit the feedback signal after the time delay. In some variations, the time delay can be at least about 10 microseconds. In some variations, the interrogation signal can include a first modulation, and the feedback signal can include a second modulation different from the first modulation. In some variations, the interrogation signal can include an ultrasound signal, and the feedback signal can include a radio frequency signal. In some variations, the interrogation signal can include a radio frequency signal, and the feedback signal can include an ultrasound signal. In some variations, the feedback signal can include one or more of a code and a waveform characteristic different from one or more of the reflected interrogation signals.

[0034] Also described is a method for positioning the wireless device on the body. In some variations, the method can include generating a user prompt corresponding to a desired location on the body and orienting the wireless device according to one or more of an orientation feature and an orientation signal of the wireless device.

[0035] In some variations, providing a user prompt may include one or more of a body location image, a visual indication, and an audio indication. In some variations, the orientation feature of the wireless device may include one or more of a marking, a structure, and a shape of the wireless device. In some variations, the orientation signal of the wireless device may include a signal from one or more of a direction sensor, an accelerometer, a gyroscope, and a position sensor.

[0036] In some variations, the method may include measuring one or more parameters of the wireless device and the body, estimating a position of the wireless device on the body based on the measured parameters, and generating a user prompt corresponding to the estimated position of the wireless device on the body.

[0037] In some variations, the parameters may include one or more of heart sounds, lung sounds, breath sounds, an incoming wireless signal from the implanted medical device, and a wireless reflected signal. In some variations, the user prompt may include one or more of a notification regarding an estimated location of the wireless device on the body and a recommendation including one or more of repositioning the wireless device on the body and contacting a medical professional. In some variations, repositioning the wireless device on the body may include one or more of moving, adjusting, and rotating the wireless device.

[0038] Also described is a method for coupling an ultrasound device to a patient's body. In some variations, the method can include measuring one or more parameters of the ultrasound device and the body, estimating a coupling status between the ultrasound device and the body based on the measured parameters, and generating a user prompt corresponding to the coupling status between the ultrasound device and the body.

[0039] In some variations, the ultrasound device can include one or more ultrasound transducers, and the parameters can include one or more of an ultrasound transducer's electrical impedance, an ultrasound transducer's reflection coefficient, heart sounds, lung sounds, an ultrasound signal transmitted from the implantable medical device, an ultrasound reflection signal, pressure, force, contact, capacitance, tissue's electrical impedance, heat, and temperature.

[0040] In some variations, estimating the coupling status can include estimating one or more of the adequacy and degree of coupling between the ultrasound device and the body. In some variations, the user prompts can include one or more of the coupling status and a recommendation including one or more of repositioning the ultrasound device relative to the body, applying an ultrasound coupling agent, adjusting fasteners of the ultrasound device relative to the body, and contacting a medical professional.

[0041] In some variations, the method can further include periodically transmitting uplink signals from the implantable medical device, and estimating the coupling state can be based on measuring the strength of one or more of the uplink signals received by the ultrasound device. In some variations, the method can further include transmitting an interrogation signal from the ultrasound device and receiving one or more feedback signals from the implantable medical device, and estimating the coupling state can be based on measuring the strength of one or more of the feedback signals received by the ultrasound device.

[0042] Also described are methods for reducing noise to separate an ultrasonic signal from a pressure signal. In some variations, the method may include measuring parameters of the ultrasonic signal received by one or more of an ultrasonic transducer, a pressure transducer, a flow sensor, a force sensor, and a MEMS device, and generating pressure data based on the measured parameters of the pressure signal and the ultrasonic signal measured by the force transducer.

[0043] In some variations, generating the pressure data can include separating the ultrasound signal from the pressure signal. In some variations, separating the ultrasound signal from the pressure signal can include one or more of averaging, digital signal processing, and analog signal processing. In some variations, generating the pressure data can include identifying one or more pressure samples of the pressure data that include measured parameters of the ultrasound signal, and rejecting or flagging the identified one or more pressure samples.

[0044] In some variations, the method can further include measuring the pressure signal using the pressure transducer after a time delay. In some variations, the time delay can be predetermined. In some variations, the time delay can be determined based on dissipation of the ultrasound signal.

[0045] In some variations, generating the pressure data can be performed by a processor of a first device comprising an ultrasound transducer and a pressure transducer. In some variations, generating the pressure data can be performed by a processor of a second device in wireless communication with the first device comprising an ultrasound transducer and a pressure transducer.

[0046] Also described are methods for reducing noise to separate an ultrasonic signal from a pressure signal. In some variations, the method can include receiving an ultrasonic signal using a pressure transducer of the device and filtering the ultrasonic signal using a filter coupled to the pressure transducer. In some variations, filtering the ultrasonic signal can include one or more of analog filtering, digital filtering, analog post-processing, digital post-processing, and the use of one or more of an amplifier, a processor, an integrator, an averager, and a boxcar sampler.

[0047] Also described are methods for estimating heart rate. In some variations, the method may include measuring blood pressure samples using a first device, generating blood pressure data using the measured blood pressure samples, and estimating the heart rate over one or more cardiac cycles using the blood pressure data.

[0048] In some variations, estimating the heart rate can be performed by a processor of the first device. In some variations, estimating the heart rate can be performed by a processor of a second device, the second device being in wireless communication with the first device. In some variations, estimating the heart rate can include comparing one or more of the blood pressure samples to a predetermined threshold, identifying two or more crossing points at which the blood pressure samples may cross the predetermined threshold, and estimating the heart rate based on one or more elapsed times between the identified crossing points.

[0049] In some variations, estimating the heart rate can include identifying local maxima or minima in the blood pressure samples and estimating the heart rate based on one or more elapsed times between two or more local maxima or minima. In some variations, estimating the heart rate can include identifying maximum or minimum rate-of-change points in the blood pressure samples and estimating the heart rate based on one or more elapsed times between two or more maximum or minimum rate-of-change points. In some variations, estimating the heart rate can be based on a frequency domain representation of the blood pressure samples.

[0050] Also described are systems configured to exchange one or more of wireless power and wireless data. In some variations, the system can include a first device configured to traverse a spatial path within a patient and a second device configured to exchange wireless signals with the first device only during an access period.

[0051] In some variations, the first device or the second device may include a sensor configured to measure one or more physiological parameters of the patient and a processor configured to identify an access period based on the measured one or more physiological parameters. In some variations, the one or more physiological parameters may include one or more of blood pressure, heart rate, respiratory rate, heart sounds, lung sounds, and an ECG.

[0052] Also described are methods of parameter tracking. In some variations, the method may include tracking one or more parameters corresponding to a wireless system comprising a first device and a second device, selecting a transducer configuration for the second device based at least in part on the parameters, and exchanging one or more wireless signals with the first device using the selected transducer configuration.

[0053] In some variations, the parameters may include one or more of a wireless link gain between the first device and the second device, a transmit power of the second device, a transmit frequency of the second device, one or more parameters of a transducer configuration, one or more parameters of the first device, an energy state of the first device, a battery life of the first device, a parameter corresponding to a sensor of the first device, a parameter corresponding to a transducer of the first device, a transmit frequency of the first device, a transmit power of the first device, one or more positions of the first device, one or more orientations of the first device, and a physiological parameter of the body. [Brief explanation of the drawings]

[0054] [Figure 1] 1 is a schematic block diagram of an exemplary variation of a wireless system. [Figure 2] 1 is an exemplary cross-sectional schematic diagram of a variation of a wireless system. [Figure 3A] 10A-10C are exemplary cross-sectional schematic diagrams of variations of wireless systems comprising subarrays configured to transmit interrogation signals. [Figure 3B]10 is an exemplary cross-sectional schematic diagram of a variation of a wireless system including a feedback signal generated from a first device. [Figure 3C] 10A-10C are exemplary cross-sectional schematic diagrams of variations of wireless systems including a transducer arrangement configured to transmit wireless power to a first device. [Figure 4] 1 is an exemplary cross-sectional schematic diagram of a single ultrasound transducer and an ultrasound beam in tissue. [Figure 5] FIG. 1 is a schematic block diagram of an exemplary variation of a first device, such as an IMD. [Figure 6] 10 is a flowchart of an exemplary variation of a method for exchanging wireless power or wireless data with a device. [Figure 7A] FIG. 10 is a timing diagram of an exemplary variation of the interval-based powering method. [Figure 7B] FIG. 10 is a timing diagram of an exemplary variation of the interval-based powering method. [Figure 7C] FIG. 10 is a timing diagram of an exemplary variation of the interval-based powering method. [Figure 8] FIG. 10 is a timing diagram of an exemplary variation of the intermittent power supply method. [Figure 9] FIG. 10 illustrates an exemplary variation of a wireless system with an external wireless device comprising multiple arrays. [Figure 10] 1 is an exemplary schematic diagram of a spatial path of a first device (eg, an IMD) and a corresponding access period timing diagram. [Figure 11] FIG. 10 is a timing diagram of an exemplary variation of a physiological signal used to determine an access period. [Figure 12] 1 is a schematic block diagram of an exemplary variation of a first device (eg, an IMD) configured to select a transducer for operation. [Figure 13] 10 is a flowchart of an exemplary variation of a method for positioning a wireless device on a body. [Figure 14]10 is a flowchart of another exemplary variation of a method for positioning a wireless device on a body. [Figure 15] 10 is a flowchart of an exemplary variation of a method for coupling an ultrasound device to a patient's body. [Figure 16] 10 is a flowchart of an exemplary variation of a method for reducing noise. [Figure 17] 10 is a flowchart of another exemplary variation of a method for reducing noise. [Figure 18] 10 is a flowchart of an exemplary variation of a method for estimating heart rate. [Figure 19] FIG. 10 is a timing diagram of an exemplary variation of a method for estimating heart rate from a pressure signal. DETAILED DESCRIPTION OF THE INVENTION

[0055] I. System A. Overview Generally, systems, devices, and methods are described herein for establishing a wireless link between a set of devices, including at least one device disposed within a patient's body, and a wireless device, such as a device disposed externally to the patient. The systems described herein can include one or more wireless devices (e.g., implantable medical devices, ingestible devices, sensors, stimulators, etc.) disposed within the patient's body and an external device configured to be placed, for example, on the patient's skin. The wireless devices disposed within the body can be useful for one or more of monitoring, diagnosing, and treating diseases such as heart failure, prosthetic valve dysfunction, valvular heart disease, and restenosis. For example, monitoring a patient's physiological parameters (e.g., blood pressure) with a wireless device disposed within the body can be used to diagnose and / or monitor heart failure and / or other cardiovascular (CV) diseases.

[0056] In some variations, a wireless system may include one or more wireless devices, such as an implantable medical device (IMD) and an external wireless device. In some variations, the IMD may be implanted within a patient's body to perform one or more functions, such as monitoring physiological signals or parameters (e.g., blood pressure, blood flow, nerve action potentials, etc.) and stimulating tissue (e.g., nerves, muscles, etc.). In some variations, the IMD may be configured to receive wireless power from another wireless device. Additionally or alternatively, the IMD may include a power source (e.g., a capacitor, a battery, etc.) configured to be recharged by the external wireless device. In some variations, the IMD may be configured to wirelessly communicate data and / or commands bidirectionally with another wireless device. In such systems, establishing a reliable and / or efficient wireless link for power and / or data transfer may be important to minimize energy use (e.g., dissipation) of the IMD and the external wireless device, minimize tissue heating, and achieve error-free data transfer for accurate disease monitoring and treatment.

[0057] In some variations, a system for exchanging wireless power or wireless data can include an external wireless device with multiple transducer arrays, each configured to perform a distinct function. System efficiency can be improved by isolating the transducer arrays from one another so that their respective transducer configurations can be optimized. For example, a first transducer array of the external device can be configured to receive wireless signals from an IMD, and a processor can be configured to generate data based on the received wireless signals. A second transducer array can be configured to exchange one or more of power and data with the IMD.

[0058] In some variations, wireless power or wireless data exchange between an internal device (e.g., a first device) and an external device (e.g., a second device) can be interrupted when the internal device moves within the body or becomes misaligned relative to the external device. For example, if an IMD placed within the heart moves with the heartbeat, the external device may not reliably receive the feedback signal and the IMD may receive the interrogation signal inconsistently. In some variations of the systems, devices, and methods described herein, subarrays of external wireless devices can be cycled to transmit interrogation signals one by one until the received feedback signal meets a predetermined condition.

[0059] In some variations, the feedback signal generated by the IMD can include one or more of digital first device energy data and digital interrogation signal data. An external device receiving the feedback signal can be configured to select a transducer configuration for wireless power and wireless data exchange based on the feedback signal. This data in the feedback signal can enable one or more of locating the first device, establishing an efficient wireless link with the first device, and efficiently recharging the first device's power source, thereby reducing charging time and minimizing tissue heating. In some variations, the feedback signal can further include one or more analog pulses. In some variations, the transducer configuration can be selected based on one or more of time reversal, triangulation, and estimated strength of the feedback signal. In some variations, the processor can be configured to adjust one or more of the transmit power and transmit duration of the transducer configuration based on the feedback signal.

[0060] In some variations, an IMD placed within a patient's body can be more efficiently powered based on an interval-based powering method or an intermittent powering method. These methods can establish an efficient wireless link with a moving IMD, such as an IMD implanted in the heart. In some variations, the one or more transducer configurations can be selected based on time reversal. In some variations, selecting the one or more transducer configurations of the second device can include estimating a set of spatial coordinates of the first device using triangulation.

[0061] In some variations, the efficiency and reliability of the wireless link can be improved by identifying one or more transducers of an IMD that have the highest link gain with an external wireless device. For example, a system can include an IMD configured to receive a downlink signal from an external wireless device. One or more of the transducers of a first device can be configured to exchange one or more of wireless power and wireless data with a second device based on the received downlink signal.

[0062] An interrogation signal transmitted through a transmission medium, such as tissue, may generate reflections that can interfere with other signals, such as the feedback signal. In some variations, a received feedback signal transmitted by an IMD can be distinguished from reflections of the interrogation signal, thereby enabling accurate location of the IMD and subsequent establishment of a wireless link.

[0063] In some variations, a user (e.g., a patient) can position an external wireless device (e.g., a handheld device, a wearable device) on their body to establish a wireless link to the IMD (e.g., to recover physiological data from the IMD). Positional alignment between the external wireless device and the IMD can correspond to link efficiency and the ability to establish a reliable (e.g., robust) wireless link. In some variations, a method of positioning the wireless device on the body can include generating a user prompt corresponding to a desired location on the body and orienting the wireless device according to one or more of an orientation feature and an orientation signal of the wireless device. These and other methods can enable home monitoring by instructing (e.g., guiding) a user, such as a patient, on how to position the wireless device for disease monitoring and / or treatment.

[0064] In some variations, the position of a wireless device disposed on an external surface of the body can be estimated, and a user prompt can be provided to the user to manually align the wireless device with an internal device (e.g., an IMD). By aligning the wireless device with the internal device, the wireless link established therebetween can be improved. For example, a method of positioning a wireless device on the body can include measuring one or more parameters of the wireless device and the body, estimating a position of the wireless device on the body based on the measured parameters, and generating a user prompt corresponding to the estimated position of the wireless device on the body.

[0065] In some variations, an ultrasound device positioned on an external surface (e.g., skin) of a patient can be used to wirelessly power and / or communicate with an IMD using ultrasound signals. Proper coupling between the ultrasound device and the skin or tissue may be desired to efficiently exchange ultrasound signals inside and outside the body. In some variations, a method of coupling an ultrasound device to a patient's body can include measuring one or more parameters of the ultrasound device and the body and estimating a coupling status between the ultrasound device and the body based on the measured parameters. Based on the estimated coupling status, a user prompt corresponding to the coupling status between the ultrasound device and the body can be generated. This can enable automatic coupling status detection between the ultrasound device and the body. The user can be instructed on how to provide proper coupling between the ultrasound device and the body, thereby improving patient outcomes.

[0066] In some variations, an IMD configured to measure pressure can be configured to exchange ultrasonic signals, such as power and / or data, with an external wireless device. The ultrasonic signals propagate in the form of pressure waves and can couple with or interfere with the IMD's pressure signals, thereby corrupting physiological pressure data. In some variations, a method for reducing noise can include measuring parameters of ultrasonic signals received by one or more of an ultrasonic transducer, a pressure transducer, a flow sensor, a force sensor, and a microelectromechanical system (MEMS) device. Pressure data can be generated based on the pressure signal measured by the pressure transducer and the measured parameters of the ultrasonic signal. In some variations, the ultrasonic signal can be separated from the pressure signal, thereby enabling accurate recovery of physiological pressure data.

[0067] In some variations, a method for reducing noise can include receiving an ultrasonic signal using a pressure transducer of a device (e.g., an IMD) and filtering the ultrasonic signal using a filter coupled to the pressure transducer, thereby improving measurement of the pressure signal by attenuating the ultrasonic signal.

[0068] In some variations, the system can be configured to exchange wireless power or wireless data only during a predetermined access period corresponding to a portion of the spatial path of the first device (e.g., an IMD) that is not obstructed by tissue structures such as ribs or lungs. This can be useful to conserve energy in the external wireless device and / or the IMD and minimize tissue heating.

[0069] FIG. 1 is a schematic block diagram of an exemplary variation of a wireless system (100) comprising one or more devices (110, 114). The system (100) may comprise a first device (110) (e.g., a wireless device, an implantable medical device (IMD)) and a second device (114) (e.g., a wireless device, an external device). In some variations, the second device (114) may be located external to a patient's body or may be fully or partially implanted (e.g., under the skin). In some variations, one or more wireless signals, such as a downlink signal (140) and an uplink signal (150), may be exchanged between the second device (114) and the first device (110). The downlink signal (140) may include one or more of power, data, and other signals transmitted by the second device (114) to the first device (110). The uplink signal (150) may include one or more of data and other signals received by the second device (114) from the first device (110).

[0070] In some variations, the downlink signal (140) and the uplink signal (150) may be transmitted using one or more of mechanical waves (e.g., acoustic, ultrasonic, vibration), magnetic fields (e.g., inductive), electric fields (e.g., capacitive), electromagnetic waves (e.g., RF, optical), galvanic coupling, surface waves, etc. In some variations, the first device (110) and the second device (114) may comprise transducers (120) configured to transmit and / or receive wireless signals.

[0071] In some variations, the first device (110) (e.g., an IMD) may include a power circuit (160) that includes a power source (e.g., with energy storage capability), such as a battery, a capacitor, a combination thereof, or the like. In some variations, the power source of the first device may be recharged using wireless power transmitted by the second device (114). In some variations, one or more first devices (110) may be partially or fully powered or recharged by energy harvesting techniques, including one or more of vibration energy harvesting, cardiac motion, vascular wall motion, blood flow, thermal energy harvesting, chemical energy harvesting, a combination thereof, or the like.

[0072] In some variations, the first device (110) and the second device (114) may comprise a processor (130) that may be configured to perform one or more of: sending / receiving signals via the transducer (120), processing signals and / or data, combinations thereof, etc. In some variations, the first device (110) may further comprise one or more of a sensor configured to sense a parameter, such as a physiological parameter, and a stimulator configured to stimulate tissue.

[0073] In some variations, the first device (110) can be implanted in or on one or more of a cardiac structure (e.g., a heart chamber, a heart valve), a vascular structure (e.g., a pulmonary artery, any other blood vessel), etc. In some variations, the first device (110) can be coupled (e.g., attached) to another implantable device (e.g., a prosthetic heart valve, a stent, etc.). In some variations, the first device (110) can move and / or rotate relative to the second device (114) due to one or more of the pumping action of the heart, breathing, coughing, sneezing, lung movement, movement of other body organs or structures, movement of the implantable device, any movement of the first device, movement of a user (e.g., a patient, a nurse, a doctor) handling the second device, combinations thereof, etc. In some variations, the wireless system (100) can comprise multiple first devices (110) and / or multiple second devices (114).

[0074] B. Internal equipment Generally, a device (e.g., an implantable medical device, a wireless monitor, a first device) disposed within a patient's body as described herein can be configured to perform one or more of sensing, monitoring, stimulating, therapy delivery, etc. and can include one or more of the components described herein. In some variations, the device can include one or more of a transducer, a power circuit, a multiplexer, a processor, a memory, a sensor, a communication device (e.g., a wireless device), etc.

[0075] a. Transducer Generally, the transducer (120) described herein can be configured to convert signals between wireless energy modalities and electrical signals. In some variations, the transducer (120) can be configured to transmit and / or receive uplink and / or downlink signals. As described herein, the transducer (120) can be a component of one or more of the first device (110) and the second device (114). In some variations, the transducer (120) can comprise multiple transducer elements. The transducer (120) can include one or more arrays (e.g., subarrays), which can be separate transducer elements or can share common transducer elements.

[0076] In some variations, the transducer (120) can include one or more of an ultrasonic transducer, a radio frequency (RF) transducer (e.g., coil, RF antenna), a capacitive transducer, combinations thereof, etc. In some variations, the ultrasonic transducer can include one or more of a piezoelectric device, a capacitive micromachined ultrasonic transducer (CMUT), a piezoelectric micromachined ultrasonic transducer (PMUT), combinations thereof, etc. In some variations, the ultrasonic transducer can convert one or more of pressure and force into an electrical signal, and vice versa. In some variations, the transducer (120) can include one or more ultrasonic transducers, which can be of one or more types, including, but not limited to, piston (e.g., rod, plate), cylindrical, ring, spherical (e.g., shell), flexible (e.g., bar, diaphragm), flexural elastic, combinations thereof, etc. In some variations, the piezoelectric device can be made from one or more of lead zirconate titanate (PZT), PMN-PT, barium titanate (BaTiO), polyvinylidene fluoride (PVDF), lithium niobate (LiNbO), any derivatives thereof, or the like. In some variations, the ultrasonic transducer can be configured to receive power at a frequency between about 20 kHz and about 20 MHz. The frequency ranges described herein can allow the ultrasonic transducer to include millimeter or sub-millimeter dimensions. In some variations, the transducer (120) can include an RF transducer, such as a coil or antenna, that can be configured to transmit and / or receive one or more of power, data, and other signals.

[0077] In some variations, the transducer (120) may include one or more transducer elements (e.g., one or more arrays or subarrays of transducer elements) configured to receive downlink signals and / or transmit uplink signals. For example, the transducer (120) of the second device (114) may include one or more arrays (e.g., subarrays) of ultrasound transducer elements configured to transmit and / or receive ultrasound signals.

[0078] In some variations, a transducer (120) including multiple transducer elements can be configured to perform a predetermined set of functions. For example, a first transducer element can be configured to recover wireless power, a second transducer element can be configured to receive data or signals, and a third transducer element can be configured to transmit data or signals. In some variations, the transducer can be approximately 10 cm 3 The size of such a transducer can enable a compact (e.g., miniaturized) first device housing to aid in minimally invasive delivery of the first device into the body via percutaneous or transcatheter techniques. In some variations, the transducer (e.g., ultrasound transducer) of the first device can be physically oriented (e.g., angled) and positioned toward the transducer of the second device. This can improve the consistency, reliability, and energy efficiency of the exchange of wireless power and wireless data.

[0079] i. Ultrasonic transducer beam In some variations, the ultrasound transducer (120) of a wireless device (e.g., a first device, a second device) may comprise multiple ultrasound transducer elements configured to achieve a collective radiation pattern (e.g., a beam) with a wide acceptance angle (e.g., a 3 dB beamwidth). In some variations, one or more ultrasound transducer elements of a wireless device may have different sets of characteristics relative to one another that collectively form a radiation pattern with a wide acceptance angle. In some variations, the first device may be implanted in the body without precise knowledge of the orientation or position of the first device relative to the second device. For example, the orientation of one or more ultrasound transducers of the first device, or the orientation of the main lobe of one or more radiation patterns of the ultrasound transducers, may be unknown to the second device. For example, the first device may temporarily rotate after implantation due to movement of the first device relative to the second device (e.g., due to heartbeat, breathing, etc.), or the first device may slowly rotate relative to the tissue over time (e.g., over months or years). The systems, devices, and methods described herein can overcome these challenges in aligning a second device with a first device for reliable transfer of power and / or downlink signals.

[0080] In some variations, the set of characteristics may include, but is not limited to, the position, orientation, or angle of the transducer element relative to other elements (e.g., transducer elements on a flat substrate or transducer elements mounted in a particular structure at a predetermined angle relative to each other), the dimensions of the transducer element, the material of the transducer element, the polarization direction of the piezoelectric element, the polarization direction relative to the electrode location (e.g., a side electrode structure), combinations thereof, etc.

[0081] In some variations, the ultrasonic transducer may include three ultrasonic transducer elements oriented at a non-zero angle relative to one another (e.g., orthogonal, at a 30° angle relative to one another, etc.). For example, by orthogonalizing the three transducer elements to one another, each transducer element preferably receives wireless power from one of three orthogonal directions, thereby enabling one or more of power recovery from multiple directions (e.g., relatively omnidirectional power recovery) and a collective radiation pattern with a wide acceptance angle. In some variations, a set of three ultrasonic transducer elements may be arranged on a substrate (e.g., a PCB) within a compact module (e.g., using 3D assembly).

[0082] b.Power circuit In some variations, one or more ultrasonic transducer elements of the first device can be interfaced to a power circuit to receive power, as described in further detail herein. Generally, the power circuit (160) shown in FIG. 1 can be coupled to the transducer (120) of the first device (110) and can be configured to recover (e.g., regulate) the received wireless power, store the energy, and provide power for various operations of the first device. In some variations, the power circuit (160) can include one or more energy storage elements (e.g., batteries, capacitors) configured to store the energy received by the transducer. The power circuit can be configured to control (e.g., regulate, limit) the power provided to one or more components of the first device.

[0083] In some variations, the power circuit (160) can be configured to convert an alternating current (AC) voltage at the terminals of the transducer to a DC voltage (e.g., using a rectifier). In some variations, the power circuit (160) can be configured to recover wireless power received by a plurality of transducer elements disposed on the first device. For example, the power circuit coupled to the plurality of transducer elements can perform one or more of AC power coupling, DC power coupling, DC voltage coupling, DC current coupling, any combination thereof, etc.

[0084] In some variations, the power circuit (160) may include a power source including one or more of a capacitor, a supercapacitor, a rechargeable or secondary battery, a non-rechargeable or primary battery, combinations thereof, etc. In some variations, the power circuit (160) may include a rechargeable battery for energy storage with a capacitor in parallel with the battery, where the capacitor can sink / source at least a portion of the current during charge / discharge transients of the rechargeable battery.

[0085] In some variations, the power circuit (160) may not include a device for storing energy, and the first device may be simultaneously powered by another device (e.g., a second device, another IMD, etc.) while the first device is performing its function. In some variations, power may be supplied until the first device completes its function, and the first device may remain inactive until powered again.

[0086] In some variations, the systems, devices, and methods disclosed herein may include one or more of the systems, devices, and methods described in U.S. Patent No. 9,544,068, filed May 13, 2014; U.S. Patent No. 10,177,606, filed September 30, 2016; U.S. Patent No. 10,014,570, filed December 7, 2016; and U.S. Patent No. 9,774,277, filed November 13, 2013, the contents of each of which are incorporated herein by reference in their entirety.

[0087] c. Multiplexer circuit Generally, the multiplexers (e.g., multiplexer circuits) described herein can be configured to separate one or more of a power signal, a data signal, and other signals within a first device. Separating the signals can avoid interference between the signals and ensure proper functioning of the first device. For example, the multiplexer of the first device can be configured to separate a power signal from a data signal received from a second device such that the power signal is provided to a power circuit for power recovery and conditioning, while the data signal is provided to a processor for data recovery.

[0088] In some variations, the multiplexer may include a transmit / receive switch, a passive device (e.g., a diode, a relay, a MEMS circuit, a circuit breaker, a passive switch), a circulator, frequency selection (e.g., using a filter, an impedance matching network), a direct wired connection, a combination thereof, or the like.

[0089] d. Processor Generally, a processor (e.g., a CPU) described herein can receive, transmit, and / or process data and / or other signals and / or control one or more components of a system (e.g., an IMD). The processor can be configured to receive, process, compile, calculate, store, access, read, write, and / or transmit data and / or other signals. Additionally or alternatively, one or more elements of the processor of the first device (e.g., sensing and processing circuitry as discussed herein) may be configured to control one or more other elements of the processor (e.g., multiplexer circuitry, demultiplexer circuitry, etc.) and / or one or more components of the first device (e.g., transducers, power circuitry, memory, sensors, etc.). As described herein, the processor may be included in one or more of the first device, second device, etc.

[0090] In some variations, the processor may include data communications circuitry, which may be a data receiver, configured to access or receive data and / or other signals from one or more of a transducer, a sensor (e.g., a pressure sensor), and a storage medium (e.g., a memory, a flash drive, a memory card). For example, the processor may comprise one or more of a signal receiver (e.g., for detecting an interrogation signal), an envelope detector circuit, an amplifier (e.g., a low noise amplifier or LNA), a filter, a frequency detector circuit, a phase detector circuit, a comparator circuit, a decoder circuit, combinations thereof, etc., configured to receive data and / or signals through the transducer. In some variations, the processor of the first device may comprise monitoring circuitry configured to monitor one or more of a voltage, a current, a power, and an energy of the first device.

[0091] In some variations, a processor may include any suitable processing device configured to operate and / or execute a set of instructions or code, and may include one or more data processors, image processors, graphics processing units (GPUs), physical processing units, digital signal processors (DSPs), analog signal processors, mixed-signal processors, machine learning processors, deep learning processors, finite state machines (FSMs), compression processors (e.g., data compression to reduce data rates and memory requirements), encryption processors (e.g., for secure wireless data and / or power transfer), and / or central processing units (CPUs). Processors may include, for example, general-purpose processors, field-programmable gate arrays (FPGAs), application-specific integrated circuits (ASICs), processor boards, etc. The processor may be configured to operate and / or execute application processes and / or functions associated with other modules, systems, and / or processes. The underlying device technology may be provided in a variety of component types (e.g., metal-oxide-semiconductor field-effect transistor (MOSFET) technologies such as complementary metal-oxide-semiconductor (CMOS), bipolar technologies such as emitter-coupled logic (ECL), polymer technologies (e.g., silicon-conjugated polymer and metal-conjugated polymer-metal structures), mixed analog-digital, etc.

[0092] The systems, devices, and / or methods described herein may be implemented by software (executed on hardware), hardware, or a combination thereof. Hardware modules may include, for example, general-purpose processors (or microprocessors or microcontrollers), field-programmable gate arrays (FPGAs), and / or application-specific integrated circuits (ASICs). Software modules (executed on hardware) may be expressed in various software languages ​​(e.g., computer code), including C, C++, Java, Python, Ruby, Visual Basic, and / or other object-oriented, procedural, or other programming languages ​​and development tools. Examples of computer code include, but are not limited to, microcode or microinstructions, machine instructions such as those generated by a compiler, code used to generate web services, and files containing high-level instructions executed by a computer using an interpreter. Additional examples of computer code include, but are not limited to, control signals, encryption code, and compression code.

[0093] In some variations, the processor can be configured to process a signal (e.g., an interrogation signal) and take an action (e.g., generate a feedback signal). For example, the processor can include sensing and processing circuitry as described in detail herein. In some variations, the processor of the first device can be configured to process an interrogation signal that encodes an identification (ID) number of the first device and be able to decode the ID number. In such variations, the processor can be configured to decode or extract the ID number from the received interrogation signal and take an action (e.g., generate a feedback signal, take no action, etc.) depending on whether the ID in the interrogation signal matches the ID of the first device. In some variations, the processor of the first device can include one or more of an envelope detection circuit, an energy detector circuit, a power detector circuit, a voltage sensor, a time-to-digital converter (TDC) circuit, an integrator circuit, a sampling circuit, an analog-to-digital converter (ADC) circuit, a timer circuit, a clock, a counter, an oscillator, a phase-locked loop (PLL), a frequency-locked loop (FLL), combinations thereof, etc. for processing the interrogation signal received from the second device and generating the feedback signal.

[0094] In some variations, the processor of the wireless device may be configured to process signals (e.g., feedback signals), generate data (e.g., feedback signal data), and determine a transducer configuration (e.g., sub-array) of the wireless device for powering the first device, as described in detail herein. For example, the processor may comprise an amplifier, a phase detector, a frequency detector, a digital signal processor, an integrator, an adder circuit, a multiplier circuit, a finite state machine, combinations thereof, etc. to perform such calculations.

[0095] In some variations, the processor may comprise data communications circuitry, which may be a data transmitter, configured to generate or transmit data and / or other signals through one or more of a transducer, a storage medium, etc. For example, the processor of the first device may comprise one or more of a signal transmitter, an uplink data transmitter, an oscillator, a power amplifier, a mixer, an impedance matching circuit, a switch, a driver circuit, combinations thereof, etc. for generating or transmitting data and / or signals via a transducer.

[0096] In some variations, the processor may be configured to control one or more elements within the first device and / or the second device. For example, the processor may be configured to control the first device to generate a feedback signal or perform a sensing function in response to a command received from the second device via a downlink signal.

[0097] In some variations, the first processor may be a component of the first device, and the second processor may be a component of the second device. In such variations, the first device may be configured to receive an interrogation signal, and the first processor may be configured to process the interrogation signal and generate a feedback signal. The second processor may be configured to process the feedback signal received by the second device, generate feedback signal data, and determine a transducer configuration of the second device as described in detail herein. In some variations, the first processor of the first device may be configured to process one or more interrogation signals and determine a transducer configuration (e.g., a transducer configuration of the second device that resulted in the maximum power of the interrogation signal at the first device) based on the interrogation signals.

[0098] e.Memory Generally, the first device and / or the second device described herein can include a memory configured to store data and / or information. In some variations, the memory includes one or more types including, but not limited to, random access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), resistive random access memory (ReRAM or RRAM), magnetoresistive random access memory (MRAM), ferroelectric random access memory (FRAM), standard cell-based memory (SCM), shift register, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), flash memory (e.g., NOR, NAND), embedded flash, volatile memory, non-volatile memory, one-time programmable (OTP) memory, combinations thereof, etc.

[0099] In some variations, the memory can be configured to store instructions and / or data that cause the processor to execute modules, processes, and / or functions (e.g., executing a search algorithm) associated with the first device and / or the second device. Some variations described herein may relate to computer storage products having non-transitory computer-readable media (sometimes referred to as non-transitory processor-readable media) having instructions or computer code for performing various computer-implemented operations. The computer-readable media (or processor-readable media) may be non-transitory in the sense that they do not themselves contain transient propagating signals (e.g., propagating electromagnetic waves that carry information over a transmission medium such as space or a cable). The media and computer code (sometimes referred to as code or algorithms) may be designed and constructed for a specific purpose or purposes.

[0100] In some variations, the memory can be configured to store sensor data, received data, and / or data generated by the first device and / or the second device. In some variations, the memory of the first device can be configured to store data generated during processing of signals sensed by a sensor (e.g., blood pressure data sensed by a pressure sensor that may be included in the first device). In some variations, the memory of the first device can be configured to store one or more of parameters of an interrogation signal, parameters of a feedback signal, parameters related to power received by the first device, parameters related to the movement and / or rotation or orbit of a moving IMD, etc.

[0101] In some variations, the memory of the second device can be configured to store one or more of interrogation signal parameters, feedback signal parameters, feedback signal data, data corresponding to transducer configurations, patient data, wireless system data (e.g., the number and / or location of IMDs, the spatial path of one or more IMDs, one or more identification (ID) numbers corresponding to one or more IMDs), combinations and derivatives thereof, etc. In some variations, the memory of the first device and / or the second device can be configured to store image data including 2D, 3D, Doppler, and any other data generated from patient imaging (e.g., thoracic or tissue images, echocardiography images, MRI images). In some variations, the memory can be configured to store data temporarily or permanently.

[0102] f. Sensor Generally, the sensors described herein can be configured to sense or measure one or more parameters, such as, but not limited to, physiological parameters of a patient. In some variations, the sensors may be pressure sensors, flow sensors, transducers (e.g., ultrasound transducers, infrared / optical photodiodes, infrared / optical LEDs, RF antennas, RF coils), temperature sensors, electrical sensors (e.g., using electrodes to measure impedance, electromyogram or EMG, electrocardiogram or ECG, etc.), magnetic sensors (e.g., RF coils), electromagnetic sensors (e.g., infrared photodiodes, optical photodiodes, RF antennas), neural sensors (e.g., for sensing neural action potentials), force sensors (e.g., strain gauges), flow or velocity sensors (e.g., hot wire anemometers, vortex sensors, etc.). The device may include one or more of the following: a flow meter), an acceleration sensor (e.g., an accelerometer), an activity sensor (e.g., for monitoring the patient's activity level), a chemical sensor (e.g., a pH sensor, a protein sensor, a glucose sensor), an oxygen sensor (e.g., a pulse oximetry sensor, a myocardial oxygen consumption sensor), an audio sensor (e.g., a microphone for detecting heart murmurs, prosthetic valve noise, auscultation), sensors for measuring other physiological parameters (e.g., sensors for sensing heart rate, respiratory rate, arrhythmias, heart wall motion), a stimulator (e.g., for stimulation and / or pacing functions), combinations thereof, and the like.

[0103] In some variations, one or more pressure sensors (also referred to as pressure transducers) can be used to monitor cardiovascular diseases such as heart failure. In some variations, the one or more pressure sensors may include, but are not limited to, absolute pressure sensors, gauge pressure sensors, sealed pressure sensors, differential pressure sensors, atmospheric pressure sensors, combinations thereof, etc. In some variations, the one or more pressure sensors may be based on one or more pressure sensing technologies, including, but not limited to, resistive (e.g., piezoresistive using a strain gauge or membrane to create a pressure-sensitive resistance), capacitive (e.g., using a diaphragm or membrane to create a pressure-sensitive capacitance), piezoelectric, optical, resonant (e.g., pressure-sensitive resonant frequency of a structure), combinations thereof, etc. In some variations, the pressure sensors may be fabricated using microelectromechanical systems (MEMS) technology.

[0104] In some variations, the sensors may include stimulators (e.g., electrical stimulators) used to stimulate muscles and / or neurons or nerves of the body. For example, one or more stimulators may be configured to stimulate the ventricular wall for pacing and / or cardiac resynchronization.

[0105] g. Spatial path The spatial path of a first device (e.g., an IMD) can generally refer to a set of positions (e.g., a path, a trajectory) and / or a set of orientations that the first device traverses relative to a second device (e.g., an external wireless device). For example, the first device may move and / or rotate relative to the second device. The spatial path of the first device may include one or more of a line, a curved path, a rotation, a tilt, a combination thereof, and the like. In some variations in which the first device may be implanted in or near cardiac tissue or cardiovascular structures, the spatial path of the first device may also be referred to as a cardiac path. The motion of the first device may be due to one or more of the pumping motion of the heart, breathing, movement of the lungs, movement of other body organs or structures, movement of the external wireless device, any movement of the first device, movement of a user (e.g., a patient, a nurse, a doctor) handling the external wireless device, combinations thereof, and the like.

[0106] h. Operation mode A first device (e.g., an IMD) described herein can be configured to operate in one or more modes, including, but not limited to, a stimulation mode, a sensing mode, a wireless downlink mode, a wireless uplink mode, a sleep mode, combinations thereof, etc. The sensing mode may include one or more of: sensing or sampling (e.g., periodically) a parameter to generate a sensor signal; conditioning the sensor signal; digitizing the sensor signal to generate a digitized signal; combinations thereof; etc. The wireless downlink mode can include a mode in which the first device can be configured to receive power, data, one or more signals (e.g., interrogation signals), one or more commands, combinations thereof, etc. The wireless uplink mode can include a mode in which the first device can be configured to transmit or generate one or more of uplink data (e.g., processed data), one or more wireless signals (e.g., active uplink signals, reflected signals, modulated backscatter signals, etc.), combinations thereof, etc. In the sleep mode, the first device can be configured not to perform any active function (e.g., sensing, stimulation, etc.) and to wait for an instruction or an interrogation signal from the second device.

[0107] i. Placement of the first device within the body Generally, the implantable devices described herein can be configured to be placed (e.g., implanted) within a patient's or animal's body. In some variations, a first device, as described herein, may be a standalone device. In some variations, a first device, as described herein, may be coupled (e.g., attached) to another device placed within the body. For example, one or more first devices may be coupled to a prosthetic heart valve or stent. As another example, one or more first devices may be coupled to one or more of a pulse generator and one or more leads of a pacemaker, an implantable cardioverter-defibrillator, and / or a cardiac resynchronization therapy device.

[0108] In some variations, the first device may be coupled to one or more of a prosthetic heart valve, a prosthetic heart valve conduit, a valve leaflet coaptation device, an annuloplasty ring, a valve repair device (e.g., clip, stent), a septal occluder, an adnexal occluder, a ventricular assist device, a pacemaker (e.g., including leads, a pulse generator), an implantable cardioverter defibrillator (e.g., including leads, a pulse generator), a cardiac resynchronization therapy device (e.g., including leads, a pulse generator), an insertable cardiac monitor, a stent (e.g., a coronary or peripheral stent, a fabric stent, a metal stent), a stent graft, a scaffold, an embolic protection device, an embolic coil, an intravascular plug, a vascular patch, a vascular closure device, an atrial shunt, a parachute device for treating heart failure, a cardiac loop recorder, combinations thereof, etc. For example, the prosthetic heart valve may include one or more of a transcatheter heart valve (THV), a self-expanding THV, a balloon-expandable THV, a surgical bioprosthetic heart valve, a mechanical valve, etc.

[0109] Generally, the implantable devices described herein can be positioned in or near any region of the body, including, but not limited to, a heart valve (e.g., aortic valve, mitral valve), a heart chamber (e.g., left ventricle, left atrium, right ventricle, right atrium), a blood vessel (e.g., pulmonary artery, aorta, superficial femoral artery, coronary artery, pulmonary vein, etc.), cardiac tissue (e.g., myocardium or heart wall, septum), gastrointestinal tract (e.g., stomach, esophagus), bladder, combinations thereof, etc.

[0110] C. Second Device Generally, as used herein, a second device (e.g., wireless device, external wireless device) can refer to any device that is physically separate from one or more first devices (e.g., IMDs). In some variations, the second device (114) can include a transducer (120) and a processor (130), for example, as shown in FIG. 1 . In some variations, the second device can include memory as described herein. In some variations, the second device can include a battery for storing energy that can be used to wirelessly power and / or communicate with one or more first devices and / or communicate with one or more other second devices (e.g., tablet, phone, laptop, computer, server, database, network).

[0111] In some variations, the transducer (120) of the second device (114) may include multiple ultrasonic transducer elements, which may include multiple configurations for exchanging (transmitting and / or receiving) wireless signals with one or more IMDs, as described in detail herein. In some variations, the second device may comprise one or more transducer arrays (e.g., subarrays, transducer elements). In some variations, the one or more transducers or transducer elements of the second device may include one or more of an ultrasonic transducer, a radio frequency (RF) transducer (e.g., a coil, an RF antenna), a capacitive transducer, combinations thereof, etc. In some variations, the processor (130) of the second device (114) may be configured to process wireless signals (e.g., feedback signals) received from the first device.

[0112] In some variations, the second device may be configured to perform one or more functions including, but not limited to, transmitting wireless power, data, and other signals (e.g., interrogation signals) to one or more first devices (e.g., IMDs), receiving one or more of wireless data and other signals (e.g., feedback signals) from one or more first devices, processing data and / or signals (e.g., processing feedback signals), performing sensing and / or actuation (e.g., measuring blood pressure, heart rate, heart rate variability, ECG, EKG, thoracic impedance, respiratory rate or respiration, patient activity level, heart sounds, lung sounds, temperature, weight, blood glucose, blood oxygen), storing data or information in memory, communicating with other wireless devices (e.g., tablets, phones, computers) using wired and / or wireless links (e.g., Bluetooth), displaying or providing data or information (e.g., visual display on a screen or monitor, audio signal), generating alerts / notifications (e.g., visual, audio, vibration) to a user (e.g., patient, physician), combinations thereof, etc.

[0113] In some variations, the second device may be located in one or more locations, including, but not limited to, outside the body (e.g., a wearable device, a strap, a belt, a handheld device, a probe coupled to a measurement setup, a device placed on the skin, a device attached to the skin using an adhesive, a device attached to the skin using other techniques, a device that does not touch the patient, a laptop, a computer, a mobile phone, a smartwatch, etc.), permanently implanted in the body (e.g., under the skin, along the outer wall of an organ), temporarily implanted in the body (e.g., placed on a catheter or probe inserted through a blood vessel, the esophagus, or the chest wall, used during surgery or a procedure), combinations thereof, etc. In some variations, the second device may have a different shape or form, including, but not limited to, planar, conformal to the body or organ, flexible, stretchable, flat, probe-like, etc. In some variations, the second device may perform a function for another second device (e.g., process feedback signals). For example, a second device located on the patient's body (e.g., located on the chest) can communicate feedback signal data generated from feedback signals received from one or more IMDs to another second device, such as a laptop, tablet, mobile phone, etc. This other second device can process the feedback signal data, execute search algorithms, and / or perform calculations (e.g., determine a transducer configuration for powering the first device).

[0114] In some variations, the second device may further include a communications device configured to enable a user and / or medical professional to control one or more of the devices of the wireless system. The communications device may include a network interface configured to connect the second device to another system (e.g., the Internet, a remote server, a database) via a wired or wireless connection. In some variations, the second device may communicate with other devices (e.g., a mobile phone, a tablet, a computer, a smartwatch, etc.) via one or more wired and / or wireless networks. In some variations, the network interface may include one or more of a radio frequency (RF) receiver, an RF transmitter, an optical (e.g., infrared) receiver, an optical transmitter, an acoustic or ultrasonic receiver and transmitter, etc. configured to communicate with one or more devices and / or networks. The network interface may communicate with one or more of a wireless device, a network, a database, and a server via a wired and / or wireless connection.

[0115] The network interface may include RF circuitry configured to receive and / or transmit RF signals. The RF circuitry converts electrical signals to electromagnetic signals (and vice versa) and communicates with communication networks and other communication devices via electromagnetic signals. The RF circuitry may include well-known circuits for performing these functions, including, but not limited to, an antenna system, an RF transceiver, one or more amplifiers, a tuner, one or more oscillators, a mixer, a digital signal processor, a CODEC chipset, a subscriber identity module (SIM) card, memory, etc.

[0116] Wireless communication through any of the devices described herein may be via any of the following technologies: Global System for Mobile Communications (GSM), Enhanced Data for Global System for Mobile Communications (EDGE), High Speed ​​Downlink Packet Access (HSDPA), High Speed ​​Uplink Packet Access (HSUPA), Evolution Data Only (EV-DO), HSPA, HSPA+, Dual Cell HSPA (DC-HSPA), Long Term Evolution (LTE), Near Field Communications (NFC), Wideband Code Division Multiple Access (W-CDMA), Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Bluetooth, Wireless Fidelity (WiFi) (e.g., IEEE 802.11a, IEEE 802.11b, IEEE 802.11g, IEEE Any of a number of communication modalities, standards, protocols, and technologies may be used, including, but not limited to, 802.11n, Voice over Internet Protocol (VoIP), Wi-MAX, protocols for email (e.g., Internet Message Access Protocol (IMAP) and / or Post Office Protocol (POP)), instant messaging (e.g., Extensible Messaging and Presence Protocol (XMPP), Session Initiation Protocol for Instant Messaging and Presence Enhancements (SIMPLE), Instant Messaging and Presence Service (IMPS)), and / or Short Message Service (SMS), or any other suitable communication protocol. In some variations, devices herein may communicate directly with each other without transmitting data over a network (e.g., via NFC, Bluetooth, WiFi, RFID, etc.).

[0117] The communication device may further comprise a user interface configured to enable a user (e.g., patient, subject, partner, family member, medical professional, etc.) to control the second device. The communication device may enable the user to directly and / or remotely interact with and / or control the second device. For example, the user interface of the second device may include an input device through which the user inputs commands and through which the user receives output (e.g., a blood pressure reading on a display device).

[0118] In some variations, the second device may include an output device and a user interface. The output device of the user interface may output one or more of data corresponding to the coupling of the second device to tissue or skin, data corresponding to a wireless link between the second device and the first device (e.g., a reliable link has been established), the movement, rotation, and / or trajectory of one or more IMDs, etc., and may include one or more of a display device and an audio device. Data analysis generated by the server may be displayed by an output device (e.g., a display) of the second device. Data used to select a transducer configuration or ensure that the second device is optimally coupled to the tissue may be received through the communication device and output visually and / or audibly through one or more output devices of the second device. In some variations, the output device may include a display device including at least one of a light-emitting diode (LED), a liquid crystal display (LCD), an electroluminescent display (ELD), a plasma display panel (PDP), a thin-film transistor (TFT), an organic light-emitting diode (OLED), an e-paper / e-ink display, a laser display, and / or a holographic display.

[0119] The audio device may audibly output one or more of any data, commands, instructions, prompts, warnings, notifications, etc. For example, the audio device may output an audible warning when a link between a first device and a second device is interrupted or disconnected, prompting manual adjustment by a user. In some variations, the audio device may include at least one of a speaker, a piezoelectric audio device, a magnetostrictive speaker, and / or a digital speaker. In some variations, a user may communicate with other users using the audio device and the communication channel. For example, a user may use the second device and another device to form an audio communication channel (e.g., a VoIP call) with a remote medical professional.

[0120] In some variations, the user interface may include an input device (e.g., a touchscreen) and an output device (e.g., a display device) and may be configured to receive input data from one or more of a first device, a second device, a network, a database, and a server. For example, user control of the input device (e.g., a keyboard, a button, a touchscreen) may be received by the user interface, which may then be processed by a processor and memory to output a control signal to the first device. Some variations of the input device may include at least one switch configured to generate a control signal. For example, the input device may include a touch surface through which a user provides input (e.g., a finger touch on the touch surface) corresponding to the control signal. An input device including a touch surface may be configured to detect contact and movement on the touch surface using any of a number of touch-sensing technologies, including capacitive, resistive, infrared, optical imaging, dispersive signal, acoustic pulse recognition, and surface acoustic wave technologies. In variations of input devices that include at least one switch, the switch may include, for example, at least one of a button (e.g., hard key, soft key), a touch surface, a keyboard, an analog stick (e.g., a joystick), a directional pad, a mouse, a trackball, a jog dial, a step switch, a rocker switch, a pointer device (e.g., a stylus), a motion sensor, an image sensor, and a microphone. The motion sensor can receive user motion data from an optical sensor and classify the user's gestures as control signals. The microphone can receive audio data and recognize the user's voice as a control signal.

[0121] A haptic device can be incorporated into one or more of the input and output devices to provide additional sensory output (e.g., force feedback) to the user. For example, the haptic device can generate a haptic response (e.g., vibration) to confirm a user input to the input device (e.g., a touch surface). As another example, the haptic feedback may notify that the user input is overridden by a second device.

[0122] a. Subarray A subarray can generally refer to any subset of the plurality of transducer elements of the second device. In some variations, a subarray may include a set of adjacent transducer elements of a transducer array, an alternating set of transducer elements (e.g., every other element), a set of every “n” transducer elements, or any subset of transducer elements. For example, a subarray may include a set of transducer elements selected to efficiently transfer wireless power to the first device based on a feedback signal, as described in detail herein. In some variations, a subarray may include a single transducer element of the second device. In some variations, a subarray may include all transducer elements of the second device.

[0123] In some variations, subarrays may include disjoint sets of transducer elements. For example, the second device may include a linear 1D array with array elements labeled 1, 2, 3, etc., and subarrays may be comprised of element numbers 1-8, 9-16, 17-24, etc. In some variations, subarrays may include overlapping sets of transducer elements. For example, in the example of a linear 1D array, subarrays may be comprised of element numbers 1-8, 2-9, 3-10, etc. In some variations, the sizes of the subarrays may vary. For example, different subarrays of the same second device may include one or more of different numbers of transducer elements (e.g., some subarrays may include four transducer elements, some subarrays may include 16 transducer elements), differently sized transducer elements, combinations thereof, etc. In some variations, the selection of transducer elements for a given subarray of the second device may be based on feedback signal data, as described in detail herein.

[0124] b. Transducer configuration A transducer configuration may generally refer to one or more transducer elements of a second device configured to exchange one or more of wireless power and wireless data with a first device (e.g., to recharge the power source of the first device). A transducer configuration may also refer to parameters and settings of one or more transducer elements configured to drive signal transmission (e.g., frequency, amplitude, phase, time delay, duration, etc. by which one or more transducer elements may be configured to transmit signals) and signal reception (e.g., phase shift, time delay, gain, etc. by which one or more transducer elements may be configured to receive signals). In some variations, the transducer configuration may be selected by a processor of the second device based on a feedback signal received from the first device.

[0125] In some variations, a transducer configuration configured to transmit wireless signals to a first device may be referred to as a transmit transducer configuration (TTC). In some variations, a transducer configuration configured to receive wireless signals from a first device may be referred to as a receive transducer configuration (RTC). In some variations, a transducer configuration selected by a processor of a second device based on a feedback signal received from a first device may be referred to as an optimal transducer configuration (OTC), which may be improved compared to a default transducer configuration, but is not necessarily the most suitable transducer configuration. In some variations, a set of transducer elements of a wireless device that can be selectively configured to power a wireless monitor and / or transmit other downlink signals to the wireless monitor, along with the drive signals for each of those transducer elements, may be collectively referred to as a sub-array power snapshot. In some variations, a set of transducer elements of a wireless device configured to receive an uplink signal (e.g., data) from an IMD, along with parameters related to reception of the signal and conditioning of the received signal, such as gain, phase shift, delay, filtering, time window for receiving the signal, etc., may be collectively referred to as a sub-array uplink data snapshot.

[0126] c. User prompts A user prompt (also referred to as user feedback) may generally refer to one or more instructions, notifications, recommendations, warnings, etc. provided to a user by a second device. A user prompt may serve many purposes, including, but not limited to, communicating data regarding the state of charge (SoC) and / or depth of discharge (DoD) of the batteries of the first device and / or the second device, prompting the user to recharge the battery of the second device, communicating data regarding data transfer between the first device and the second device (e.g., data transfer completion rate), prompting the user to manually adjust or reposition the second device on the patient's body, combinations thereof, etc. In some variations, a user prompt may be provided using a visual indication, an audio indication, a vibration, a notification (e.g., an alert on a phone, computer, etc., a push notification, email, etc.), combinations thereof, etc. As described herein, variations of communication devices, user interfaces, input devices, output devices, etc. may be used to provide user prompts.

[0127] In some variations, the user prompts (e.g., visual instructions) may include one or more of: images, photographs, and stylized representations (e.g., diagrams, cartoons, schematics) of the patient's chest (e.g., showing one or more of the chest, arms, neck, and head); a current device configuration (e.g., position, angle, tilt, etc.) of the second device; a target device configuration (e.g., position, angle, rotation, tilt, etc.) of the second device; a map showing the current / target location; instructions displayed in text form (e.g., a statement asking the user to move the second device toward the patient's left arm, right arm, head, etc.; a number or percentage representing the power received by the first device; the battery's SoC and / or DoD; etc.); arrows guiding the user to move, rotate, and / or adjust the second device; LEDs (e.g., steady, flashing); combinations thereof; and the like. For example, in some variations, the current and target locations of the wireless device may be superimposed on an image of the chest. The user may be instructed to move the second device until it reaches the target location.

[0128] In some variations, the audio instructions may include one or more of a voice command (e.g., asking the user to move the second device toward the patient's left arm, asking the user to recharge the battery of the second device, notifying the user that data transfer from the first device to the second device is complete), a beep, an alarm, a combination thereof, etc.

[0129] d. Network In some variations, the systems, devices, and methods described herein can communicate with other wireless devices via one or more networks, each of which may be any type of network (e.g., wired network, wireless network). Communications may or may not be encrypted. A wireless network may refer to any type of digital network that is not connected by any type of cable. Examples of wireless communications in a wireless network include, but are not limited to, cellular, radio, satellite, and microwave communications. However, a wireless network may be connected to a wired network to interface with the Internet, other carrier voice and data networks, business networks, and personal networks. Wired networks are typically carried via copper twisted pair, coaxial cable, and / or fiber optic cable. Many different types of wired networks exist, including wide area networks (WANs), metropolitan area networks (MANs), local area networks (LANs), Internet area networks (IANs), campus area networks (CANs), global area networks (GANs) such as the Internet, and virtual private networks (VPNs). Hereinafter, a network refers to any combination of wireless, wired, public, and private data networks that are typically interconnected through the Internet to provide an integrated network and information access system.

[0130] Cellular communications may encompass technologies such as GSM, PCS, CDMA or GPRS, W-CDMA, EDGE or CDMA2000, LTE, WiMAX, and 5G network standards. Some wireless network deployments combine multiple cellular networks or use a mix of cellular, Wi-Fi, and satellite communications. In some variations, the network can be used for remote processing of any data or information used by the wireless system described herein. For example, a processor capable of processing any data or information related to the wireless system may be located in the same housing as the first device and / or the second device, in a separate housing in the same room or building as the first device, in a remote location (e.g., different building, city, country) from the first device and the second device, any combination thereof, etc. Processing of data or information related to the wireless system may be performed in real time as data (e.g., feedback signal data, physiological data) is received or recorded, or may be performed at different times.

[0131] D. Wireless Signals As used herein, a wireless signal may generally refer to any wireless signal exchanged between at least two devices, such as a first device and a second device. In some variations, the wireless signal may include one or more of a power signal, a downlink data signal, an interrogation signal, a feedback signal, an uplink data signal, a reflected signal, a backscattered signal, etc. For example, in some variations, a wireless signal generated by a first device may include a reflected signal or a backscattered signal from the first device that is generated upon incidence of a downlink signal, such as an interrogation signal, on the first device.

[0132] a. Interrogation signal An interrogation signal may generally refer to any signal transmitted by a second device or by one or more other methods during an interrogation process of a first device, as described in more detail herein. For example, an interrogation signal may refer to any signal transmitted by a sub-array of a second device configured to elicit a feedback signal from the first device. In some variations, the interrogation signal may be one or more of a power signal configured to transfer wireless power to the first device, a downlink data signal configured to transfer data / commands to the first device, and any other signal configured to elicit feedback from the first device, combinations thereof, etc.

[0133] In some variations, the interrogation signal may be generated using one or more of mechanical waves (e.g., ultrasound, acoustic, vibration), magnetic fields (e.g., inductive), electric fields (e.g., capacitive), electromagnetic waves (e.g., RF, optical), galvanic coupling, surface waves, etc. In some variations, the interrogation signal may be generated in the form of a continuous wave (CW) signal or a pulsed wave (PW) signal. In some variations, the interrogation signal may be generated using any known digital or analog modulation technique, such as ASK, FSK, PSK, AM, FM, PM, pulse modulation, PAM, PIMD, PPM, PCM, PDM, etc. In some variations, the ultrasonic interrogation signal may include a carrier frequency of about 20 kHz to about 20 MHz.

[0134] In some variations, the interrogation signal may encode a unique identification (ID) number or code corresponding to one or more wireless devices (e.g., IMDs). For example, the ID number may be configured to instruct one or more predetermined IMDs to respond to the interrogation signal. In some variations, the interrogation signal may encode a command corresponding to one or more functions of the first device. For example, in some variations, the interrogation signal may encode a command, and upon receiving the command, the first device may configure itself to send a feedback signal to the second device. In some variations, the interrogation signal may encode a command, and upon receiving the command, the first device may configure itself to receive wireless power from the second device and / or recharge its power source, such as a battery or capacitor. In some variations, the interrogation signal may encode a command, and upon receiving the command, the first device may configure itself to transmit data to the second device via an uplink signal. In some variations, the interrogation signal may encode a command, and upon receiving the command, the first device may configure itself to operate in one or more operating modes, such as a sensing mode, a stimulation mode, a sleep mode, a combination thereof, etc.

[0135] b. Feedback signal A feedback signal may generally refer to any signal received by a second device from a first device. In some variations, a feedback signal may be generated in response to another signal (e.g., an interrogation signal). In some variations, a first device (e.g., an IMD) may be configured to transmit one or more feedback signals without being interrogated by a second device. For example, a first device may be configured to periodically transmit a feedback signal, which may also be referred to as a beacon signal in some variations.

[0136] In some variations, the feedback signal can include similar parameters (e.g., type, waveform shape, modulation, etc.) as those described with respect to the interrogation signal. For example, the feedback signal can include an ultrasonic pulse having a carrier frequency of about 20 kHz to about 20 MHz.

[0137] In some variations, the feedback signal transmitted by the first device in response to receiving the interrogation signal may include one or more pulses. For example, in some variations, after receiving the interrogation signal, the first device may transmit a single ultrasonic pulse (e.g., comprising one or more cycles of a carrier frequency), or the first device may periodically transmit multiple ultrasonic pulses. Such ultrasonic pulses may be used by the second device for triangulation or localization of the first device and / or estimation of link gain between the second device and the first device, as described in more detail herein.

[0138] In some variations, the feedback signal may include data encoded using any modulation technique (e.g., digital modulation). For example, in some variations, the first device may encode into the feedback signal, including, but not limited to, the power or voltage received by one or more transducers of the first device due to the interrogation signal (e.g., after digitization of the power or voltage), the voltage of the battery and / or capacitor of the first device, the energy state of the first device, the energy stored in the power source (e.g., battery, capacitor) of the first device, the battery charging current, the DC voltage generated by the power circuit of the first device after rectifying the interrogation signal, combinations thereof, etc. As another example, in some variations, the first device may encode a unique ID or code into the feedback signal. In some variations, the feedback signal may encode a time delay. For example, in some variations, the feedback signal may encode a time delay (e.g., after digitization) between receiving the interrogation signal from the second device and transmitting the feedback signal to the second device.

[0139] In some variations, the feedback signal may include one or more of a reflected signal and a backscattered signal. These signals may be generated upon reflection or backscattering of the interrogation signal or other signal transmitted by the second device from one or more first devices and / or one or more tissue structures (e.g., ribs, lungs, boundaries between two tissue types, etc.). Reflections from the first device may include one or more reflections from one or more of the first device's housing, coatings or sealants, the first device transducer (e.g., ultrasound transducer), a surface of the first device (e.g., front, back, side, exterior, interior), any portion of the first device, combinations thereof, etc. In some variations, the reflected signal may include an ultrasound reflected signal generated upon reflection of an ultrasound signal transmitted by a subarray of the second device from tissue.

[0140] c. Feedback signal data Feedback signal data may generally refer to any characteristics of the feedback signal as received by the second device and / or any data generated upon processing of the feedback signal by a processor of the second device. In some variations, such characteristics of the feedback signal may include one or more of phase, time of arrival, time delay, amplitude, intensity, power or energy, frequency, number of pulses, any data or information that can be encoded into the feedback signal (e.g., digitized battery voltage of the first device, a unique ID of the first device, etc.), combinations or derivatives thereof, etc. The feedback signal data may be generated corresponding to one or more transducer elements of the second device. In some variations, the feedback signal data may include data obtained from processing currently and / or previously received feedback signals.

[0141] E. Wireless Power and Data Exchange Described herein are systems configured to exchange wireless power or wireless data between two devices, such as between an implantable medical device (IMD) and a second device (e.g., an external wireless device). Localization of the first device (i.e., estimation of the location of the first device within tissue) can help the two devices reliably and efficiently exchange power or data, since the exact location of the first device may not be known after implantation. Once the location of the first device is determined, wireless signals can be focused to the location of the first device. This can be particularly important when exchanging ultrasound power or data due to the short wavelength of ultrasound in tissue, but can also be useful for other wireless systems, such as systems using RF power or data.

[0142] 2 illustrates an exemplary variation of a system including a first device (210) implanted in the heart surrounded by tissue (270) and ribs (272) along with an external second device (214) comprising one or more arrays (220) of transducer elements (222). In some variations, the second device (214) may be positioned on the patient's chest. The second device (214) may be configured to transmit a downlink signal, such as an interrogation signal (242), to the first device (210). The first device (210) may be configured to generate a wireless signal, such as a feedback signal (252), including one or more of an uplink signal transmitted by the first device (210), a reflected signal from the first device (210), a backscattered signal from the first device (210), etc. In some variations, the first device (210) may move relative to the second device (214) along a spatial path (280) or a periodic orbit.

[0143] 3A, 3B, and 3C illustrate exemplary variations of a system configured to exchange wireless power or wireless data between a first device (310) and a second device (314). The system may include a first device (310) and a second device (314), which may include a processor (not shown) and a transducer array (320) including multiple subarrays. In some variations, the transducer array (320) may include an ultrasound transducer array. In some variations, the first device (310) may be surrounded (e.g., surrounded) by tissue (370) and ribs (372). In some variations, the first subarray (324) of the transducer array (320) may be configured to transmit an interrogation signal (342) to the first device (310), as shown in FIG. 3A. For example, the first subarray (324) may include a single transducer element, as highlighted in FIG. 3A, or a subset of the transducer elements of the transducer array (320). In some variations, the second subarray (326) may be configured to receive a feedback signal (352) from the first device (310), as shown in FIG. 3B. For example, the second subarray (326) may include each of the transducer elements of the transducer array (320), or a subset of the transducer elements of the transducer array (320), as highlighted in FIG. 3B. In some variations, the processor of the second device may be configured to select a transducer configuration (328) based on the feedback signal (352) received by the second subarray (326), as shown in FIG. 3C. In some variations, as shown in Figure 3C, the transducer arrangement (328) can be configured to transmit a power signal (344) to the primary device (310). Generally, the transducer arrangement (328) can be configured to exchange one or more of wireless power and wireless data with the primary device (310).Such systems and processes may be useful for optimizing link efficiency and reliability of power and data transfer between a first device and a second device.

[0144] a. Interrogation signal Different variations of the interrogation signal used to interrogate the first device are described herein. In some variations, performing the interrogation of the first device within a limited period of time may be advantageous for quickly completing the power / data transfer process. In some of these variations, the first device may configure a wireless system to quickly and reliably detect when the second device transmits an interrogation signal to the first device. However, because the exact location of the first device may initially be unknown and due to the presence of heterogeneous tissue structures and tissue loss, the strength of the interrogation signal at the first device may be below the detection threshold of the first device. For example, if the first device is located in or near a patient's heart and an ultrasound signal is configured for interrogation of the first device, the ultrasound interrogation signal may be partially or completely attenuated or scattered by tissue structures such as ribs, lungs, combinations thereof, etc. Additionally or alternatively, the first device may be moving and / or rotating in space relative to its previous position and / or orientation. Conventional imaging or beamforming techniques for scanning a predetermined tissue volume and locating the first device can be time-consuming and can require high power, increased design complexity, and / or additional expertise to implement. For example, conventional ultrasound beamforming techniques including phased arrays configured to scan around the first device can be time-consuming because such techniques may use a small focal spot size of the beam (e.g., dimensions of about 1 millimeter) to scan a large area (e.g., several centimeters in all three dimensions) in search of small IMDs.

[0145] i. Wide beam question In some variations, the interrogation signal may comprise a wide ultrasound beam (e.g., a spatially unfocused beam, a plane wave, or a near-plane wave) having a wide beam diameter. In some variations, the first device may comprise an ultrasound transducer, and the diameter of the wide ultrasound beam (e.g., half-power beam diameter) at the depth of the first device within the tissue may be larger than the dimensions of the ultrasound transducer (e.g., about four times larger than the largest lateral dimension of the ultrasound transducer of the first device). As an example, in some variations, the half-power beam diameter of the interrogation signal may be about 10 cm, while the transducer of the first device may have a width of about 1 mm in each dimension. Such a design may be useful for covering a large tissue volume with the interrogation signal, thus maximizing the likelihood that the interrogation signal will be detected by the first device.

[0146] In some variations, the interrogation signal can be transmitted by the second device using a subarray including one or more ultrasonic transducer elements, as described in detail herein. In some variations, the one or more ultrasonic transducer elements may be configured for additional operations, such as receiving one or more feedback signals, transmitting power, data, commands, or other signals to the first device, receiving data, commands, or other signals from the first device, combinations thereof, etc. In some variations, it may be advantageous to design separate ultrasonic transducer elements for transmitting the interrogation signal and for transmitting power to the first device. For example, the external wireless device can include two separate transducer arrays, where one or more elements of the first array can be configured to transmit the interrogation signal and one or more elements of the second array can be used to transmit power. In some variations, the two separate arrays can include transducer elements of different dimensions and / or different materials.

[0147] One variation of an ultrasound transducer element for generating a wide beam for interrogation of a first device is described herein. The exemplary calculations presented herein use a circular disk ultrasound transducer element as an example. Similar calculations can be performed for other transducer shapes (e.g., square, rectangular cross-section, etc.). For example, formulas known in the art for other transducer shapes (e.g., having a square cross-section) can be used in place of the circular disk formula presented herein. The transducer element design presented herein can be complemented by the design of other transducer parameters, including one or more of the transducer material, thickness, spacing between elements, combinations thereof, etc.

[0148] Consider a first device comprising an ultrasonic transducer configured to receive an ultrasonic interrogation signal from an external wireless device. In some variations, the interrogation signal may have a low frequency (e.g., 100 kHz, 200 kHz, etc.) configured to enable interrogation with a wide beam diameter, since lower frequencies correspond to larger wavelengths. In some variations, the frequency of the interrogation signal may be at or near one or more resonant frequencies (e.g., open-circuit resonant frequency, short-circuit resonant frequency, harmonics of the resonant frequency, etc.) of the ultrasonic transducer of the first device. At or near such frequencies, the impedance of the ultrasonic transducer may be real or nearly real, R P In some variations, the interrogation signal frequency may be an off-resonance frequency of the ultrasonic transducer, and the impedance of the ultrasonic transducer may be a complex number. As an example, a small ultrasonic transducer (e.g., mm size) may have its R P may be designed so that the impedance may be between about 0.5 kΩ and about 500 kΩ at one or more of its resonant frequencies. In order for the first device to successfully detect the interrogation signal, the open circuit voltage (V) generated in the ultrasonic transducer of the first device due to the interrogation signal may be OC) may need to be above a predetermined detection threshold. For example, the first device may have a V of about 0.2 V (peak voltage). OC The first device may be configured to use a detection threshold of approximately 0.5 V. In some variations, such a low detection threshold may be possible if the first device includes stored energy, such as a battery, to provide energy for its operation and / or generation of the feedback signal. In some variations where the first device may not have sufficient stored energy (e.g., no battery), the first device may be configured to use a higher detection threshold (e.g., approximately 0.5 V) to overcome the threshold voltage of a typical rectifier circuit and harvest energy to generate the feedback signal. The V of the ultrasonic transducer of the first device OC is intended to serve as an example here. In some variations, the detection threshold may be set for a DC voltage produced upon rectification of the interrogation signal, the envelope of the interrogation signal, the power / energy received by the first device through the interrogation signal, the duration of the interrogation signal, data encoded in the interrogation signal (e.g., a code or unique ID), combinations thereof, etc.

[0149] The available power (P) required at the ultrasound transducer of the first device AV ) can be given by:

number

[0150] Therefore, V of 0.2V (peak voltage) OC and R in the range of approximately 500 kΩ to approximately 0.5 kΩ P About the required P AV The power of the ultrasonic transducer of the first device may be, for example, about 10 nW to about 10 μW. 2 The area of, and, as an example, η apIt can be assumed that the ultrasonic transducer of the first device can have an aperture efficiency (or acoustic-to-electrical power conversion efficiency) of about 0.5, given by: wm ) can be given by:

number

[0151] Therefore, the required I wm is approximately 0.02 μW / mm 2 ~about 20μW / mm 2 The subarray of the second device may be higher than such estimated minimum required intensity at the location of the first device. wm may be generated.

[0152] Next, consider a circular disk ultrasound transducer element (424) having a radius "a" that may be included in a second device, as shown in FIG. 4. This transducer element (424) may transmit an interrogation signal to a first device (not shown). FIG. 4 shows a schematic representation of an ultrasound beam (450) transmitted by the transducer element. The radius of this ultrasound beam (450) in the X or Y direction (e.g., the half-power beam radius or the radius where the acoustic intensity may be 3 dB lower than the intensity at the center of the beam) at a tissue depth of "d" in the Z direction may be denoted by "R." As shown in FIG. 4, the corresponding half-power beam angle θ may be given by:

number

[0153] The radius "a" can be related to the half-power beam angle "θ" by: ka sinθ=1.6 (4)

[0154] where k is the angular wave number, which is related to the wavelength (λ), frequency (f), and velocity (c) of the ultrasound in tissue by:

number

[0155] For a given selection of d, R, and f, an estimate of the required element radius can be obtained. As an example, for a tissue depth (d) of 5 cm, a beam radius (R) at this tissue depth of 7.5 cm (i.e., a beam diameter of 15 cm), and an ultrasound frequency (f) of 0.5 MHz, the radius (a) of the transducer element can be calculated to be approximately 0.92 mm (i.e., the width of the element or a diameter of approximately 1.84 mm) based on the formula: In this example, the value of k is approximately 1.92. For this element size, the half-power beam angle θ is approximately 56.3°, and the beam diameter at any tissue depth can be approximately three times the tissue depth (assuming a homogeneous tissue medium for simplicity). Therefore, for a tissue depth of approximately 20 cm, the beam diameter can be approximately 60 cm, which may be large enough for interrogation of a first device placed at this depth. As another example, if a beam radius of 7.5 cm is desired at a tissue depth of 20 cm, the above equation can be configured to estimate a transducer element radius (a) of approximately 2.18 mm (i.e., element width or diameter of approximately 4.35 mm). A homogeneous tissue medium is assumed here for simplicity. The presence of heterogeneous tissue layers and / or structures, such as ribs / lungs, can be included in more advanced calculations and / or simulations without fundamentally altering the analysis presented herein.

[0156] The transducer element contained in the external wireless device then TX The acoustic intensity at a depth d in the center of the beam (i.e., on the axis of the transducer element) is denoted by I0 and can be given by:

number

[0157] In the formula, D fdenotes the directivity function of the transducer element, which can describe the amount that the transducer element can focus an ultrasound beam compared to a uniform omnidirectional transmitter. The tissue attenuation coefficient of ultrasound in dB is a dB For example, for soft tissue, a dB The value of may be 1 dB / (cm·MHz), resulting in a total attenuation of approximately 5 dB for a tissue depth of 5 cm and a frequency of 1 MHz.

[0158] The directivity function can be written in terms of ka and can be given by:

number

[0159] where J1 is the first-order Bessel function of the first kind. For example, for the k value estimated above of about 1.92, D f The value of can be approximately 3.69.

[0160] The acoustic intensity at half-power beam radius R can be given by (I / 2). Therefore, the first device can receive an acoustic intensity of (I / 2) or greater if it is located anywhere on or within the half-power beam radius. The required acoustic intensity I, estimated above, wm To achieve the above (I0 / 2), the required P TX can be given by:

number

[0161] As an example, using the above formula and the values ​​considered in the above example, a radiation dose of 0.02 μW / mm2 is obtained within a beam radius of about 7.5 at a tissue depth of about 5 cm. 2 (R of 500kΩ p The required P at the transducer element of the external wireless device to achieve an acoustic intensity equal to or greater than the TXAs another example, for a tissue depth of about 20 cm and a beam radius of about 30 cm (for which the required transducer element size may be the same, i.e., an element radius of about 0.92 mm as above), the required P TX As another example, for a tissue depth of about 20 cm and a beam radius of about 7.5 cm, the required P TX can be about 9.2 mW.

[0162] Thus, as shown in the above example, a transducer element size (e.g., element radius a) and minimum required transmit power (P) for scanning a given region within tissue may be determined such that a feedback signal can be generated from the first device when the first device is positioned within a corresponding region within tissue, e.g., within the beam radius at a given tissue depth. TX ) can be estimated.

[0163] In some variations, a high P is used, as permitted by body safety limits. TX Configuring the second device to use approximately the maximum allowable transmit power or intensity, or a fraction thereof (e.g., half or one-fifth of the maximum allowable transmit power or intensity), for interrogation of the first device can help maximize the likelihood that the first device will detect the interrogation signal without causing any damage to body tissue. Such one or more transmit power or intensity levels of the interrogation signal can be predetermined and hard-coded into the processor of the external second device, or can be dynamically determined through real-time feedback, such as tissue temperature or tissue heating. In some variations, the interrogation signal can encode a unique identification (ID) number or a command, as described herein.

[0164] In some variations, instead of or in addition to an ultrasound interrogation signal, an RF or magnetic interrogation signal may be used, and the external wireless device and the first device's transducer may include one or more coils or antennas for transmitting and / or receiving such RF or magnetic interrogation signals. An advantage of using an RF or magnetic interrogation signal may be that the energy of the interrogation signal can be spread over a large tissue volume (due to its large wavelength). Furthermore, the RF or magnetic interrogation signal may not be significantly attenuated by the thorax or lungs. The frequency of such an RF or magnetic interrogation signal may be from about 100 kHz to about 10 GHz.

[0165] ii. Question frequency In some variations, the interrogation signal may include a first frequency, and one or more of the wireless power and the wireless data may include a second frequency different from the first frequency. In some variations, the first device (e.g., an IMD) may include at least one ultrasonic transducer including a first impedance corresponding to the first frequency and a second impedance corresponding to the second frequency. The first impedance may be greater than the second impedance. In some variations, the first device may include a first ultrasonic transducer including a first impedance corresponding to the first frequency and a second ultrasonic transducer including a second impedance corresponding to the second frequency. The first impedance may be greater than the second impedance. This may enable a high voltage to be generated in the ultrasonic transducer of the first device for a predetermined intensity of the interrogation signal. For example, for a predetermined acoustic intensity (I wm ), and the fixed area (A) and aperture efficiency (η ap ) with high R P is a large V OC (see equations (1) and (2)). This means that the first device detects a particular voltage detection threshold (e.g., minimum V OCor a DC voltage generated upon rectification of the interrogation signal).

[0166] One variation of interrogation frequency selection is described herein. The first device can include a millimeter (mm) or sub-mm sized piezoelectric element. The transducer has a short-circuit resonance (R) of approximately 2 kΩ. SC ) with a short-circuit resonant frequency of approximately 1 MHz (f SC ), and an open-circuit resonance (R OC ) with an open circuit resonant frequency (f OC As discussed herein, the first device may include a V OC The interrogation signal can be configured to have a detection threshold of approximately 1 MHz (f SC If the frequency is close to V OC The minimum P required to overcome the detection threshold AV can be about 2.5 μW (R SC Similarly, if the interrogation signal is about 1.3 MHz (f OC If the frequency is close to V OC The minimum P required to overcome the detection threshold AV can be about 0.025 μW (R SC is about 200kΩ), this is the required P AV As a result, the required strength of the interrogation signal at the first device and the required power (P TX ) can be approximately 100 times lower in this example, thereby reducing the energy consumption of the external wireless device and reducing unnecessary tissue heating. Thus, in this variation, for the first device interrogation, f OC It may be advantageous to choose a frequency close to or equal to f. The calculation above is an example of SC and f OC, and although presented at these specific values ​​of frequency and impedance, the concepts apply generally and emphasize the advantage of selecting any frequency (not necessarily a resonant frequency) at which the real part of the impedance of the transducer of the first device can be high.

[0167] In some variations, the interrogation signal may use a frequency at which the transducer of the first device can have a high impedance (for reliable detection of the interrogation signal), but the power transfer may be performed at a different frequency. This may be because the constraints for efficient power transfer may be different from the constraints for reliable detection of the interrogation signal. For example, in the example presented above, the interrogation signal may use a high V OC The advantage of generating f OC For example, wireless power transfer from an external wireless device to a first device requires frequencies close to f SC , which may be advantageous in terms of lower tissue losses and better impedance matching between the transducer impedance and the electrical load of the first device.

[0168] In some variations, the transducer of the first device may include multiple transducer elements, and not all of the transducer elements may have the same frequency or frequency range, where their impedance may be high enough to allow low-power interrogation. In such variations, the external wireless device may interrogate the first device at different frequencies (e.g., sequentially or simultaneously) to allow the first device to successfully detect the interrogation signal.

[0169] iii. High-Reliability Questions In some variations, the second device may not detect any feedback signal from the first device in response to its transmitted interrogation signal. This may be due to one or more reasons, including but not limited to, the first device being outside the beam of the interrogation signal (e.g., even if the interrogation is performed using a wide beam), the interrogation signal being partially or completely attenuated or scattered by tissue structures such as ribs, lungs, etc., the first device temporarily losing access to the interrogation signal (e.g., the IMD moving to a location behind the lungs during part of the cardiac or respiratory cycle), the first device being significantly rotated, etc.

[0170] In some variations, a system configured to exchange power or data may include a first device (e.g., an IMD) and a second device (e.g., a wireless device) comprising a processor and a transducer array. The transducer array may include multiple subarrays, where the first subarray may be configured to transmit an interrogation signal to the first device and the second subarray may be configured to receive a feedback signal from the first device. The processor may be configured to cycle through one or more of the multiple subarrays after transmitting the interrogation signal until the received feedback signal meets a predetermined condition. For example, in some variations, the predetermined condition may be comparing the strength of the received feedback signal to a threshold. In some variations, the absolute strength of the received feedback signal at one or more transducer elements may be compared to a predetermined threshold. In some variations, the relative strength of the received feedback signal between two or more transducer elements may be compared (e.g., the difference between the strengths of the received feedback signal across two or more transducer elements). The processor may be configured to cycle through one or more subarrays to transmit an interrogation signal when the feedback signal strength falls below a threshold.

[0171] As an example, the second device may include multiple transducer elements for transmitting an interrogation signal. If the feedback signal does not satisfy a predetermined condition, the external wireless device may transmit the interrogation signal through a second transducer element, and so on. For example, in some variations, the external wireless device may include a central transducer element and one or more transducer elements along its periphery. The external wireless device may first transmit the interrogation signal through the central element, and if no feedback signal is received, then transmit the interrogation signal through elements near its periphery. The external wireless device may cycle through the multiple transducer elements one by one in a predetermined order to transmit the interrogation signal until a feedback signal is received from the first device. Such cycling through the multiple transducer elements may be performed once or more than once. An advantage of cycling through the elements in a predetermined order may be a simple (low complexity) implementation of the external wireless device. An algorithm for cycling through the multiple transducer elements for interrogation of the first device may be implemented within a processor of the external wireless device (e.g., a binary search algorithm).

[0172] In some variations, the external wireless device can be configured to operate in a receive mode for a predetermined duration after transmitting the interrogation signal in anticipation of a feedback signal. For example, in some variations, such duration can be about 50 μs to about 1 ms. This duration can be determined based on the round-trip travel time of the signal between the wireless device and the first device and any waiting time that may be implemented in the first device between receiving the interrogation signal and transmitting the feedback signal. As an example, the external wireless device can cycle through multiple transducer elements one by one approximately every 1 ms until the received feedback signal meets a predetermined condition. Such a rapid interrogation scheme can be useful for quickly (e.g., within a few seconds) eliciting a feedback signal from the first device even when the first device is temporarily blocked by tissue structures such as ribs or lungs because the natural movement of the first device due to cardiac motion and breathing may be slow (e.g., on a period of about 1 second).

[0173] In some variations, the external wireless device may provide a user prompt corresponding to the status of the interrogation and whether a feedback signal from the first device was received. The user prompt may be useful for manual adjustment or repositioning of the external wireless device. As discussed above, various variations of user prompts or feedback are applicable herein. For example, if a feedback signal is not received upon transmission of an interrogation signal from one or more transducer elements, the external wireless device may notify the user via a visual and / or audio notification to move the external wireless device on the patient's chest (e.g., move it toward the left shoulder). In some variations, if a feedback signal is not received, the user may be asked to move the external wireless device to a different predetermined location on the patient's chest (e.g., while displaying a realistic or stylized image of the chest to instruct the user).

[0174] In some variations, the external wireless device may be configured to process reflections of or perform imaging of the interrogation signal, which may be reflected off one or more of the skin, ribs, lungs, combinations thereof, etc. Processing reflections of the interrogation signal or imaging may be useful for determining the next transducer element to transmit the interrogation signal from when no feedback signal is received in response to the currently transmitted interrogation signal.

[0175] In some variations, the external wireless device may determine the time window for transmitting the interrogation signal based on one or more physiological parameters that the external wireless device may be configured to measure, including, but not limited to, parameters such as heart rate, respiratory rate, blood pressure, heart sounds, combinations thereof, etc. This may be advantageous in scenarios where the first device may be temporarily shielded by tissue structures such as ribs or lungs during portions of the cardiac or respiratory cycle.

[0176] In some variations, if a feedback signal is not detected by the external wireless device in response to an interrogation signal transmitted via a first transducer element, the external wireless device may be configured to modify one or more parameters of the interrogation signal, including but not limited to, frequency, amplitude, duration, phase, time delay, combinations thereof, etc., and retransmit the interrogation signal via the same or a different transducer element.

[0177] In some variations, any subset or combination of techniques, or a combination of any subset of the above techniques, may be used. Such techniques may be applied in any order feasible until the feedback signal satisfies a predetermined condition. For example, in some variations, the external wireless device may be configured to first cycle through a plurality of transducer elements using a predetermined set of interrogation signal parameters (e.g., a fixed frequency, amplitude, duration, etc.), then optionally attempt to modify one or more parameters of the interrogation signal (e.g., frequency, amplitude, duration, etc.), then provide a prompt to the user to manually adjust the external wireless device, and optionally repeat this process until a feedback signal is detected.

[0178] iv. Feedback signal In some variations, a feedback signal may be transmitted by a first device (e.g., an IMD) in response to receiving an interrogation signal. However, reception of the feedback signal by a second device (e.g., an external wireless device, a wireless device) may be inconsistent due to one or more factors, including, but not limited to, rotation of the first device, a suboptimal radiation pattern of the first device's transducer, attenuation or scattering of the feedback signal in the link, interference between the feedback signal and a reflection of the interrogation signal received by the second device, combinations thereof, etc. Solutions provided herein may be useful in overcoming such challenges.

[0179] In some variations, the transducer of the first device may include two or more transducer elements configured to enable a collective radiation pattern with a wide acceptance angle, as described herein. If an uplink signal is simultaneously transmitted by the first device using two or more transducer elements, the resulting waves may be subject to interference that may result in partial or complete signal cancellation (e.g., null lobes). In some variations, selecting one transducer element for transmitting the uplink signal (e.g., a feedback signal) can ensure that the uplink signal propagates to the second device. In some variations, such a transducer element may be selected based on the interrogation signal power and / or voltage received by one or more transducer elements of the first device. For example, the processor of the first device processes the interrogation signals received by different transducer elements and then calculates their respective signal amplitudes, powers, and / or voltages (e.g., V OCThe processor can compare the amplitudes of the interrogation signals (or the rectified DC voltages generated from each transducer element) to determine which transducer elements receive the highest power and / or voltage, or which receive power and / or voltages higher than a predetermined threshold, as the transducer elements to be used to transmit the feedback signal. The transducer elements identified as receiving the highest power and / or voltage of the interrogation signal may include the highest link gain or the most favorable radiation pattern between the transducer elements (based on the reciprocity) for exchanging signals (e.g., power, data) with the second device. By transmitting a given power signal through the transducer element with the highest link gain, instead of distributing that given power signal among several transducer elements (some of which may not have sufficient link gain with the second device), the overall link gain and the signal-to-noise ratio (SNR) of the uplink signal at the corresponding second device can be maximized. Furthermore, the energy consumption of the first device can be minimized through selective transducer element selection, thereby extending the battery life of a battery-powered IMD. In some variations, the second device can program the first device (via downlink commands, commands encoded in an interrogation signal, etc.) to configure particular transducer elements for transmission of uplink signals (e.g., feedback signals).

[0180] In some variations, the first device may be configured to transmit an uplink signal (e.g., a feedback signal) at a power level that may be sufficient to minimize the SNR required at the second device for reliable detection and / or decoding of the uplink signal. In some variations, the first device may be configured to transmit the uplink signal at a first power (e.g., greater than required to meet the SNR requirement) that may be limited by a predetermined safety limit of the body, a predetermined voltage limit of the transmitter circuit (e.g., set by the breakdown voltage of an integrated circuit), a limit based on a predetermined energy budget of the first device, a combination thereof, etc. By transmitting the uplink signal at a higher power level, the second device may reliably receive the feedback signal or any uplink signal despite tissue-based losses, scattering due to tissue structure, relative motion and / or rotation between the first and second devices, a combination thereof, etc. In some variations, the power level transmitted by the first device for the uplink signal may be determined by the first device based on the power or voltage received by one or more of its transducer elements due to the interrogation signal. This is because such power or voltage may be a surrogate for link gain or may be used to estimate link gain. In some variations, the first device may be programmed by the second device via a downlink signal (e.g., a command) to transmit a predetermined power level of the uplink signal, which may be based on an estimation of link gain by the second device based on received feedback signals from the first device.

[0181] In some variations, the interrogation signal may reflect from tissue boundaries, ribs, lungs, and combinations thereof. The feedback signal transmitted by the first device may interfere with such reflections of the interrogation signal. Additionally or alternatively, the second device may not have precise knowledge of the location of the first device, including the separation distance between the first and second devices. Conventionally, the second device may not know the time or time window during which the feedback signal may arrive, and the second device may not be able to distinguish whether the received signal is a reflection of the interrogation signal or a feedback signal.

[0182] In some variations, interference of received signals can be reduced by configuring the first device to wait a predetermined time delay (e.g., greater than about 10 μs) between receiving the interrogation signal and transmitting the feedback signal. For example, the second device can be configured to interrogate (using ultrasound signals) the first device, which can be positioned at a tissue depth of about 20 cm or up to a maximum separation distance, and the second device may not know this separation distance in advance. If any tissue structure or tissue boundary is located within this maximum separation distance from the second device, reflections from such structure or boundary can reach the second device by a time of about 267 μs (assuming a maximum separation of about 20 cm and a speed of sound in tissue of about 1500 m / s) after its transmission of the interrogation signal. Thus, the first device can be configured to wait a time delay of at least about 267 μs between receiving the interrogation signal and transmitting the feedback signal. In some variations, the time delay can be selected based on a predetermined tissue depth at which the first device is assumed to be positioned. Such techniques may allow sufficient time for potential reflections of the interrogation signal to dissipate or die away sufficiently so as not to interfere with the feedback signal.

[0183] In some variations, the first device may include a timer (e.g., a standby timer) that includes one or more circuits or techniques, including, but not limited to, a relaxation oscillator, an RC oscillator, a ring oscillator, capacitive charging or discharging, a frequency-locked loop, combinations thereof, and the like. In some variations, the circuit may be designed for low power consumption. For example, an ultra-low-power relaxation oscillator may be configured to generate a time delay of approximately several hundred microseconds and up to several milliseconds, with an energy consumption that can be well below the stored energy of the first device (e.g., energy stored in a small battery), if necessary. In some variations, the second device may be configured to receive a feedback signal after a set time delay from the first device. In this way, the second device may be able to distinguish between tissue reflections and feedback signals.

[0184] In some variations, feedback signals and reflections from interrogation signals can be distinguished by configuring the systems described herein to differ in wireless modality (e.g., modulation) between the feedback and interrogation signals. For example, the interrogation signal may comprise an RF or magnetic signal, while the feedback signal may comprise an ultrasonic or acoustic signal, or vice versa.

[0185] In some variations, the feedback signal can be distinguished from a reflection of the interrogation signal by configuring the wireless system with different frequencies for the feedback signal and the interrogation signal. For example, the interrogation signal may be transmitted at a frequency f of the transducer of the first device. OC The feedback signal may include a frequency close to f (e.g., about 1.3 MHz as discussed herein). SC(e.g., about 1 MHz as discussed herein). As another example, in some variations, the interrogation signal may include a relatively low frequency (e.g., 100 kHz, 200 kHz, etc.) to enable interrogation with a wide beam diameter (due to the large wavelength). The power transfer (and / or transfer of the downlink signal) may be performed at a relatively high frequency (e.g., 1 MHz) to enable focusing of the beam on the first device with a beam diameter of approximately 1 millimeter for higher power transfer efficiency. Reflections of the interrogation signal may include the frequency of the interrogation signal, thereby allowing the feedback signal to be distinguished from the interrogation signal.

[0186] In some variations, the feedback signal can be distinguished from the interrogation signal based on data contained within the feedback signal. In some variations, the feedback signal can include one or more of a code, a unique ID, a unique waveform feature (e.g., data bits with a particular modulation scheme), a combination thereof, etc., that can be compared to reflections of the interrogation signal. In such variations, the processor of the second device can process the received signal to identify and distinguish the feedback signal from reflections of the interrogation signal. In some variations, signal processing techniques may include a matched filter configured to detect the presence of a code or template, or more generally, a feature that is present only in the feedback signal and not in any other signal, such as reflections of the interrogation signal. In some variations, the processor can perform this processing in real time.

[0187] In some variations, transmitting a feedback signal at a relatively high power (which may still be below safety limits) may itself be sufficient to be distinguishable from reflections of the interrogation signal, as the reflections may have relatively low power due to tissue attenuation, imperfect reflections, and scattering from tissue structures. As described herein, any subset or combination of techniques, or combinations of any subsets of the above techniques may be used together.

[0188] v. Interrogation signal detection In some variations, reliable detection of downlink signals, such as interrogation signals, downlink data, etc., by the first device may enable a wireless link to be efficiently established and maintained. In some variations, the interrogation signal may include a downlink signal, such as downlink data or commands, transmitted by the second device to one or more IMDs. In some variations, the second device may be configured to transmit the interrogation signal at a frequency at which the transducer of the first device transducer may include a relatively high impedance. The high impedance may allow a relatively large voltage to be generated at the terminals of the transducer for a given power, thereby increasing the sensitivity of the first device and enabling detection of low-power interrogation signals. For example, the interrogation signal may be transmitted at a frequency above the open-circuit resonant frequency (f) of the ultrasonic transducer of the first device. OC ) other signals, such as power and / or data signals, may include frequencies equal to the short circuit resonant frequency (f SC ), or the frequency of the guided band of the ultrasound transducer (i.e., f SC and f OC The first device may transmit the received envelope to the first device at a different frequency, such as a frequency between 1000 and 10000 (e.g., a frequency between 1000 and 10000). Additionally or alternatively, in some variations, the first device may include one or more impedance transformation networks coupled to one or more ultrasonic transducers of the first device. The impedance transformation network may transform the impedance of the ultrasonic transducer or its received voltage to a higher value. For example, the impedance transformation network may include a capacitive network. The first device may include an envelope detector circuit and a comparator circuit configured to compare the received envelope with a predetermined threshold voltage (e.g., a fixed reference voltage).

[0189] In some variations, the first device may include a first ultrasonic transducer configured to detect an interrogation signal and / or downlink data and a second ultrasonic transducer configured to receive power. The first ultrasonic transducer, the second ultrasonic transducer, or the third ultrasonic transducer may be used to transmit uplink data. For example, the first ultrasonic transducer configured to detect an interrogation signal may include a piezoelectric transducer, a capacitive micromachined ultrasonic transducer (CMUT), or the like. The first ultrasonic transducer may include a high impedance at the interrogation or downlink data frequency and / or may be coupled to an impedance transformation network to upconvert its impedance and received voltage. The second ultrasonic transducer may be independently configured for high-efficiency power recovery and / or data transmission.

[0190] In some variations, the uplink data transmission using the ultrasound transducer of the first device is performed using the frequency f of the ultrasound transducer of the first device. OC The power can be supplied by the second device to the ultrasonic transducer of the first transducer at f SC f SC Receiving power at 100 kHz can allow for efficient impedance matching between the ultrasonic transducer of the first device and the power recovery circuit, thus providing higher overall power recovery efficiency. In some variations, the first device may receive power at a frequency lower than the f of the ultrasonic transducer elements of the second device because the transducer elements may have a higher impedance at that frequency. OC The uplink data can be transmitted at Therefore, the ultrasonic transducer elements of the second device can be configured to generate a higher voltage for a given received power level of the uplink data, thereby enabling reliable detection of the uplink data.

[0191] b. Transducer configuration selection In some variations, the transducer configuration can be selected based on a received feedback signal. For example, FIGS. 3A, 3B, and 3C illustrate selecting a transducer configuration (328) based on a feedback signal (352). In some variations, the first device (e.g., an IMD) can be configured to transmit a feedback signal to the second device (e.g., a wireless device) upon receiving an interrogation signal. In some variations, the feedback signal can include one or more of an analog pulse, an acknowledgment signal, a digital energy state of the first device, a digital interrogation signal strength, an identification number, a code, a command, and one or more parameters of the first device, a wireless power signal, and a data signal. In some variations, the feedback signal can include one or more ultrasonic reflection signals and ultrasonic backscatter signals corresponding to the interrogation signal as described herein. In some variations, the first device can be configured to modulate the ultrasonic backscatter signal. In some variations, the first device can be configured to transmit the feedback signal at one or more frequencies. In some variations, the processor of the second device can be configured to identify a frequency of the transducer configuration for transmitting one or more of wireless power and downlink data to the first device based on the feedback signal. In some variations, the identified frequency of the transducer configuration may correspond to a frequency of the feedback signal at a maximum amplitude. The identified frequency can correspond to an optimal power frequency for each patient, as different patients may have different tissue depths and tissue compositions (e.g., fat content, rib structure, etc.). In some variations, the feedback signal can include transmitting one or more analog feedback signals and digital feedback signals.

[0192] In some variations, the feedback signal may include, but is not limited to, a signal acknowledging receipt of the interrogation signal, an analog feedback signal (e.g., one or more ultrasonic pulses including one or more cycles of a carrier frequency), data encoded using any modulation technique (e.g., digital modulation), combinations thereof, etc. In some variations, the first device may not explicitly transmit a different signal to acknowledge receipt of the interrogation signal; the transmission of the analog feedback signal and / or data may itself serve as an acknowledgment of receipt of the interrogation signal. In some variations, the first device may be configured to transmit such components of the feedback signal in any order. For example, the first device may be configured to first transmit digital data bits followed by an analog feedback signal, or vice versa.

[0193] In some variations, selecting one or more of the transducer configurations of the second device may include estimating a strength of a feedback signal received by a second subarray of the second device and exchanging one or more of wireless power and data signals using the one or more transducer configurations based on the estimated strength of the received feedback signal. In some variations, a processor of the second device may be configured to process the analog feedback signal to generate feedback signal data including a power and / or voltage amplitude of the feedback signal received by the transducer elements of the second device. The processor may be configured to select the transducer configuration of the second device based on a comparison of the received strength of the feedback signal with a predetermined threshold. For example, transducer elements configured to receive a feedback signal power and / or voltage amplitude above the predetermined threshold may be selected as the transducer configuration for exchanging power and / or data with the first device. The predetermined threshold may include an absolute threshold, a relative threshold, or an adjustable threshold. For example, in some variations, if the maximum feedback signal amplitude received among all transducer elements of the RTC is A0, then A0 / 3 (or

number

[0194] In some variations, selective powering of transducer elements can improve one or more of energy efficiency, tissue heating, and link efficiency. In some variations, only transducer elements comprising a selected transducer configuration can be powered on during operation (e.g., transmit, receive), while unselected transducer elements can be turned off. For example, tissue structures such as ribs, lungs, etc. can attenuate or obstruct ultrasound feedback signals received by one or more transducer elements of the second device, resulting in lower received power and / or voltage at such transducer elements compared to other transducer elements whose feedback signals are not attenuated or obstructed by such tissue structures. Based on the reciprocity, signals transmitted through the obstructed set of transducer elements can be attenuated by the tissue structures, resulting in lower received power at the first device. Furthermore, this can cause unnecessary heating at or near such tissue structures. Therefore, it may be beneficial to not transmit power through such transducer elements, thereby minimizing unnecessary tissue heating, saving energy in the second device, and achieving high overall link efficiency (e.g., link efficiency may be defined as the total power available in the first device divided by the total power transmitted by the second device). As shown in FIG. 3C, one or more transducer elements may be shielded by the ribs and / or transducer elements, resulting in the shielded transducer elements receiving lower power from the feedback signal (e.g., transducer elements that may be much farther away from the first device and therefore may experience more propagation loss through tissue compared to other transducer elements). The shielded transducer elements may not include the selected transducer configuration.

[0195] In some variations, the processor of the second device may be configured to process at least the feedback signals received by the transducer elements comprising the selected transducer configuration to generate feedback signal data including one or more parameters including the frequency, phase (and / or time delay), and amplitude of the feedback signal received by each of those transducer elements, combinations thereof, etc. Determining these parameters may be useful for determining drive signals for each of the transducer elements comprising the selected transducer configuration using techniques such as time reversal or beamforming. Time reversal may include driving a set of transducer elements with a phase or delay that may be opposite or inverted relative to the phase or delay of the feedback signal being received at the set of transducer elements.

[0196] In some variations, the frequency of the feedback signal (or any uplink signal in general) of the first device can be configured by an oscillator circuit coupled to the processor of the first device. The frequency may not be precisely known to the second device in advance. For example, the frequencies of some IMDs may be in a distribution (e.g., a Gaussian distribution with a mean of about 1 MHz and a standard deviation of about 50 kHz, or a mean of about 5%) based on effects that may be typical in integrated circuit manufacturing, such as process variations, circuit mismatches, or a combination thereof. The second device may be configured to drive corresponding transducer elements of a selected transducer configuration using a frequency (e.g., 1 MHz) different from the frequency of the feedback signal (e.g., 1.15 MHz or a frequency three standard deviations above the mean) with a phase that is inverted based on the phase of the received feedback signal. Waves generated by the transducer elements may constructively interfere at locations different from the location of the first device, resulting in suboptimal or unfocused energy focusing at the location of the first device.

[0197] In some variations, the second device may be configured to identify the frequency of the received feedback signal and may use the same frequency to power the first device, with an inverted phase or delay based on the phase or delay of the received feedback signal. In some variations, the second device may be configured to wirelessly power the first device at a frequency that is a scaled version of the frequency of the received feedback signal. For example, the frequency of the received feedback signal may be multiplied or divided by a scaling factor (e.g., an integer scaling factor). In some variations, one or more transducer configurations selected to transmit power and / or data to the first device may include a frequency different from the identified frequency.

[0198] Additionally or alternatively, the processor of the second device can generate feedback signal data for estimating the location or set of spatial coordinates of the first device within the tissue relative to the second device based on the received analog feedback signal. For example, the processor can be configured to perform triangulation based on the relative arrival times or times of flight of the feedback signals at three or more transducer elements of the second device. In some variations, the processor can be configured to process the relative arrival times of the feedback signals for two or fewer transducer elements (or two or fewer spatial coordinates) to estimate the approximate location of the first device. In some variations, the estimated location of the first device determined using triangulation can be further used to determine appropriate drive signals for the transducer elements of the selected transducer configuration. For example, estimating the location or set of spatial coordinates of the first device relative to the second device can enable the determination of a phase at which each transducer element of the selected transducer configuration can be driven for any frequency of wireless power (e.g., about 1 MHz) different from the frequency of the feedback signal (e.g., about 1.15 MHz).

[0199] In some variations, the focusing of energy in the first device may correspond to a focal spot size larger than the dimensions of one or more transducers of the first device. The focusing of energy may reduce the sensitivity of the received power due to one or more of the following: focusing inaccuracies, small relative motion or rotation of the first device, other link aberrations, combinations thereof, etc. For example, the drive signals for a selected transducer configuration (e.g., phase) may be adjusted to achieve an ultrasound focal spot diameter that may be approximately twice the width of the ultrasound transducer of the first device configured to receive wireless power.

[0200] In some variations, the processor of the second device may generate feedback signal data including the power and / or voltage amplitude of a feedback signal received by each of the transducer elements or selected transducer configurations of the second device. The feedback signal data may be generated based on the received analog feedback signal. The feedback signal data may be used to estimate link gain and determine the power transmitted through each transducer element of the selected transducer configuration to provide a predetermined received power at the first device.

[0201] In some variations, the downlink-based subarray search can compare the efficiency of downlink signal propagation paths from different subarrays of the second device to the first device. In some variations, the feedback signal can include a digital amplitude of the interrogation signal. One or more transducer configurations of the second device can select one or more of the subarrays corresponding to the largest digital amplitude of the interrogation signal. In some variations, the feedback signal can include one or more of digital first device energy data and digital interrogation strength data. In some variations, the first device can include a power source including one or more of a rechargeable battery, a capacitor, a supercapacitor, and a non-rechargeable battery. In some variations, the digital first device energy data can include power source parameters including one or more of a voltage, an energy level, a charging voltage, and a charging current. The digital interrogation strength data can include one or more digital signals representing the strength (e.g., voltage amplitude, power, etc.) of the interrogation signal received by the first device.

[0202] In some variations, the data encoded by the first unit in the feedback signal may be the power or voltage (e.g., V) received by one or more transducer elements of the first unit due to the interrogation signal (e.g., after digitizing the power or voltage or as a result of comparing the power or voltage to a predetermined threshold). OC ), the voltage of the battery and / or capacitor of the first device, the battery charging current, the DC voltage generated by the power circuitry of the first device after rectifying the interrogation signal (e.g., after DC coupling or power coupling), combinations thereof, etc. The encoded data may be used to determine the power or amplitude (e.g., voltage) of each drive signal comprising the selected transducer configuration, and / or the duration for which power may need to be transferred to the first device.

[0203] For example, data corresponding to the power or voltage received by one or more transducers of the first device due to the interrogation signal and / or the DC voltage generated by the power circuit of the first device after rectifying the interrogation signal may be directly useful in estimating link gain (e.g., the power received by the first device divided by the power transmitted by the second device). This may enable estimation of the amplitude or power and / or power duration of each drive signal comprising a selected transducer configuration to transfer a predetermined amount of power or energy to the first device. In some variations in which the power circuit of the first device comprises a rechargeable battery, parameters related to the battery (e.g., battery and / or capacitor voltage, battery charging current, etc.) may be useful in estimating the DoD of the battery and / or the power or energy required to recharge the battery to a predetermined SoC.

[0204] 5 is a block diagram of a first device (510) including a transducer (520) configured to receive a downlink signal (540), such as an interrogation signal, from a second device (not shown). The power circuit of the first device (510) may include a power recovery circuit (552), a battery charging circuit (554), a battery (556), and a supply generation circuit (558). The power recovery circuit (552) may include circuits such as a rectifier, a DC-DC converter, etc. The battery charging circuit (554) may include one or more of a constant current (CC) charging circuit, a constant voltage (CV) charging circuit, combinations thereof, etc. The battery (556) may be a rechargeable battery, such as a rechargeable lithium-ion battery, or a secondary battery. The supply generation circuit (558) may be powered from the battery (556) and may generate one or more DC supply voltages and / or currents required by the other circuit blocks. In some variations, the first device (510) may include a sensor (560), such as a pressure sensor. The processor of the first device (510) may include a sensing and processing circuit (532) and a data communication circuit (534). The sensing and processing circuit (532) may receive signals generated by the sensor (560), a voltage (V) received by a transducer, and a time domain signal (TfD).P or V OC ), battery voltage (V BAT ), battery charging current (I CHARGE ), combinations thereof, etc. The sensing and processing circuitry (532) may be configured to perform one or more of sensing, signal conditioning, digitizing, processing digital and / or analog signals, reading / writing data from / to memory (which may be included within the sensing and processing circuitry 532 or external thereto), controlling one or more circuit blocks, providing / retrieving data to / from the data communications circuitry (534), combinations thereof, etc. The data communications circuitry (534) may be configured to transmit and / or receive data to / from a second device using the transducer (520).

[0205] In some variations, the data encoded by the first device in the feedback signal can include data corresponding to the temperature of the first device. For example, the first device can include a temperature sensor configured to measure temperature data. The temperature data can be digitized. The measured temperature can be compared to a threshold value, and the result can be encoded in the feedback signal. In some variations, the second device can be configured to measure temperature (e.g., skin temperature). The temperature data can be used by the second device to adjust the voltage and / or power and / or power duration of each drive signal comprising a selected transducer configuration to maintain the temperature within safe limits.

[0206] In some variations, the feedback signal transmitted by the first device may include a broadband or ultra-wideband (UWB) signal spanning a wide range of frequencies. In some variations, the processor of the second device may be configured to process the received feedback signal (e.g., perform a fast Fourier transform, or FFT) to determine one or more frequencies for transferring power to the first device. For example, the one or more frequencies that can be used for wireless powering of the first device may correspond to a received feedback signal containing the highest power, a sufficiently high power, or a high link gain (due to reciprocity). In some of these variations, the first device may include one or more ultrasonic transducer elements with a wide inductive band (a frequency range over which the transducer impedance may be inductive), a configurable impedance matching network (e.g., comprising one or more capacitors and switches), a combination thereof, or the like, to transmit the broadband feedback signal. In some variations, the first device may be configured to transmit different ultrasonic pulses at different carrier frequencies.

[0207] In some variations, data corresponding to the power or voltage received by one or more transducers of the first device can be received from the interrogation signal. The second device can be configured to determine the orientation or rotation of the first device relative to the second device and / or monitor changes in the orientation or rotation of the first device over time based on the data. For example, the first device can include three ultrasound transducers, which can be positioned orthogonal to one another so that each ultrasound transducer can receive ultrasound signals from a direction orthogonal to the preferred direction of the other ultrasound transducers. For example, if ultrasound signals (e.g., interrogation signals) from the second device are configured to arrive at the first device from a particular direction, and there is a change in the received power or voltage at the first three ultrasound transducers over time, it can indicate the relative rotation of the first device over time. In some variations, the data can be used by the second device to estimate the rotation of the first device during a cardiac or respiratory cycle and / or over an extended period of time (e.g., over weeks, months, or years). In some variations, the data can be processed to detect motion of one or more of the heart, heart wall, heart chambers (e.g., left ventricle or LV), blood vessels, or any tissue structure in or near which the first device may be implanted. Additionally or alternatively, the data may be processed to diagnose or monitor conditions such as heart failure. In some variations, the second device can alert a user and / or a physician upon detection of the data and a user prompt is generated.

[0208] In some variations, determining the selected transducer configuration based on the feedback signal can maximize link efficiency and reliability of power transfer to the first device. In some variations, the first device can be configured to transmit a feedback signal (e.g., at least an analog feedback signal) using two or more transducer elements (e.g., all of the transducer elements of the first device). In some variations, the first device can be configured to transmit feedback signals using multiple transducer elements sequentially (e.g., after a certain delay), simultaneously (e.g., at the same frequency or different frequencies), or a combination thereof. The second device can be configured to receive the feedback signal and, based on the feedback signal, determine a selected transducer configuration having the highest overall power received by the second device. For example, after receiving an interrogation signal from the second device, the first device can be configured to transmit feedback signals one by one using each transducer element (e.g., with the same transmit power for each transducer element). A processor of the second device can calculate the overall or total power received by the second device (e.g., the sum of the power received by all of its elements) from each feedback signal. The feedback signal with the highest total received power by the secondary device may correspond to the transducer element of the primary device that has the highest link gain with the secondary device.

[0209] In some variations, the feedback signal can include an energy modality such as RF or magnetic, as discussed herein. The processor of the second device can be configured to process the received RF feedback signal (e.g., an analog feedback signal, digital data bits, etc.) in a manner similar to that described herein. For example, the processor can be configured to perform triangulation to estimate the location of the first device and determine drive signals (e.g., phase, delay, power, or amplitude of each transducer element), combinations thereof, etc. for the selected transducer configuration. Upon processing the RF feedback signal, the second device can be configured to transfer power to the first device using any energy modality, such as ultrasound, RF, magnetic, etc.

[0210] In some variations, the second device may be configured to output one or more of the following: characteristics of the interrogation signal (e.g., the transducer elements used to transmit the interrogation signal), characteristics of the received feedback signal (e.g., the amplitude of the received feedback signal at one or more transducer elements), data corresponding to the selected transducer configuration (e.g., which elements were selected for the selected transducer configuration), combinations thereof, etc. In some variations, the user may be instructed by a user prompt to take an action (e.g., manually select one or more components of the selected transducer configuration, manually adjust or move the second device, etc.). For example, a user prompt may be generated to instruct manual repositioning of the second device when the transducer elements of the selected transducer configuration are to one side of the second device. Repositioning the second device may move the transducer elements closer to the center of the transducer array of the second device.

[0211] FIG. 6 shows an example flowchart of an illustrative variation of a method described herein for interrogating a first device and transmitting wireless power. As shown, in some variations, an interrogation signal (IS) can be transmitted by a second device to the first device (602). The second device can check whether a feedback signal (FS) has been received from the first device (604). If a feedback signal is not received (or if the received feedback signal does not meet a predetermined condition), the second device can transmit an interrogation signal and configure different transducer elements (or different subarrays) to cycle through a desired set of transducer elements one or more times, as described in detail herein (606 and 608). If a feedback signal is not received by the second device, other solutions described herein may also be used.

[0212] In some variations, after the second device may try different variations of transmitting an interrogation signal (e.g., after the second device may cycle through all subarrays configured to transmit interrogation signals 606), a user prompt may be provided (610), as described in detail herein, and the user may be instructed to reposition the second device (612). These steps may then be repeated until the second device successfully receives one or more feedback signals from the first device (or until the received feedback signals meet predetermined conditions). If the second device successfully receives a feedback signal (604), a processor of the second device may generate feedback signal data (FSD) by processing the feedback signal (614), as described in detail herein. Also as discussed herein, in some variations, the second device may check whether it is sufficiently centered with respect to the first device based on the feedback signal data (616). If it is determined that the second device is not sufficiently centered with respect to the first device, a user prompt may be provided (610). The user may manually adjust or reposition the second device (612). This step may be repeated until the second device is sufficiently centered relative to the first device. In some variations, the process of centering the second device relative to the first device based on a user prompt and manual adjustment or repositioning may be skipped or bypassed, as indicated by the dashed arrow in FIG. 6. The processor of the second device may then select a transducer configuration based on the feedback signal (618) and configure the transducer configuration to transmit power to the first device (620), as discussed in detail herein.As mentioned above, FIG. 6 illustrates only an example sequence of steps, and in some variations, these steps may be performed in a different order, or other combinations or subsets of the methods described herein may be used to determine a sequence of steps, or a flowchart, for interrogating a first device and providing wireless power to the first device.

[0213] c. Interval-based exchange of wireless signals In some variations, interval-based exchange of wireless signals can be used to efficiently power and / or communicate with a first device (e.g., an IMD) that follows a spatial path within the body. In some variations, wireless signals can be exchanged between the first device (e.g., an IMD) and a second device (e.g., a wireless device) during a plurality of intervals. The method can include transmitting an interrogation signal to the first device using a first subarray of the second device; receiving a feedback signal from the first device using a second subarray of the second device; selecting one or more transducer configurations of the second device based on the feedback signal; and exchanging one or more wireless signals with the first device using the one or more transducer configurations of the second device during the plurality of intervals, wherein the wireless signals include one or more of a power signal, a data signal, an interrogation signal, a feedback signal, a downlink signal, and an uplink signal. In some variations, the method may further include transmitting a feedback signal from the first device in response to one or more wireless signals (e.g., a power signal, an interrogation signal, a data signal) received by the first device during one or more of the intervals. In some variations, the method may further include detecting one or more of: a falling edge of the one or more wireless signals; and a code corresponding to the one or more wireless signals (e.g., a power signal, an interrogation signal, a data signal) received by the first device.

[0214] In some variations, the method may include determining to transmit one or more of a power signal, an interrogation signal, a data signal, and a downlink signal to the first device in response to the received feedback signal. In some variations, the method may include determining to refrain from transmitting a wireless signal to the first device in response to the received feedback signal. For example, in some variations, if the strength of the received feedback signal is measured to be greater than a predetermined threshold, it may be determined that link efficiency between the second device and the first device is good, and the second device may decide to transmit a power signal to the first device. In some variations, if the strength of the received feedback is measured to be below a predetermined threshold, the second device may decide not to transmit any wireless signal to the first device and / or to transmit a wireless signal (e.g., an interrogation signal) after a certain waiting time.

[0215] In some variations, the transducer configuration corresponding to the subsequent interval can be selected based on one or more previously received feedback signals during one or more previous intervals. In some variations, the duration of at least one interval of the plurality of intervals can be determined by the first device. In some variations, the duration of at least one interval of the plurality of intervals can be determined by the second device. In some variations, the first device can be configured to periodically transmit a feedback signal during one or more of the intervals.

[0216] As an example of an interval-based powering example, a variation of interval-based powering is described herein, where a power signal may be transmitted by a second device to a first device during multiple power intervals. However, it will be understood that such a method may generally be applied to any type of wireless signal exchange between a first device and a second device during multiple intervals.

[0217] In some variations, interval-based power transfer can efficiently power a first device that follows a spatial path within the body. For example, a small (e.g., millimeter-sized) IMD implanted in the heart may move / rotate due to heart wall movement and / or breathing. A transducer configuration can be selected to transmit wireless power to the first device at predetermined intervals configured for efficient power transfer.

[0218] In some variations, the interval-based powering method may include transferring power to the first device at different time intervals (referred to as power intervals). The transducer configuration may be determined separately for each power interval, as described above. Examples are presented herein for powering a moving IMD implanted in or near the heart or a heart chamber.

[0219] In some variations, the second device may be configured to transmit an interrogation signal to the first device, receive a first feedback signal from the first device, process the first feedback signal to generate first feedback signal data, and determine a first selected transducer configuration based on at least the first feedback signal data. The second device may configure the first selected transducer configuration to transfer power to the first device during a first power interval. At the end of the first power interval, the first device may be configured to transmit a second feedback signal to the second device. The second device may process the second feedback signal to generate second feedback signal data and determine a second selected transducer configuration based on at least the second feedback signal data. The process of transmitting a feedback signal after a power interval to determine a selected transducer configuration for the next power interval may be repeated until one or more predetermined conditions are met (e.g., a sufficient amount of power or energy is transferred to the first device). Different variations of the feedback signal, feedback signal data, and selected transducer configuration as described herein are applicable herein.

[0220] In some variations, the second feedback signal transmitted by the first device at the end of the first power interval may encode data corresponding to the power signal received by the first device during the first power interval. The second feedback signal may encode data in a manner similar to encoding data in an interrogation signal as described herein. For example, in some variations, the second feedback signal may include, but is not limited to, a signal acknowledging receipt of power during the first power interval, an analog feedback signal, data corresponding to the power or voltage received by one or more transducer elements of the first device during and / or at the end of the first power interval (e.g., after digitizing the power or voltage or as a result of comparing the power or voltage to a predetermined threshold), the battery voltage of the first device during and / or at the end of the first power interval, the battery charging current during and / or at the end of the first power interval, the DC voltage generated by the power circuitry of the first device during and / or at the end of the first power interval, combinations thereof, etc.

[0221] In some variations, the duration of a single power interval may be predetermined or determined in real time during wireless powering of the first device. In some variations, the duration of a power interval may be determined by the first device and / or the second device. For example, the predetermined duration may be based on prior knowledge of the movement or velocity of the first device and the effects or factors that cause such movement. For example, a small first device (e.g., an IMD) attached to the heart wall may move periodically with a period of about 1 second over a heart rate of about 60 beats per minute (ignoring the effects of breathing for simplicity). As an example, assuming the first device traverses a total path length (round trip) of about 10 cm in one cycle and assuming the velocity of the first device may be constant over time, it can be estimated that the first device may move about 1 mm within a duration of about 10 ms. If the ultrasound transducer of the first device has a width of approximately 1 mm and the power beam has a half-power beam diameter of approximately 4 mm, the duration of the power interval can be set to approximately 10 ms, after which a new transducer configuration can be determined to reliably power the first device in its new position. In some variations, the movement, path, or trajectory of the first device can be mapped using any technique, such as imaging or triangulation based on analog feedback signals. The spatial path can be used to determine the duration of the power interval. In some variations, the duration of the power interval can be approximately 1 ms to approximately 100 ms. In some variations, the set of power intervals for powering the first device can have the same duration or different durations. In some variations, the set of power interval durations can be determined based on knowledge of the movement of the first device. For example, if it is known or determined that the first device is likely to not move significantly during a large time window (e.g., approximately 300 ms) within the cardiac cycle (e.g., diastole), the second device can estimate such time window of the cardiac cycle (e.g., by measuring heart rate or ECG) and use a longer duration of the power interval (e.g., approximately 300 ms) during that time window.

[0222] In some variations, the first device can be configured to transmit a feedback signal at the end of a power interval (e.g., in addition to being configured to transmit a feedback signal after receiving an interrogation signal). This variation is illustrated in FIG. 7A, where different signals at the first device (e.g., an IMD) are conceptually represented on a timing diagram. Note that there may be a finite, non-zero time delay between the different signals and / or the amplitude and / or duration of the signals may differ from those conceptually illustrated in the diagram. In some variations, the first device can be configured to detect a falling edge of a voltage envelope received by one or more transducer elements of the first device, or a drop in its received power or voltage generally below a predetermined threshold. A falling edge or drop in the first device's received power or voltage may be due to the second device ending a power interval, or a significant change in the position or orientation of the first device while the second device is still transmitting power within the power center, or both. In some variations, the first device may be configured to detect a code in one or more wireless signals (e.g., an interrogation signal, a power signal, a data signal) transmitted by the second device.

[0223] In some variations, as shown in FIG. 7B, the second device can transmit an interrogation signal after a power interval. The first device can respond to the interrogation signal by transmitting a feedback signal that can be received and processed by the second device to determine the selected transducer configuration for the next power interval. In some variations, the second device can be configured to transmit a specific downlink code or command to the first device during and / or at the end of a power interval. As conceptually shown in FIG. 7C, the command can specifically trigger the first device to transmit a feedback signal, and the first device can transmit the feedback signal upon detection of the code or command.

[0224] In some variations, the second device can stop transmitting wireless power to the first device based on the feedback signal data. For example, the feedback signal from the first device can encode the voltage of the battery of the first device, and the processor of the second device can decode the encoded voltage. The processor can determine the SoC of the battery of the first device and stop wireless power transfer to the first device if a desired or maximum SoC has been reached. In some variations, the first device can send a command to the second device to stop transmitting wireless power when a certain condition is met (e.g., when the battery of the first device has reached a desired or maximum SoC).

[0225] In some variations, the second device may generate user prompts (e.g., user feedback) at any or all points during the performance of one or more methods described herein. The user prompts may include, but are not limited to, the SoC of the first device, the SoC of the second device, whether charging of the first device is complete, whether charging of the first device has been interrupted for any reason, combinations thereof, etc. Interruptions in charging or wireless powering of the first device may be due to reasons including, but not limited to, the user moving or removing the second device from the patient's body, the second device being dropped or becoming dislodged or disconnected, the second device's battery being low, combinations thereof, etc. In response to the user prompt, the user may take actions such as recharging the second device's battery if the second device's battery is low, repositioning the second device if the second device is dislodged, turning off and removing the second device if charging of the IMD is complete, combinations thereof, etc.

[0226] In some variations, the second device can be configured to store data corresponding to the movement of the first device and / or a selected transducer configuration corresponding to the location of the first device in the memory of the second device and use the data for one or more subsequent power intervals. The data may include one or more of the following: the position of the first device (e.g., one or more spatial coordinates and / or orientation or rotation of the first device, the position of the first device as a function of time), parameters of the selected transducer configuration (e.g., selection of transducer elements, drive signals for transducer elements, etc.), temporal parameters related to the movement of the first device (e.g., heart rate, respiratory rate, etc.), the velocity and / or acceleration of the first device relative to the second device, combinations thereof, etc. For example, in some variations, the spatial coordinates of the first device as a function of time over one or more cardiac / respiratory cycles or the selected transducer configuration can be stored in the memory of the second device. The spatial coordinates can be used by the second device to reliably power the first device in one or more subsequent cardiac / respiratory cycles. In some of these variations, the second device may not need to determine a new selected transducer configuration in real time for every power interval (which may help save computational time and energy), and may rely on a previously determined selected transducer configuration to reliably power the first device. In some variations, the selected transducer configuration may produce a focal spot size at the first device that may be larger than the dimensions of one or more transducers of the first device (e.g., the focal spot diameter may be four times the diameter of the transducers of the first device). This may reduce the sensitivity of the received power of the first device to one or more of small deviations from its trajectory, other link aberrations, combinations thereof, etc., for which the selected transducer configuration may be stored in the memory of the second device.

[0227] i. Intermittent wireless signal exchange In some variations, the first device may temporarily move or rotate, such that the link gain between the second device (e.g., an external wireless device, a wireless device) and the first device may be reduced over a portion of the first device's spatial path (e.g., trajectory). For example, during certain heartbeats (or due to breathing), a first device attached to the heart wall may temporarily move to a position behind the lungs or ribs, such that the ultrasound beam from the second device to the first device may be partially or completely blocked or attenuated. Exchanging wireless signals (e.g., power, data, or other signals) with the first device during such times may be inefficient. For example, low link gain may require high transmit power from the second device, resulting in unnecessary tissue heating. The solutions provided herein may be useful in overcoming such challenges.

[0228] In some variations, methods of intermittently exchanging wireless signals, as described herein, may be used. In some variations, the second device may be configured to inhibit transfer of wireless signals (e.g., power, data, interrogation signals) to the first device in response to a feedback signal during a method of interval-based exchange of wireless signals. Examples of intermittent power supply are described herein, where the second device may be configured to inhibit power supply to the first device during one or more intervals. However, it will be understood that such methods may generally be applied to the exchange of any type of wireless signal between a first device and a second device during multiple intervals.

[0229] In some variations, a significantly lower received power and / or voltage of the analog feedback signal compared to a previously received feedback signal (e.g., 6 dB lower power compared to the power of the previously received feedback signal) may correspond to a movement and / or rotation of the first device to an unfavorable position / configuration where link gain is significantly lower. In some of these variations, powering the first device at a different time when link gain is more favorable may be preferable to transmitting greater power from the second device to compensate for the lower link gain. In some variations, the second device may be configured to make a determination not to transfer wireless power based on processing one or more of the analog feedback signal, a feedback signal including digital data bits encoding the power or voltage received by one or more transducer elements of the first device during and / or at the end of the first power interval, a DC voltage generated by the power circuitry of the first device during and / or at the end of the first power interval, a combination thereof, etc.

[0230] In some variations, one or more components of the feedback signal data (e.g., power received by transducer elements of the first device) can be compared to corresponding components of feedback signal data previously generated during interval-based powering, or one or more components of the feedback signal data can be compared to one or more predetermined (e.g., absolute) thresholds to determine whether to transfer wireless power within the next power interval. This method may be referred to as intermittent powering. Intermittent powering can use energy efficiently, extend battery life of the second device, and avoid unnecessary heating of tissue.

[0231] In some variations, the second device may determine not to transfer power to the first device during a particular power interval and then determine how and when wireless powering of the first device may be resumed. In some variations, in response to the determination not to transfer power, the second device may wait a predetermined time delay before transmitting one or more interrogation signals to the first device. In response to receipt of this interrogation signal by the first device and receipt of a corresponding feedback signal by the second device, the second device may resume power transfer to the first device (e.g., resume interval-based powering), as described above. As shown in FIG. 8, the second device may be configured to transmit the interrogation signal after a time delay (e.g., a wait time) of about 1 ms to about 500 ms. For example, in some variations, the wait time may be about 100 ms, which may be sufficient for the first device to move / rotate back to a position / orientation where link gain with the second device is favorable or likely to be sufficiently high. In some variations, the second device may continue to transmit interrogation signals to the first device (e.g., periodically every 10 ms or every 100 ms, etc.) until it receives a feedback signal from the first device indicating a favorable link gain.

[0232] In some variations, the second device may decide not to transfer power to the first device. The first device may then be configured to transmit one or more feedback signals to the second device after waiting a predetermined time delay (e.g., periodically every 10 ms or every 100 ms, etc.) without being explicitly asked by the second device. In some of these variations, the second device may wait to receive a feedback signal from the first device. In some of these variations, the first device may use stored energy (e.g., from a battery) to transmit the one or more feedback signals. In some variations, the first device may be configured to transmit the one or more feedback signals until one or more of the following conditions are met: the first device receives power from the second device in the next power interval; the second device sends a command to the first device to stop transmitting feedback signals; the first device transmits a predetermined number of feedback signals or for a predetermined duration; combinations thereof; etc.

[0233] d. Transducer configuration based on reflected signals In some variations, the feedback signal may include an active uplink signal transmitted by a first device, such as the first device, (e.g., upon detection of an interrogation signal). The active uplink signal may provide several advantages, such as a large received signal or signal-to-noise ratio at the second device, flexibility in selecting the frequency of the uplink signal, and duration for the interrogation signal. However, in some applications, detecting the interrogation signal may require a wake-up receiver capable of detecting low interrogation signal levels. In some variations, the wake-up receiver may consume a large amount of energy. Therefore, a first device including a wake-up receiver may require a larger battery.

[0234] In some variations, ultrasound imaging can be used to localize the first device. For example, ultrasound imaging can include beamforming to sweep or scan a focused beam across a region or volume of tissue. However, ultrasound imaging may require a relatively long time to scan a large tissue region (e.g., several centimeters in all three dimensions) using a small focal spot size (e.g., 1 millimeter diameter), complex processing power, and / or high power consumption of the second device.

[0235] In some variations, the subarray of the second device can be configured to transmit an ultrasound interrogation signal to the tissue. The corresponding feedback signal can include one or more ultrasound reflection signals from one or more first devices. The received reflection signals can be processed by a processor of the second device to generate feedback signal data and identify which portions or features of the reflection signals may correspond to the first device. This can be used to determine a transducer configuration using time reversal or other search / beamforming techniques. The transducer configuration can be used to focus on the location of the first device for transmitting power, data, and / or other signals to the first device and / or receiving data and / or other signals from the first device.

[0236] In some variations, the subarray that can be configured to transmit the interrogation signal can include one or more ultrasound transducer elements of the second device. The second device can be configured to generate a spatially wide or unfocused beam (e.g., a plane wave, near-plane wave) within the tissue, referred to as low-gain transmission. For example, the half-power beam diameter of the interrogation signal near the first device can be greater than approximately twice the maximum lateral dimension of the transducer of the first device receiving the interrogation signal. An unfocused beam can enable rapid scanning of a large tissue volume to locate the first device. In some variations, the transducer elements or subarrays of the second device can be cycled (e.g., configured one by one as a subarray) to scan the tissue until a transducer configuration is determined according to predetermined criteria. In some variations, one or more transducer elements can be configured to transmit the interrogation signal with a relatively focused beam (e.g., high-gain transmission) to reduce transmit power requirements. In some variations, the interrogation may be performed using a full beamforming scan (e.g., adjusting the phase of one or more transducer elements of a subarray to scan the beam at various angles).

[0237] In some variations, the ultrasonic interrogation signal includes a short pulse width (e.g., a few microseconds to tens of microseconds) that allows sufficient resolution (e.g., on the order of millimeters to centimeters) to distinguish between different structures, such as the first device, ribs, lungs, etc., based on the reflection of the interrogation signal. A short pulse width corresponds to a wide bandwidth, requiring wideband transducer elements and potentially resulting in a large minimum detectable signal (MDS) requirement for the reflected signal received by the second device (due to the blending of noise across the wide bandwidth). Thus, in some variations, an ultrasonic interrogation signal with a longer pulse width (e.g., on the order of hundreds of microseconds, milliseconds, or more) can be used to relax the bandwidth requirement (e.g., allowing the use of transducer elements with lower bandwidths). In some variations, the end or falling transition of the pulse of the reflected signal can be processed to determine the transducer configuration.

[0238] In some variations, the carrier frequency of the interrogation signal may be the same as the power or data transfer frequency, which may enable accurate modeling of the link and determination of transducer configurations for efficient power or data transfer. In some variations, different carrier frequencies may be used for the interrogation. For example, in some variations, a higher carrier frequency may be used to transmit shorter pulses to achieve higher resolution in identifying the first device. In some variations, a lower carrier frequency may be used to reduce propagation loss of the interrogation signal through tissue, thereby increasing the strength of the reflected signal from the first device and / or reducing the transmit power requirements. The transmit power required for this method may be estimated based on the MDS of one or more transducer elements of the second device, tissue-based losses, the radar cross section of the first device, and a radar range equation. In some variations, the carrier frequency of the interrogation signal may be selected to increase the strength of the reflected signal from the first device (e.g., from the transducer of the first device) and / or result in uniquely identifiable different frequency components in the reflected signal from the first device due to nonlinear backscattering.

[0239] In some variations, the interrogation signal transmitted into the tissue by the subarray of the second device can generate one or more feedback signals including one or more reflected signals. The reflected signals can include reflections from one or more first devices and / or one or more tissue structures such as ribs, lungs, boundaries between two types of tissue, combinations thereof, etc. In some variations, a time window or time delay based on the propagation speed of ultrasound in tissue can be used to record reflected signals from a desired tissue depth, or a set or range of tissue depths. In some variations, three or more transducer elements of the second device can be used to triangulate the location of the first device based on processing of the feedback signals.

[0240] In some variations, the second device may include one array of transducer elements, from which transducer elements including the TTC and the RTC may be selected for a given iteration of the methods described herein. In some variations, a first subset of the array may be configured for transmission only, and one or more transducer elements including the TTC may be selected from the first subset. In some variations, a second subset of the array may be configured for reception only, and one or more transducer elements including the RTC may be selected from the second subset. In some variations, the second device may comprise two arrays. A given array may be configured to either transmit or receive signals. In some of these variations, the transducer elements including the TTC may be separate (e.g., distinct) from the transducer elements including the RTC.

[0241] In some variations, the feedback signal, including the reflected signal, can be processed by a processor of the second device to generate feedback signal data to estimate the shape and / or size of the reflector. The feedback signal can further be used to identify which portions of the reflected signal may correspond to the first device as opposed to tissue structures such as ribs, lungs, etc. The processing can be performed in one or more manners. For example, if the interrogation signal is in the form of ultrasound pulses, the reflected signal received by one or more transducer elements of the second device can include one or more ultrasound pulses. Waveform characteristics of the received reflected signal, such as the number of pulses, amplitude, phase, delay, and / or frequency of the one or more pulses, and / or variation of the waveform characteristics across different transducer elements of the second device, can depend on the position, shape, size, and / or characteristics of the reflector.

[0242] In some variations, the amplitude, phase, and / or delay characteristics of the reflected signal and / or one or more pulses within the reflected signal can be compared across one or more transducer elements of the second device to distinguish between different reflection sources. Reflections from the first device may originate from a single small spot in the tissue, while reflections from the ribs may originate from multiple spots (or a periodic grating), and reflections from the lungs may originate from a large surface area. In some variations, knowledge of the approximate tissue depth or range of tissue depths of the first device can be used to identify which portions of the reflected signal correspond to the first device. For example, the ribs may be located at a shallow tissue depth (e.g., less than about 2 cm) and the first device may be located at a deeper tissue depth (e.g., greater than about 2 cm), so that the reflection from the ribs arrives at the second device earlier than the reflection from the first device. In some variations, it may be known that the nth reflection event (n is an integer) or the nth pulse of a received reflected signal containing multiple pulses is from the first device. For example, the fourth reflection or fourth pulse of the received reflected signal may be known to correspond to the first device, while the first, second, and third reflections may be known to correspond to reflections from skin, ribs, and / or other structures. In some variations, the processor of the second device may be configured to process the reflected signal to detect additional frequencies (separate from the frequency of the interrogation signal) to identify which portions of the reflected signal or which pulses of the reflected signal correspond to reflections from the first device. For example, an interrogation signal incident on the first device may experience nonlinear backscattering, resulting in different frequency components in its reflections. The nonlinear backscattering may be a useful signature of the received reflected signal for identifying the first device.

[0243] Identification of the portion of the received reflected signal corresponding to the first device can be used to determine a transducer configuration for efficiently exchanging (e.g., transmitting, receiving) wireless signals with the first device. In some variations, certain transducer elements of the second device that receive significantly lower reflected signal amplitudes from the first device compared to other transducer elements may not be used as part of a transducer configuration for transmitting power to the first device. For example, the path from the transducer element to the first device may be blocked by a rib. In some variations, the relative time delay and / or amplitude of the reflected signal of the first device received at one or more transducer elements of the second device may be reversed while transmitting power. This may focus the transmit beam on the location of the first device. In some variations, the relative time delay of the reflected signal of the first device at three or more transducer elements of the second device may be used to estimate the relative position or range or location of the first device within the tissue (e.g., using triangulation). In some variations, after estimating the approximate location of the first device within the tissue, a transducer configuration can be determined to include a subarray power / data snapshot. For example, the subarray power snapshot can refer to a selected set (e.g., subarray) of transducer elements of the second device, along with their drive signals (e.g., amplitude, frequency, phase), configured to selectively focus power at the location of the first device. In some variations, after estimating the approximate location of the first device within the tissue, phased array beamforming using a subset of the transducer elements of the second device or all of the transducer elements of the second device can be used to focus on the location of the first device for efficient exchange of wireless signals.

[0244] In some variations, the downlink-based search for transducer configurations can be performed using a feedback signal including one or more ultrasound reflection signals from one or more first devices or tissues. For example, the subarray can include a subarray configured to transmit an interrogation signal to the tissue, and the second device can be configured to receive and process the reflection signals from the tissue and / or the first device to identify the approximate location of the first device. The second device can perform an A-scan (amplitude scan) or a B-scan (brightness mode scan), etc., to identify reflections from the first device and estimate its location within the tissue. This process can be repeated for a predetermined number of different subarrays to search for a transducer configuration with the highest ultrasound link gain with the first device. For example, a larger amplitude or echo in an A-scan corresponding to a given subarray can indicate that the subarray has a higher ultrasound link gain with the first device and can be designated as the selected transducer configuration.

[0245] In some variations, the steps described herein may be repeated periodically to track a first device that moves relative to a second device due to breathing, heartbeat, etc. For example, in some variations, the method may be applied to interval-based power and data transfer. The transducer configuration may be periodically determined or updated to exchange wireless signals with a moving first device during a time interval. In some variations, the interrogation signal may be changed over subsequent intervals during interval-based power and data transfer. For example, one or more different transducer elements may be configured as sub-arrays to transmit interrogation signals at different intervals. In some variations, the interrogation signal may not be transmitted over every interval; instead, reflections of a power signal transmitted by a transducer configuration of a previous interval may be processed to determine the transducer configuration for the next interval.

[0246] In some variations, the received reflected signals may be processed to identify which portions of the reflected signals correspond to multiple first devices, and one or more transducer configurations may be determined for efficiently exchanging wireless signals with multiple first devices simultaneously or at different times.

[0247] An interrogation signal in the form of a short pulse spanning a wide frequency band may be subject to dispersion in tissue, causing the reflected feedback signal to have one or more pulses that are smoothed (i.e., have gradual rise / fall transients). This may be due to the frequency dependence of the subarray gain (e.g., limited bandwidth), the radar cross section of the first device, and / or link dispersion. While short pulses may provide high axial resolution, the dispersion may make it difficult to identify the portion of the reflected signal that corresponds to the first device, estimate the location of the first device within the tissue, and / or determine the transducer configuration using time-reversal or other search / beamforming techniques.

[0248] In some variations, the feedback signal data can include the relative phase, amplitude, and / or time delay—i.e., the differences in these waveform features of the received reflected signal across the transducer elements of the second device. This can be useful when feedback signals received by different transducer elements may be subject to similar levels of dispersion. For example, the relative time delay between smoothed pulses (corresponding to reflections from the first device) received by the transducer elements of the second device can be accurately determined by using a rising / falling edge detector circuit (e.g., comprising an envelope detector and a comparator or Schmitt trigger) and calculating the time difference between the output pulses of the edge detector circuit. In some variations, the relative time delay can be used to determine the transducer configuration for efficiently powering the first device based on time reversal. In some variations, to address dispersion, an interrogation signal with a long pulse width (e.g., hundreds of microseconds, milliseconds, etc.) or low bandwidth can be used. However, this can result in reduced axial resolution, making it difficult in some applications to distinguish the reflected signal coming from the first device from signals of tissue structures such as ribs, lungs, etc.

[0249] In some variations, the second device can be configured to receive the feedback signal during one or more time windows or after a predetermined time delay to capture the last few cycles or falling edges of the long received pulses corresponding to reflections from the first device. For example, in the case of a first device implanted in / near the heart, configuring the second device to receive the feedback signal after a predetermined time delay can allow reflections from shallow tissue structures, such as ribs or skin, to be ignored and only the reflected signals from the first device and any deeper tissue structures to be processed to generate feedback signal data. In some variations, the second device can be configured to receive or record all reflections and can use analog and / or digital post-processing to identify the last few cycles or falling edges of the long pulses corresponding to reflections from the first device. The relative time delays of the last few cycles or falling edges across different transducer elements can be used to determine a transducer configuration for efficient wireless power / data exchange with the first device.

[0250] In some variations, the interrogation signal can include a range of frequencies (e.g., a chirp signal). In some variations of the ultrasound interrogation signal, the range of frequencies can include frequencies (e.g., a range centered around) at which the size of the first device and / or components of the first device (e.g., one or more ultrasound transducers of the first device) can be on the order of a wavelength (or a multiple of a wavelength). The radar cross section (RCS) of the first device and / or components of the first device (e.g., ultrasound transducers) can vary significantly across frequency due to resonance effects (e.g., the RCS can have a local maximum within this frequency range, can have a local minimum, can oscillate at this frequency, etc.). This phenomenon can result in a unique signature of a mm-sized first device in the received feedback signal, which can be useful for distinguishing the first device from larger cm-sized tissue structures such as ribs, lungs, etc.

[0251] e. Transducer configuration based on backscattered signals In some variations, the feedback signal from the first device (e.g., an IMD) may include a backscatter signal, such as an ultrasonic backscatter signal. In some variations, the first device may be in a first mode, such as a sensing mode, before the second device (e.g., an external wireless device) transmits an interrogation signal to the first device. In some variations, the second device may transmit a first interrogation signal to the first device, and upon receiving this, the first device may configure itself into a second mode, which may be useful for determining a transducer configuration for efficient wireless power / data exchange with the first device. In variations of the methods described herein, such a second mode may be a backscatter mode. The first device may be configured to backscatter the incoming interrogation signal, as described in detail herein. In some variations, energy stored in the first device (e.g., a battery or capacitor) may be useful for configuring the first device for backscattering (e.g., to modulate a load circuit described herein). The second device transmits a second interrogation signal that can be received by the first device in the second mode, and a corresponding feedback signal from the first device (e.g., a backscattered signal from the first device corresponding to the second interrogation signal) can be used to determine the transducer configuration. In some variations, the second mode may not be required, and the first device can always be configured to backscatter the incoming interrogation signal.

[0252] In some variations, the first device may include one or more ultrasonic transducers coupled to one or more circuits that can be used to affect or modulate ultrasonic backscatter signals from the first device in response to one or more interrogation signals transmitted by the second device. In general, affecting or modulating the backscatter signals from the first device may result in a unique signature of the first device in the feedback signal and / or may improve the signal-to-noise ratio (SNR) of the feedback signal coming from the first device. This may be useful for reliably locating the first device.

[0253] In some variations, the circuitry coupled to the ultrasonic transducer may include one or more of a load circuit, a rectifier or power recovery circuit, combinations thereof, etc. In some variations, the circuitry may be configured to modulate the amplitude, phase, and / or one or more frequency components of the backscattered signal (e.g., add new frequency components to the backscattered signal relative to the interrogation signal).

[0254] In some variations, the load circuit coupled to the ultrasonic transducer of the first device may include one or more of a short, an open, one or more switches, one or more resistors, one or more resistive impedances (e.g., capacitors), one or more modulating impedances, combinations thereof, etc. For example, shorting or connecting a small impedance across the terminals of the ultrasonic transducer may increase the amplitude of the backscattered signal, allowing the processor of the second device to reliably detect the first device. In some variations, instead of a short, a predetermined impedance may be coupled across the ultrasonic transducer. This may be useful for measuring the strength of the interrogation signal received by the first device (e.g., the voltage or power received by the ultrasonic transducer) and / or for recovering some power from the interrogation signal while still increasing the amplitude of the backscattered signal from the first device.

[0255] In some variations, the load circuit may include a modulated impedance, which may include any impedance that may be modulated or change as a function of time. Changes in the modulated impedance may result in modulation of a backscatter signal (which may be referred to as a modulated backscatter signal) that can be detected by a processor of the second device and used to locate the first device. Modulation of the backscatter signal may include changes in one or more of amplitude, frequency, and / or phase relative to the incoming interrogation signal, and / or variations in one or more of amplitude, frequency, and / or phase as a function of time. For example, in some variations, the processor of the first device may switch the impedance seen by the ultrasound transducer between two or more values ​​(e.g., between an open circuit and a short circuit), periodically or at one or more modulation frequencies. This may result in a modulated backscatter signal having frequency components or tones equal to the modulation frequency and / or its harmonics, which may be detected by a processor of the second device to locate the first device and / or determine a transducer configuration for efficiently powering the first device.

[0256] In some variations, the modulation frequency may be approximately equal to the frequency used to power the first device or transmit downlink data to the first device. This may be useful for time reversal because it may allow the time delay or phase of the received feedback signal to be measured at the powering frequency. For example, if the desired powering frequency in the ultrasonic link is approximately 1 MHz, the interrogation signal may be transmitted at a higher frequency (e.g., approximately 2 MHz) and the backscattered signal may be modulated at a modulation frequency of approximately 1 MHz. The processor of the second device may measure the time delay or phase of the components of the feedback signal at approximately 1 MHz and use those time delays or phases for time reversal to effectively power the first device at approximately 1 MHz.

[0257] In some variations, the modulation frequency may be different from the frequency used to transmit power or data to the first device. For example, in some variations, the modulation frequency may be a low frequency (e.g., about 100 kHz) that experiences low propagation losses through tissue, thereby enabling reliable detection of the modulated backscattered signal by the second device. In some variations, the modulation frequency may be a multiple of the feed frequency, or vice versa. In some variations, the processor of the second device may process the time delay or phase of the received feedback signal at the modulation frequency. The processor may further use time reversal to determine the time delay or phase required to transmit power to the first device at the feed frequency.

[0258] In some variations, the load circuit may be modulated to encode digital data that may enable the second device to uniquely identify and / or locate the first device. The digital data may include one or more of an ID code, a command, a code acknowledging receipt of an interrogation signal by the first device, a code representing a digitized energy state of the first device (e.g., its battery voltage), combinations thereof, etc.

[0259] In some variations, the load circuit can be modulated to generate one or more nulls or notches in the backscatter signal from the first device. The nulls or notches can include portions of the feedback signal received by the second device where the amplitude of the feedback signal is low or near zero. In some variations, the nulls or notches in the backscatter signal can be generated by switching the load circuit impedance between an open circuit and a short circuit. The processor of the second device can be configured to detect the nulls or notches in the received feedback signal to uniquely identify and / or locate the first device. For example, the second device can measure the relative time delay of the notches on different transducer elements and process the time delay to determine the transducer configuration using time reversal, triangulation, or the like.

[0260] In some variations, a rectifier circuit or power recovery circuit coupled to the ultrasonic transducer can result in a backscattered signal having a harmonic (e.g., the third harmonic) of the interrogation signal frequency due to the nonlinear impedance (e.g., a diode) of the rectifier or power recovery circuit. The additional frequency component may be present only in the backscattered signal coming from the first device, as opposed to other reflections of the interrogation signal, and may be used by a processor of the second device to locate the first device.

[0261] In some variations, the downlink-based search for a transducer configuration can be performed using a feedback signal including one or more backscattered signals. For example, a subarray can be configured to transmit an interrogation signal to the tissue, and a second device can be configured to receive and process the backscattered signal from the first device. This process can be repeated for multiple different subarrays to search for the optimal subarray with the highest ultrasonic link gain with the first device. For example, for a given subarray, envelope detection of the received feedback signal can be used to detect the modulated backscattered signal. The detected signal can indicate that the subarray has sufficient ultrasonic link gain with the first device. Furthermore, the subarray can be selected as the transducer configuration for efficiently exchanging power / data with the first device.

[0262] f. Array configuration of the second device The systems and methods described herein are configured to exchange wireless signals between a first device (e.g., an IMD) and a second device (e.g., a wireless device). In applications such as ultrasound imaging, it may be common to use a single transducer array including one or more transducer elements configured to both transmit and receive signals. However, the second device may comprise two or more separate arrays, each including one or more transducer elements. One or more arrays may be configured to transmit signals (transmit arrays), and one or more arrays may be configured to receive signals (receive arrays). For example, in some variations, the second device may comprise one or more transmit arrays, one or more receive arrays, and one or more arrays that may be configured to both transmit and receive signals. The array configurations described herein may eliminate or reduce the use of transmit and receive switches typically used to configure transducer elements for both transmitting and receiving signals to reduce design complexity and / or power loss of the second device. The array configuration also allows for design flexibility by decoupling design constraints on the transducer elements and electronics for implementing the transmit and receive functions. In some variations, the transducer elements of the transmit and receive arrays may be the same or different types, shapes, materials, dimensions, etc. For systems with separate transmit and receive arrays, it may be difficult to determine the transducer configuration for transmitting downlink signals (power, data, etc.) to the first device. For example, a feedback signal received on the receive array includes transducer elements that are not configured to transmit wireless signals to the first device.

[0263] In general, the geometric relationship between the elements of the transmit array and the elements of the receive array can be used by the processor of the second device to determine drive signals for the transmit array elements based on received feedback signals on the receive array elements. In some variations, the transmit array and the receive array may be partially or completely interleaved or interspersed with each other. For example, the transducer elements of the transmit array may be periodically positioned every other transducer element of the receive array, or vice versa. In some variations, all alternating transducer elements may belong to one type of array (transmit or receive). In some variations, the transmit array and the receive array may not be interleaved with each other (i.e., may not spatially overlap). In some variations, the processor of the second device may process feedback signals received by one or more transducer elements of the receive array to generate feedback signal data and may use interpolation and / or extrapolation of the feedback signal data based on the relative spatial positions or geometries of the transmit and receive array elements to determine a transducer configuration for efficiently transmitting power / data to the first device.

[0264] FIG. 9 illustrates a variation in which each alternating transducer element may belong to either a transmit array or a receive array. The feedback signal (952) generated from the first device (910) may include one or more reflected signals, an active uplink signal transmitted by the first device, etc. In some variations, the amplitude, phase, and / or time delay of the feedback signal (952) received by the transducer elements of the receive array (e.g., R1-R4) can be processed to estimate which transducer elements of the transmit array (e.g., T1-T3) may be selected to include the transducer configuration and its drive signal. For example, the feedback signal (952) coming from the first device and directed to R3 and R4 may be attenuated or scattered by the ribs (972), causing R3 and R4 to receive a feedback signal (952) with a very small amplitude. In this example, because T3 is between R3 and R4, the processor of the second device may determine that the link between T3 and the first device may also be shielded by rib 972. Therefore, T3 may not be selected to transmit a signal to the first device 910.

[0265] In some variations, the processor of the second device can determine drive signals for one or more transmit array elements using a geometric relationship between the estimated location of the first device, the location of one or more elements of the receive array, and the location of one or more elements of the transmit array. For example, based on the received phase, time delay, and / or amplitude of the feedback signal (952) at R1 and R2 and the geometric relationship between R1, R2, and T1, the processor of the second device can estimate (e.g., calculate an average value) the exact or approximate phase, time delay, and / or amplitude of the feedback signal, which can be accurately estimated, at the location of T1 and use it to drive T1 with the appropriate phase, delay, and / or amplitude when transmitting power to the first device (e.g., using time reversal).

[0266] In some variations, the first device (e.g., an IMD) can be configured to generate a wireless signal (e.g., an active uplink or feedback signal, a reflected signal, a modulated backscatter signal, etc.), and the second device can include a first transducer array, a second transducer array, and a processor. The first transducer array can be configured to receive the wireless signal from the first device, the processor can be configured to generate first device data based on the received wireless signal, and the second transducer array can be configured to exchange one or more of wireless power and wireless data with the first device based on the first device data. For example, the first transducer can be configured to locate (e.g., locate) the first device, while the second transducer array can be configured to efficiently exchange power and / or data with the first device. In some variations, the first device data may include one or more of parameters associated with the first device (e.g., the spatial location of the first device) and parameters associated with the wireless signal generated by the first device (e.g., the phase, time delay, amplitude, frequency, encoding data of the wireless signal). In some variations, the transducer elements of the first transducer array configured for localization may include a higher impedance at the operating frequency (e.g., to increase sensitivity to received wireless signals) compared to the second transducer array elements used to transmit power to the first device.

[0267] In some variations, the first transducer array and the second transducer array may each include an ultrasound transducer array. In some variations, the second transducer array may include a one-dimensional linear array or a two-dimensional array. In some variations, the first transducer array may include at least three non-collinear transducer elements. The non-collinear transducer elements may be configured to perform triangulation of the first device based on wireless signals generated by the first device. In some variations, the first transducer array and the second transducer array may include separate transducer elements. In some variations, the first transducer array and the second transducer array may include at least one identical (e.g., shared) transducer element. For example, the second transducer array may include a 1D linear array, and the first transducer array may include two transducer elements at the ends of the 1D linear array and a third transducer element that may not be part of the second transducer array and may not be collinear with the two end transducer elements. In contrast, each element of the 1D linear array is collinear, preventing triangulation from locating the first device. In some variations, the first transducer array may include transducer elements positioned at or near the four corners of a rectangular second transducer array. In some variations, the first transducer array may include a subset of the second transducer array.

[0268] In some variations, the second device may include a third transducer array configured to transmit an interrogation signal to the first device. The wireless signal generated by the first device may include a feedback signal generated in response to the interrogation signal. In some variations, the third transducer array may be a subset of either the first transducer array or the second transducer array and may include one or more transducer elements. In some variations, the third transducer array may include transducer elements separate from each of the first transducer array and the second transducer array. In some variations, one or more transducer elements of the second transducer array may be configured to receive a wireless signal from the first device. In some variations, the wireless signal may include wireless data (e.g., physiological data). In some variations, the one or more transducer elements of the first transducer array and the second transducer array may be interleaved or interspersed. In some variations, the second transducer array may be configured to exchange one or more of wireless power and wireless data with the first device based at least in part on one or more of interpolation and extrapolation of one or more parameters of the received wireless signal. For example, to determine the phase of the second transducer array element for transmitting power (e.g., using time reversal), the phase corresponding to the received wireless signal on the first transducer array element may be interpolated or extrapolated based on the relative spatial positions of the first and second transducer array elements.

[0269] g. User prompts In some variations, because the exact location of the first device is unknown, the patient may face challenges in aligning an external second device on the body with a first device placed inside the patient. For example, the first device (e.g., an IMD) may be implanted within the patient's body to monitor one or more physiological parameters. The patient may be provided with a second device (e.g., an external wireless device) to wirelessly recharge and communicate with the first device.

[0270] In some variations, one or more transducer elements of the second device can be configured to transmit an interrogation signal for interrogating the first device, as described herein. One or more transducer elements of the second device can be configured to receive a feedback signal that can be transmitted by the first device in response to the interrogation signal. In some variations, the received feedback signal can be processed by a processor of the second device to generate feedback signal data, and a user prompt for adjustment (e.g., repositioning) of the second device can be provided based on the feedback signal data.

[0271] In some variations, a user prompt including a location notification may be generated to instruct the user to reposition the second device based on the feedback signal. In some variations, generating the location notification may be based on an estimation of the spatial path of the first device. In some variations, the second device may be configured to measure the strength of the received feedback signal on different transducer elements. The second device may be configured to determine whether the second device is aligned with the first device. For example, if the transducer elements toward the left side of the second device receive a stronger (higher amplitude) feedback signal from the first device compared to the right side of the second device, the center of the second device may be better aligned with the first device if the second device is moved to the left. In some of these variations, a user prompt or location notification may be generated instructing the user to spatially adjust the second device toward the left so that the second device is more favorably centered or positioned to provide power to the first device, thereby improving wireless link efficiency.

[0272] In some variations, the relative power and / or voltage amplitude of the feedback signals as received by different transducer elements of the second device can be compared. Based on the results of the comparison, a user prompt can instruct the user to reposition the second device so that an element closer to the center of the transducer array of the second device, or a preferred transducer element of the second device (e.g., known to be highly efficient or known to function properly), can be centered or positioned closer to the first device.

[0273] In some variations, the second device can be configured to cycle through different transducer elements to transmit interrogation signals in any order, including a predetermined order in some variations. In some variations, feedback signals received by three or more transducer elements of the second device can be processed to perform triangulation and determine the approximate location of the first device relative to the second device. In some of these variations, the feedback signal data can include data corresponding to the location of the first device (e.g., the X, Y, and / or Z coordinates of the first device). In some variations, data corresponding to the location of the first device derived from the feedback signals can be used to instruct the user, via a user prompt, to spatially align or center the second device relative to the first device (e.g., when the first device is located near the central axis of the second device).

[0274] In some variations, a user prompt can be generated to instruct the user to spatially adjust the second device so that the first device is advantageously positioned relative to a predetermined set of transducer elements of the second device. For example, if different transducer elements of the second device include different efficiencies (e.g., electrical-to-acoustic conversion efficiencies) and / or impedance characteristics, the predetermined set of transducer elements can include a higher efficiency and advantageous impedance profile to achieve a high overall link efficiency with the first device.

[0275] In some variations, the spatial alignment can include aligning the axis of the second device with the spatial path of the first device. For example, in some variations, the second device can include a one-dimensional (1D) linear ultrasound transducer array, and the spatial alignment can include aligning one or more of the aperture and elevation angle of the array with the spatial path of the first device. Aligning the elevation angle of the 1D array primarily along the spatial path of the first device can allow for a larger beamwidth along the elevation direction (e.g., several centimeters). A sufficiently large beamwidth can ensure that the first device remains substantially focused, even during operation. An advantage of aligning the aperture of the 1D array primarily along the spatial path of the first device can be that the beam can be steered in that direction by phasing the array elements, thereby enabling tracking of the first device during movement.

[0276] In some variations, a power notification can be generated that includes the power status of one or more of the first device and the second device. In some variations, a user can recharge the first device and / or the second device based on the power notification. In some variations, a communication notification can be generated that corresponds to one or more of the data received from the first device, the physiological parameter data, and the parameter data of one or more of the first device and the second device. The data can be provided to a medical professional and used to guide the patient's treatment.

[0277] h. Access Period In some variations, a first device (e.g., an IMD) implanted in the heart may move and / or rotate along a spatial path (e.g., an orbit) relative to a second device (e.g., an external wireless device). For example, this may be due to the pumping action and / or breathing of the heart. Due to such movement, the first device may be able to efficiently receive and transmit wireless signals from the second device only during a portion of the spatial path. The duration that the first device resides in the efficient portion of the spatial path is referred to as an access period and is described in connection with FIG. 10 .

[0278] In some variations, the access period (1092) may be short relative to the cardiac cycle (1090), as shown in FIG. 10 . This may be true for systems that can use ultrasonic energy for wireless power and wireless data transfer, as the spot size of the ultrasound beam may be on the millimeter scale, while the spatial path (1080) of the first device or IMD (1010) may span several centimeters. In some variations, the spatial path of the first device may be tracked by the second device, and one or more transducer configurations of the second device may be determined for multiple different positions of the first device along the spatial path. This technique may be useful for maintaining a wireless link throughout the spatial path. In some variations, different approaches, such as those described herein, may be used to exchange wireless signals with a moving first device. In some variations, such approaches may involve exchanging wireless signals with the first device only during one or more access periods.

[0279] In some variations, an access period prediction technique can be used to determine and / or predict the access period. In some variations, the first device can be configured to measure physiological parameters (e.g., cardiac parameters such as pressure, heart rate, etc., and / or respiratory rate, etc.) and can be configured to predict or determine the access period based on the parameters. For example, a first device implanted in the left ventricle (LV) can measure a blood pressure waveform within the LV. A duration during which the pressure within the LV is relatively stable or constant can correspond to a duration during which the first device is relatively stationary with respect to the second device, and corresponds to the access period.

[0280] In some variations, as shown in FIG. 11 , the second device can be configured to measure physiological parameters (e.g., cardiac parameters such as ECG, heart rate, heart sounds, blood pressure, etc., and / or respiratory rate, etc.) and can be configured to predict or determine an access period based on the parameters. For example, the second device, such as an external wireless device, can be configured to measure a heart rate or ECG signal (1110). Additionally or alternatively, the second device can measure audible sounds (1120), as shown in FIG. 11 . Based on the measured ECG and / or audible sound signals, the second device can be configured to determine a start time (1130) of the access period during the cardiac cycle. For example, the start time (1130) of the access period (1192) can be set to a predetermined time delay (e.g., approximately 100 ms) after the detection of a heart sound (e.g., S2). In some variations, the access period can occur during diastole.

[0281] In some variations, the access period may be predicted or determined based on current measurements of one or more cardiac parameters or other data. In some variations, the access period may be predicted based on previous measurements of one or more cardiac parameters or other data.

[0282] In some variations, the first device and / or the second device can be configured to periodically query another device to predict or determine the access period without relying on any cardiac parameter measurements. For example, the second device can transmit periodic beacons to the first device and wait for the first device to acknowledge receipt of the beacons. Upon receipt of the acknowledgement, the second device can be configured to perform a signal exchange with the first device (e.g., transfer wireless power to the first device).

[0283] i. Uplink data transfer Reliable uplink data transfer from a first device (e.g., an IMD) to a second device (e.g., a wireless device) can enable accurate recovery of physiological data from the body for use in therapy. In some variations, ultrasound uplink signals transmitted from a first device implanted adjacent to the heart may experience reflections (e.g., multipath propagation) from various tissue structures or boundaries (e.g., ribs, lungs, etc.) in one or more directions. The reflections may interfere with the uplink data received by the second device and may introduce errors into the data decoded by the second device.

[0284] In some variations, the transducer configuration (e.g., subarray) of the second device can be selected to receive beamforming to the location of the first device based on localization of the first device using any of the techniques described herein. In some variations, uplink data can be transferred from the first device to the second device in one or more uplink data intervals, similar to interval-based powering, as described herein. This can be beneficial for a first device that may move / rotate relative to the second device over time. In some variations, the second device can transmit a signal (e.g., including digital data bits) to the first device acknowledging receipt of the data in the uplink data interval. For example, the second device can acknowledge receipt of the data based on a comparison of the number of received uplink data bits with the expected number of uplink data bits corresponding to the uplink data interval. In some variations, the first device can be configured to retransmit the corresponding data bits in the next uplink data interval when the first device does not receive an acknowledgment signal from the second device until receipt is acknowledged by the second device.

[0285] In some variations, the wireless link between the first device and the second device may be obstructed (e.g., shielded) by tissue structures such as ribs or lungs. In some of these variations, intermittent uplink data transfer may be performed in a manner similar to intermittent power supply. If the link gain between the first device and the second device is determined to be unfavorable, uplink data may not be transferred in one or more uplink data intervals. In some variations, uplink data transfer may resume after a predetermined time delay. For example, after the predetermined time delay, the second device may be configured to transmit an interrogation signal to the first device. Based on the feedback signal received from the first device, a transducer configuration for efficiently receiving uplink data from the first device may be selected.

[0286] In some variations, digital uplink signals received by different transducer elements of the second device may be processed by a processor of the second device to decode uplink signal data. For example, in some variations, at least a first transducer element of the second device may receive an uplink signal with a sufficient SNR for a first portion of the spatial path of the first device. At least a second transducer element of the second device may receive an uplink signal with a sufficient SNR for a second portion of the spatial path of the first device. In some variations, the processor of the second device may be configured to process the uplink signals received by at least the first and second transducer elements to decode data bits. The processor may combine or combine the data bits together to recover all data bits transmitted by the first device. This technique may be extended to any number of transducer elements of the second device.

[0287] In some variations, the processor can determine when an uplink data transfer from the first device to the second device is completed and / or whether it is interrupted for any reason (e.g., similar to why a power transfer may be interrupted). The first device and / or the second device can be appropriately configured to prevent data from being lost. In some variations, the second device can transmit a signal to the first device acknowledging receipt of data previously transmitted by the first device to the second device (e.g., in a previous uplink data interval). In some variations, the first device can erase or overwrite a data packet in memory only after the data packet is successfully transmitted to the second device and receipt is acknowledged by the second device. In some variations, if the first device does not receive an acknowledgement from the second device for a previously transmitted data packet, it can retain the data packet in memory and retransmit it until an acknowledgement signal is received from the second device.

[0288] In some variations, as an example, the first device may track one or more pointers (e.g., memory address pointers) in its memory. The pointers may encode addresses or starting addresses of data blocks that may have already been transmitted to and / or acknowledged by the second device and / or addresses or starting addresses of data blocks that may not yet be transmitted to the second device. Based on acknowledgements received from the second device, the first device may update one or more of the pointers. In some variations, the first device may be configured to uplink the values ​​of the one or more pointers to the second device using a feedback signal or uplink data.

[0289] In some variations, the second device can notify the user based on a user prompt if the uplink data transfer is interrupted or if a certain percentage of the data transfer may have been completed by a predetermined point in time. For example, the difference between two pointers described herein (e.g., one pointer pointing to transmitted / acknowledged data blocks and another pointer pointing to data blocks not yet transmitted to the second device) can indicate the percentage of data successfully received by the second device.

[0290] In some variations, the first device can be configured to stop transmitting uplink data to the second device. For example, the feedback signal from the first device can encode the value of a pointer to its memory, as described herein, based on which the second device can send a command to the first device to stop transmitting uplink data when all of the data in the memory of the first device has been successfully read by the second device. In some variations, the first device can automatically stop transmitting uplink data to the second device when the stored data has been transmitted and acknowledged by the second device.

[0291] In some variations, the second device may generate a user prompt including, but not limited to, the percentage of the first device's data that has been successfully received by the second device, whether the uplink data transfer is complete, whether the uplink data transfer was interrupted for any reason, combinations thereof, etc. Based on the user prompt, the user may take an action such as recharging the battery of the second device if the battery of the second device is low, repositioning the second device if it is misaligned, turning off and removing the second device if the uplink data transfer is complete, combinations thereof, etc.

[0292] j. Selecting the transducer for the first device In some variations, the first device (e.g., an IMD) may comprise multiple transducer elements (e.g., multiple ultrasonic transducer elements) that can be individually selected for different operations, including transmitting uplink signals (e.g., feedback signals, data), receiving power, receiving downlink signals (e.g., downlink data, commands), combinations thereof, etc. The selection of the transducers in the first device may enable robust and error-free data communication with the second device (e.g., an external wireless device, a wireless device).

[0293] In some variations, the first device (e.g., an IMD) may include a plurality of transducers configured to receive downlink signals. The second device (e.g., a wireless device) may be configured to transmit the downlink signals. One or more of the plurality of transducers may be configured to exchange one or more of wireless power and wireless data with the second device based on the received downlink signals. In some variations, the selection of one or more transducer elements of the first device may be performed by the first device by processing one or more downlink signals received from the second device, including one or more of an interrogation signal, power, downlink commands, other downlink signals, etc. In some variations, the selection of one or more transducer elements of the first device may be performed by the second device by processing one or more uplink signals received from the first device, including one or more of a feedback signal, uplink data, etc., and communicating this data to the first device using downlink commands (e.g., the second device may program the first device to use one or more particular transducer elements for operation).

[0294] In some variations, the selection of one or more transducer elements of the first device for operation can be based on determining the one or more transducer elements that received the highest power or voltage, or a power or voltage above a predetermined threshold, from a downlink signal, such as an interrogation signal. The selection of transducer elements of the first device can be similar to the selection of transducer elements of the second device based on received feedback signals described herein.

[0295] In some variations, only one transducer element of the first device may be selected for operation (e.g., receiving power, receiving downlink signals, transmitting uplink signals). For example, a processor of the first device may be configured to process an interrogation signal received by each of the transducer elements, determine the transducer element that received the highest power or voltage from the interrogation signal, and select that transducer element for transmitting an uplink signal, such as uplink data. In some variations, the first device may include multiplexer and / or demultiplexer circuitry comprising a switch or switch network that may be coupled to the transducer elements. In some variations, the switch may be configured to connect only selected transducer elements to an uplink data transmitter to transmit the uplink signal using only the selected transducer elements. This may enable selection of a transducer element having the best link gain with the second device, resulting in a robust data link with a high SNR and low bit error rate. In some variations, one or more of the multiple transducers of the first device may be configured to exchange wireless data with the second device at a first frequency that is different from the second frequency of the received wireless power.

[0296] In some variations, the first device may further include a processor. In some variations, the processor may be configured to select one or more of the plurality of transducers configured to exchange one or more of wireless power and wireless data with the second device based on the received downlink signal. In some variations, the processor may be configured to periodically update the selection based on the one or more of the received downlink signals. In some variations, the processor may be configured to calculate a received signal strength of the downlink signal for one or more of the plurality of transducers and compare the received signal strengths of the one or more of the plurality of transducers with each other. In some variations, the processor may be configured to select one or more of the plurality of transducers corresponding to a received signal strength above a predetermined threshold for exchanging one or more of wireless power and wireless data with the second device. In some variations, the processor may be configured to select one transducer corresponding to a maximum received signal strength for transmitting an uplink signal to the second device. In some variations, the processor may be configured to decode one or more downlink commands based on the downlink signal. In some variations, the processor may be configured to select one or more transducers for exchanging one or more of wireless power and wireless data with the second device based on decoding of one or more of the downlink commands.

[0297] FIG. 12 shows a block diagram of a first device (1210) according to an exemplary variation of this system. The transducer (1220) of the first device (1210) may include multiple transducer elements (1222, 1224, 1226). The first device (1210) may be configured to receive a downlink signal (1240), such as an interrogation signal, power, or the like, from a second device (not shown). Each transducer element (1222, 1224, 1226) may receive a different voltage or power from the downlink signal (e.g., due to the orientation of the transducer element relative to the second device). The voltages (1250) received by the multiple transducer elements (1222, 1224, 1226) may be compared. As shown in FIG. 12, one transducer element (1224) may receive the highest voltage amplitude compared to the other transducer elements (1222, 1226). The processor of the first device (1210) calculates the voltage amplitude (V P1 , V P2 , V P3, each of which may be an open-circuit voltage) to generate a selection signal (including one or more digital control bits) that is provided to a demultiplexer circuit (1236). The input to the demultiplexer circuit (1236) may be an output of a data communication circuit (1234), such as an output of a power amplifier circuit for uplink data transmission. The demultiplexer circuit (1236) may include one or more switches or switch networks that may be configured by a selection signal to connect one transducer element (1224) to an input of the demultiplexer circuit (1236) rather than the other transducer element (1222, 1226) for uplink data transmission. It should be understood that the particular circuit implementation of the demultiplexer circuit discussed herein (using switches) is an example, and that other variations are possible, such as frequency-based selection (e.g., using a filter), amplitude-based selection, using circulators, diodes, or passive devices, etc. Additionally or alternatively, in some variations, the first device (1210) may include a multiplexer circuit (not shown), which may be similar to the demultiplexer circuit for uplink data transmission, in which transducer elements may be selected for operation, such as receiving power or downlink signals (e.g., data, commands). The multiplexer circuit may be configured or controlled by the sensing and processing circuit (1232).

[0298] In some variations, selected transducer elements can be selected for operations such as receiving power from a second device by configuring or connecting only the selected transducer elements to a power circuit, such as a rectifier or AC-DC converter. For example, switches may be implemented between each transducer element and the power recovery circuit (e.g., a rectifier). During power recovery, one or more switches between the selected transducer element and the power recovery circuit may be turned on, and one or more switches between the other transducer elements and the power recovery circuit may be turned off.

[0299] In some variations, selected transducer elements may be selected for operations such as receiving downlink signals (e.g., downlink data, commands, etc.) For example, the processor of the first device may process downlink signals received by only selected transducer elements (e.g., transducer elements receiving the highest voltage or power from the interrogation signal or downlink signal) to decode the downlink data and / or commands.

[0300] In some variations, two or more transducer elements of the first device can be selected for operation. For example, in some variations, the processor of the first device can be configured to measure the relative phase or delay of a downlink signal (e.g., an interrogation signal) received by its transducer elements. The measurement data can be used to drive the transducer elements with the appropriate phase, delay, and / or amplitude for transmitting an uplink signal. This can be useful for avoiding undesired signal cancellation (such as a null lobe) when transmitting signals using two or more transducer elements. In some variations, the first device can transmit uplink signals over multiple transducer elements (e.g., all transducer elements) with the same phase or with the appropriate phase (to minimize design complexity) if it is known or predictable that undesired signal cancellation will not occur. As another example, in some variations, two or more transducer elements of the first device can be configured to receive power from the second device by using techniques such as power or DC coupling. In some variations, each transducer element of the first device may be selected for an operation such as receiving power, receiving a downlink signal, and / or transmitting an uplink signal.

[0301] In some variations, in addition to selecting one or more transducer elements of the first device for operation, the drive signal or the manner in which the signal is received from those transducer elements may also be configured. For example, in addition to selecting one or more transducer elements of the first device, the first device and / or the second device may determine one or more of the frequency, phase, delay, amplitude, power, combinations thereof, etc. of the uplink signal for transmitting.

[0302] In some variations, the selection of one or more transducer elements of the first device (and / or their corresponding drive signals, or the manner in which signals are received therefrom) may be performed at any time during the performance of any of the methods described herein. For example, the selection of one or more transducer elements of the first device and / or the determination of their drive signals (e.g., frequency, amplitude, etc.) may be performed at the start of every uplink data interval during interval-based uplink data transfer.

[0303] k. A first device having a single transducer In some applications, the first device (e.g., an IMD) may include a single transducer (e.g., a single ultrasonic transducer) configured to perform multiple different wireless functions, such as receiving an interrogation signal, receiving power, receiving a downlink data signal, and transmitting an uplink signal. This may allow for miniaturization of the first device. The first device may further include a multiplexer circuit configured to separate the various signals transmitted / received using the single transducer. In some variations, the multiplexer circuit may be controlled by a controller circuit, which in some variations may be a component of the processor of the first device. The multiplexer circuit may be configured for multiple different operations, such as receiving an interrogation signal and power / downlink data from the second device and transmitting an uplink signal to the second device. While the solutions presented below are discussed with respect to a multiplexer circuit including a switch, other variations of the multiplexer circuit, such as those described above, may be applicable here.

[0304] In some variations, the first device may include a wake-up receiver circuit configured to detect an interrogation signal received by the first device from the second device. The wake-up receiver circuit may include one or more of an envelope detector circuit, a code detector or decoder circuit, a combination thereof, and the like. In some variations, the wake-up receiver circuit may be coupled to a multiplexer circuit. The multiplexer circuit may be controlled by a controller circuit to couple (e.g., connect using a switch) the wake-up receiver circuit to the transducer in a default operating mode. For example, the default operating mode may be the mode of the first device before receiving a predetermined interrogation signal. For example, in the default mode, the first device may autonomously perform functions such as sensing, or may not perform any functions (i.e., may be in a sleep state). This configuration of the multiplexer circuit may enable the first device to be ready (e.g., be in a standby state) to detect any ad-hoc interrogation signal transmitted by the second device.

[0305] In some variations, the multiplexer circuitry can be configured such that the power recovery circuitry (e.g., a rectifier) ​​remains disconnected from the transducer in a default mode. When an interrogation signal is received, the wake-up receiver circuitry can detect the interrogation signal (e.g., via envelope detection) and generate a wake-up signal that can be provided to the controller circuit. In some variations, the wake-up receiver circuitry can generate the wake-up signal when the amplitude of the interrogation signal exceeds a threshold, or has a specific code or embedded command, or both.

[0306] In some variations, the controller circuit, upon receiving the wake-up signal, can control the multiplexer circuit to connect the power recovery circuit to the transducer, thereby enabling the first device to recover power from a power signal subsequently transmitted to the first device by the second device.

[0307] In some variations, the controller circuit can control the multiplexer circuit to couple the transducer to the transmitter circuit upon receiving a wake-up signal to transmit an uplink signal (e.g., a feedback signal) to the second device. For example, the first device can be configured to sample the amplitude of a received interrogation signal, digitize it, and then transmit the digitized amplitude as a feedback signal to the second device. Additionally or alternatively, the feedback signal may include one or more analog pulses and / or one or more digital bits to acknowledge receipt of the interrogation signal by the first device to the second device. Upon receiving one or more of the feedback signals, the second device can perform localization of the first device and / or select a transducer configuration to establish an efficient link with the first device. In some variations, the second device can then transmit power to the first device. In some variations, the controller circuit of the first device can control the multiplexer circuit to decouple the transducer circuit from the transducer upon transmission of the feedback signal. In some variations, simultaneously with or after disconnecting the transmitter circuit, the controller circuit may control the multiplexer circuit to couple the transducer with a wake-up receiver circuit (i.e., return to default mode and wait for another interrogation signal from the second device), or to couple with a power recovery circuit (to restore power transmitted from the second device).

[0308] In some variations, after receiving the feedback signal from the first device, the second device can transmit a command or code to the first device indicating that it should next transmit a power signal. In some variations, the wake-up receiver circuit can detect such a code and provide a corresponding signal to the controller circuit. The controller circuit can then couple the power recovery circuit to the transducer to configure the first device to receive power.

[0309] In some variations, the controller circuit can control the multiplexer circuit to disconnect the transducer from the power recovery circuit after the power supply is terminated. The controller circuit can then reconnect the transducer to the wake-up receiver circuit (i.e., return to default mode). In some variations, the controller circuit can control the multiplexer circuit to disconnect the transducer from the power recovery circuit after the power supply is terminated. The transducer can then be coupled to the transmitter circuit to send a feedback signal to the second device (e.g., communicating the energy state of the first device). The transducer can then be coupled to the wake-up receiver circuit (i.e., return to default mode). In some variations, the second device can communicate the termination of the power supply to the first device. In some variations, the first device can automatically perform these steps after a falling edge of the received power signal (e.g., based on a timeout).

[0310] In some variations, the multiplexer circuitry can be configured to leave both the wake-up receiver circuitry and the power recovery circuitry coupled to the transducer in a default mode, which may enable the first device to recover power and / or charge its energy storage device from the interrogation signal.

[0311] l. Downlink signal amplitude detection In some variations, the second device can use the first device data to adjust transmit power for the first device and / or select a transducer configuration for efficient wireless power / data exchange with the first device. In some variations, the first device (e.g., an IMD) can be configured to detect the amplitude of a received downlink signal, such as an interrogation signal, a power signal, downlink data, etc. For example, the first device can be configured to detect the amplitude of a downlink signal (e.g., an ultrasonic transducer peak voltage) received from the second device (e.g., a wireless device). The amplitude can be compared to a threshold or digitized. A feedback signal including the digitized amplitude or the comparison result can be sent to the second device.

[0312] In some variations, the first device may include a first envelope detector circuit coupled to the ultrasonic transducer of the first device to generate a first output voltage corresponding to the voltage amplitude of the downlink signal received by the ultrasonic transducer. The first envelope detector circuit may include a peak detector circuit, a rectifier, etc. In some variations, the first output voltage may be proportional to or equal to the amplitude of the voltage received by the ultrasonic transducer of the first device, or the maximum value of that voltage. For example, the first envelope detector circuit may include a diode in series with a parallel combination of a capacitor (C1) and a resistor (R1). In some variations, R1 may be very large or infinite (i.e., no resistor).

[0313] In some variations, a time or sampling trigger can be determined that allows the first device to sample the first output voltage. In some variations, the first device can be configured to sample the first output voltage of the first envelope detector circuit to estimate a voltage amplitude received by the ultrasonic transducer.

[0314] In some variations, the first device may include a second envelope detector circuit coupled to the ultrasonic transducer of the first device to determine a sampling trigger. The second envelope detector circuit may be configured to generate a second output voltage corresponding to the voltage amplitude of the downlink signal received by the ultrasonic transducer. In some variations, the second envelope detector circuit may be configured to have a faster response time than the first envelope detector circuit. For example, the second envelope detector circuit may include a diode in series with a parallel combination of capacitor C2 and resistor R2, such that the output time constant C2R2 is smaller (e.g., more than 10 times smaller) than the output time constant C1R1 of the first envelope detector circuit. Thus, the second output voltage may fall faster than the first output voltage upon a falling edge of the downlink signal. In some variations, the falling transition of the second output voltage may be used directly or processed (e.g., using one or more inverters) to generate a sampling trigger for sampling the first output voltage. The sampled first output voltage may represent the amplitude of the downlink signal received by the ultrasonic transducer of the first device.

[0315] In some variations, a timer or delay generator circuit may be configured to sample the first output voltage for a predetermined duration after receipt (or a rising edge) of the downlink signal by the first device. In some of these variations, the second envelope detector circuit is not required.

[0316] m. Mode query of the first device For the system to function properly, the first device can be configured to detect interrogation events and respond appropriately to the interrogation. In some variations, the first device (e.g., an IMD) can operate in a first mode by default. For example, the first mode can be a sensing mode in which the first device can be configured to periodically sense a physiological parameter. The first mode can also be a sleep mode in which the first device is dormant and can wait for an interrogation signal from a second device (e.g., a wireless device). During the first mode, the first device can be interrogated by the second device to recharge the first device's energy storage device (e.g., a battery) and / or to exchange data.

[0317] In some variations, the first device may include a wake-up receiver circuit configured to monitor ultrasonic signals received by one or more ultrasonic transducers of the first device. In some variations, the wake-up receiver circuit may be configured to detect a signature or code encoded in the interrogation signal by the second device to determine the purpose of the interrogation (e.g., whether the second device intends to recharge the first device, or whether the second device intends to restore data stored in the first device). In some examples, the wake-up receiver circuit may include an envelope detector, a comparator, and a decoder circuit.

[0318] In some variations, the first device can respond to the interrogation signal of the second device using a feedback signal. Additionally or alternatively, a handshake of one of one or more signals can be exchanged between the second device and the first device. In some variations, the first device can configure itself to cease the first mode and initiate a second mode of operation upon detection of the interrogation signal (i.e., the interrogation signal can cause the first device to disable its first mode of operation and enter the second mode). For example, the second mode may include a wireless uplink mode in which the first device can configure itself to transmit its stored data using at least one uplink signal. In some variations, the first device can configure itself to operate in a second mode in addition to the first mode upon detection of the interrogation signal. For example, the second mode may be a wireless uplink mode, and the first mode may be a sensing mode. The first device can be configured to time-multiplex or simultaneously perform functions corresponding to the two modes. In some variations, the uplink data transfer may occur over one or more intervals (e.g., interval-based data transfer similar to interval-based powering), which may assist in recovering data from a moving first device. After the data transfer is complete, the first device may automatically return to the first mode. In some variations, the second device may be configured to send a command to the first device using a downlink signal to return the first device to the first mode before or after completion of the uplink data transfer.

[0319] In some variations, additionally or alternatively, based on one or more feedback signals, the second device may generate a user prompt (e.g., feedback) instructing the user to manually adjust the second device if doing so could improve signal (power, data) exchange in the second mode. In some variations, if no feedback signal is received when queried, or based on one or more received feedback signals, the second device may generate a user prompt instructing the user to consult a medical professional.

[0320] F. Gauge pressure estimation In some variations, the first device (e.g., an IMD) can be configured to directly measure absolute pressure corresponding to blood pressure, such as in a heart chamber or blood vessel. For example, the absolute pressure value can be referenced to a vacuum or a known pressure. Gauge pressure can be estimated from the absolute pressure measurement. Gauge pressure can be referenced to ambient air pressure or atmospheric pressure. Gauge pressure can be predetermined by subtracting atmospheric pressure from the absolute pressure measured by the first device. Thus, in some variations, absolute pressure measurements by the first device, along with corresponding atmospheric pressure measurements, can enable accurate determination of gauge pressure for disease monitoring and treatment. Systems, devices, and methods for estimating gauge pressure from measured absolute pressure are described herein.

[0321] In some variations, left ventricular end-diastolic pressure (LVEDP) can be measured to monitor the progression of a patient's heart failure. LVEDP values ​​(which may be gauge pressure values) are typically low, for example, in the range of about 0 mmHg to about 40 mmHg. Atmospheric or ambient pressure at a patient's location can vary and may depend on several factors, including, but not limited to, weather conditions, ambient temperature, whether the patient is on an airplane, the patient's altitude relative to sea level, or a combination thereof. For example, atmospheric pressure at sea level may be about 760 mmHg, while at an altitude of about 500 m it may be about 720 mmHg (a difference of 40 mmHg, or about LVEDP, compared to sea level). Therefore, accurate determination of atmospheric pressure may be important for accurate estimation of LVEDP, and blood pressure in general. In some variations, a second device (e.g., an external wireless device) can be configured to measure atmospheric pressure. In some variations, the first device can measure absolute pressure within the body independently of the second device, i.e., without being simultaneously interrogated or commanded to measure pressure by the second device. For example, the implanted first device can be configured to monitor blood pressure continuously throughout the day (e.g., the first device can be battery-powered). The second device need not be placed on the patient's chest or carried by the patient at all times.

[0322] In some variations, the second device or any external device can be configured to measure atmospheric pressure. For example, in some variations, the second device configured to power and / or communicate with the first device can also include an air pressure sensor or pressure sensor configured to measure atmospheric pressure. In some variations, the air pressure sensor may be located on an external device such as a phone, smartwatch, tablet, etc. Additionally or alternatively, an application such as a mobile app may be configured to run on the external device and record and / or process atmospheric pressure values. In some variations, the second device or any external device can obtain atmospheric pressure values ​​from the internet or another device. In some variations, the patient can carry the second device or external device configured to obtain, record, and / or process atmospheric / ambient pressure values. For example, the second device configured to measure atmospheric pressure may be attached to the patient's mobile phone or placed in a wallet or bag that can be carried with the patient. In some variations, the second device may be worn on the body (e.g., in the form of a patch, sleeve, strap, belt, etc.).

[0323] In some variations, the absolute pressure measurements taken by the first device can be post-processed (e.g., software processing) by the second device to estimate gauge pressure. Post-processing can identify features or signatures of atmospheric pressure or atmospheric pressure fluctuations in the absolute pressure data. These features or fluctuations can be subtracted to determine gauge pressure. For example, post-processing can include using a low-pass or high-pass filter to remove atmospheric pressure fluctuations from the absolute pressure data. In some variations, atmospheric pressure may change at a slower rate than blood pressure. In some variations, if a significant deviation in absolute pressure is detected, software processing can attribute this to changes in atmospheric pressure. In some variations, post-processing can be based on data such as the patient's travel history (e.g., travel time / location) to estimate atmospheric pressure and then gauge pressure.

[0324] In some variations, the first device can be configured to measure or estimate atmospheric pressure. In some variations, the first device can be configured to measure or determine gauge pressure and / or a pressure correlated to gauge pressure by measuring both an absolute pressure of interest (e.g., absolute blood pressure in the LV, any physiological pressure changes in a tissue or organ of interest) and an estimate or surrogate of atmospheric pressure. For example, in some variations, the first device can include a first pressure transducer disposed in a heart chamber or a lumen of a blood vessel. The first pressure transducer is directly affected by or can directly sense blood pressure. The first device can further include a second pressure transducer positioned or disposed in a location that is not directly affected by or cannot directly sense blood pressure (e.g., inside the heart wall or septum). In some variations, processing (e.g., subtracting one from the other) the signals measured by the first pressure transducer and the second pressure transducer can provide one or more of a desired gauge pressure, a surrogate for gauge pressure, or a pressure that can be correlated to gauge pressure. In some variations, a single pressure transducer may include a first portion located inside a heart chamber or blood vessel lumen and a second portion disposed in a location that may not be directly affected by or sense blood pressure (e.g., inside the heart wall or septum). In some variations, a different first device (e.g., another IMD) may be configured to measure atmospheric pressure. For example, a first device may be implanted just below the skin (e.g., a few mm below the skin on the arm) to measure atmospheric pressure or a reference pressure that can be used to determine gauge pressure from absolute blood pressure measured by another first device.

[0325] In some variations, time synchronization between absolute blood pressure measurements and atmospheric pressure measurements can be used to accurately subtract atmospheric pressure data from absolute blood pressure data to estimate gauge pressure. For example, atmospheric pressure measured by a different device (e.g., by a second device, an external device, or a different first device) can be compared to the absolute blood pressure measurement of a first device placed inside the body. In some variations, the first and second devices can be time-synchronized at a certain point in time, after which both devices can record pressure data at a fixed rate. For example, the second and / or external device (e.g., a phone) and the first device can be synchronized at 9:00 a.m. on a given day, after which the first device can record one or more absolute blood pressure values ​​approximately every five minutes. The second and / or external device (e.g., a phone) can record one or more atmospheric pressure values ​​approximately every five minutes. The first device can store the absolute blood pressure values ​​in memory. Additionally or alternatively, the first device can store one or more time points (e.g., time, date, values ​​corresponding to a counter or timer of the first device, etc.) corresponding to one or more of the stored absolute blood pressures. After a subsequent period of time (e.g., after one or more hours, several days, etc.), the second device can download the absolute blood pressure data from the first device (e.g., via uplink data transfer). The second device can align or synchronize the time points of the absolute blood pressure data of the first device with the time points of the barometric pressure data of the second device (or external device) and then perform a subtraction to determine a gauge pressure value at one or more time points.

[0326] G. Ultrasound Imaging In some variations, the first device (e.g., an IMD) can be configured to sense (e.g., measure) one or more physiological parameters (e.g., blood pressure) in conjunction with an imaging technique (e.g., transthoracic echocardiography, or TTE) for measuring one or more physiological parameters (e.g., blood flow). Measurements using multiple modalities can improve patient diagnosis, monitoring, and treatment (e.g., appropriate adjustment of medication). For example, a first device implanted in a heart chamber or blood vessel can be configured to measure blood pressure, and the TTE can measure blood flow or velocity to assess one or more structures or motion of the patient's heart or heart chamber (e.g., flow or velocity through the left ventricular outflow tract, LV contraction or LV wall motion, thickness / motion of prosthetic valve leaflets, etc.). In some variations, the TTE can be one of the imaging techniques configured to diagnose and / or monitor patients with heart failure, valvular heart disease, prosthetic valve dysfunction, combinations thereof, etc. TTE imaging combined with sensing by the first device can generate interference. For example, TTE imaging can couple ultrasound signals into the pressure transducer of the first device, corrupting the sensed pressure data. Similarly, if the first device transmits ultrasound signals (e.g., for uplink data transfer) during a TTE procedure (e.g., during CW Doppler imaging for blood flow velocity measurement), it can interfere with the ultrasound signals, resulting in errors or corruption of the TTE data or images.

[0327] In some variations, ultrasound signals (e.g., interrogation signals, downlink data, commands, etc.) transmitted by the second device to the first device can encode a specific code (e.g., ID, command). Upon detecting (e.g., decoding) such a code, the first device can respond to the received signal. Signal encoding can reduce erroneous signal transmissions (e.g., feedback signals, ultrasound response signals) generated due to imaging procedures such as TTE.

[0328] In some variations, the first device can be configured to operate in a first mode, such as a sensing mode, during periods when ultrasound imaging, such as TTE, is not being performed. In the sensing mode, the first device can be configured to periodically monitor or sample a physiological parameter, such as blood pressure, and store the physiological parameter data in its memory. For example, the first device in the sensing mode can be configured to perform one or more of the following: sampling blood pressure, processing the sampled pressure values ​​(e.g., calculating peak pressure, average pressure, ignoring certain values, combinations thereof, etc.), storing the processed data (or physiological parameter data) in its memory, receiving wireless signals (e.g., interrogation signals, power, downlink data, commands, etc.) from the second device, transmitting wireless signals (e.g., feedback signals, uplink data) to the second device, combinations thereof, etc. In some variations, prior to initiating an ultrasound imaging procedure, such as TTE, the second device can configure the first device (e.g., via a downlink command) to operate in a second mode (e.g., a waveform storage mode) during periods when ultrasound imaging, such as TTE, is being performed. For example, the first device in the second mode can sample pressure multiple times over one or more cardiac cycles and store the pressure data points in its memory. The samples can be used to diagnose and / or monitor the patient. For example, the samples can be processed to plot a waveform of pressure over one or more cardiac cycles. In some variations, the techniques described herein for reducing coupling between ultrasound signals and pressure transducers can be applied in a manner similar to reducing coupling between TTE signals and the pressure transducer of the first device.

[0329] In some variations, a first device with limited memory capacity can transmit data to a second device before operating in waveform storage mode. For example, the second device can download data (e.g., data captured during sensing mode) from the memory of the first device (e.g., via uplink data transfer) to free up some or all memory space before operating in waveform storage mode (e.g., the first device can transfer the data to the second device and erase its memory after receiving a signal from the second device acknowledging receipt of the data). This can allow one or more pressure waveforms to be stored in the first device.

[0330] In some variations, ultrasound imaging such as TTE may be performed to measure one or more physiological parameters after the first device is configured in a second mode (e.g., a waveform storage mode). For example, the first device may be configured to operate in the second mode to sense and store a pressure waveform (e.g., an LV pressure waveform) over one or more cardiac cycles...

Claims

1. 1. A system configured to exchange wireless power or wireless data, comprising: a first device configured to generate a wireless signal; a second device comprising a first transducer array, a second transducer array, and a processor; the first transducer array is configured to receive the wireless signal from the first device; the processor is configured to generate first device data based on the received wireless signal; a second device, wherein the second transducer array is configured to exchange one or more of wireless power and wireless data with the first device based on the first device data.

2. The system of claim 1 , wherein the first device comprises an implantable medical device and the second device is configured to be placed external to the patient's body.

3. The system of claim 1 , wherein the first transducer array and the second transducer array each include an ultrasound transducer array.

4. The system of claim 1 , wherein the second transducer array comprises a one-dimensional linear array or a two-dimensional array.

5. The system of claim 1 , wherein the first transducer array includes at least three non-collinear transducer elements.

6. The system of claim 1 , wherein the first transducer array and the second transducer array include separate transducer elements.

7. The system of claim 1 , wherein the first transducer array and the second transducer array include at least one identical transducer element.

8. The system of claim 1 , wherein the first transducer array comprises a subset of the second transducer array.

9. 10. The system of claim 1, wherein the second device comprises a third transducer array configured to transmit an interrogation signal to the first device, and the wireless signal comprises a feedback signal generated in response to the interrogation signal.

10. The system of claim 9 , wherein the third transducer array includes transducer elements separate from each of the first transducer array and the second transducer array.

11. The system of claim 1 , wherein one or more transducer elements of the second transducer array are configured to receive the wireless signal from the first device.

12. The system of claim 1 , wherein the wireless signal comprises wireless data.

13. The system of claim 1 , wherein one or more transducer elements of the first transducer array and the second transducer array are interleaved or interspersed.

14. 10. The system of claim 1, wherein the second transducer array is configured to exchange one or more of the wireless power and the wireless data with the first device based at least in part on one or more of interpolation and extrapolation of the wireless signals.

15. 1. A system configured to exchange wireless power or wireless data, comprising: a first device; a second apparatus comprising a processor and a transducer array including a plurality of subarrays, a first subarray configured to transmit an interrogation signal to the first device; a second sub-array configured to receive a feedback signal from the first device; a second device, wherein the processor is configured to cycle through one or more subarrays of the plurality of subarrays until the received feedback signal satisfies a predetermined condition.

16. The system of claim 15 , wherein the first device comprises an implantable medical device and the second device is configured to be placed external to the patient's body.

17. The system of claim 15 , wherein the transducer array comprises an ultrasound transducer array.

18. The system of claim 15 , wherein the subarray comprises one or more transducer elements of the transducer array.

19. The system of claim 15 , wherein the first subarray and the second subarray include the same transducer elements.

20. The system of claim 15 , wherein the predetermined condition comprises a strength of the received feedback signal calculated for one or more transducer elements of the second subarray.

21. 16. The system of claim 15, wherein the processor is configured to select a transducer configuration based on the received feedback signal satisfying the predetermined condition, and the transducer configuration is configured to exchange one or more of the wireless power and the wireless data with the first device.

22. 22. The system of claim 21, wherein the transducer configuration comprises one or more transducer elements of the transducer array.

23. 1. A system configured to exchange wireless power or wireless data, comprising: a first device; a second apparatus comprising a processor and a transducer array including a plurality of subarrays, a first subarray configured to transmit an interrogation signal to the first device; a second sub-array configured to receive a feedback signal from the first device, the feedback signal including one or more of digital first device energy data and digital interrogation signal strength data; a second device, wherein the processor is configured to select a transducer configuration based on the feedback signal, the transducer configuration configured to exchange one or more of wireless power and wireless data with the first device.

24. 24. The system of claim 23, wherein the first device comprises an implantable medical device and the second device is configured to be placed external to the patient's body.

25. 24. The system of claim 23, wherein the transducer array comprises an ultrasound transducer array.

26. 24. The system of claim 23, wherein the subarray comprises one or more transducer elements of the transducer array.

27. 24. The system of claim 23, wherein the first subarray and the second subarray include the same transducer elements.

28. 24. The system of claim 23, wherein the transducer configuration comprises one or more transducer elements of the transducer array.

29. 24. The system of claim 23, wherein the first device comprises a power source including one or more of a rechargeable battery, a capacitor, a supercapacitor, and a non-rechargeable battery.

30. 30. The system of claim 29, wherein the digital first device energy data includes power supply parameters including one or more of voltage, energy level, charging voltage, and charging current.

31. 30. The system of claim 29, wherein the transducer arrangement is configured to wirelessly recharge the power source.

32. 24. The system of claim 23, wherein the interrogation signal comprises a first frequency and the one or more of the wireless power and the wireless data comprises a second frequency different from the first frequency.

33. 33. The system of claim 32, wherein the first device comprises at least one ultrasonic transducer including a first impedance corresponding to the first frequency and a second impedance corresponding to the second frequency, the first impedance being greater than the second impedance.

34. 33. The system of claim 32, wherein the first device comprises at least one ultrasonic transducer including a first impedance corresponding to the first frequency and a second ultrasonic transducer including a second impedance corresponding to the second frequency, the first impedance being greater than the second impedance.

35. 24. The system of claim 23, wherein the interrogation signal comprises a broad ultrasound beam.

36. 36. The system of claim 35, wherein the first device comprises an ultrasound transducer, and wherein the diameter of the wide ultrasound beam upon emission from the first device comprises a diameter greater than a dimension of the ultrasound transducer.

37. 24. The system of claim 23, wherein the interrogation signal includes one or more of an identifier, a code, and a command.

38. 24. The system of claim 23, wherein the interrogation signal comprises a radio frequency (RF) signal.

39. 24. The system of claim 23, wherein the feedback signal comprises one or more analog pulses.

40. 24. The system of claim 23, wherein the feedback signal comprises one or more of an analog pulse, an acknowledgement signal, a digital first device energy state, a digital interrogation signal strength, an identification number, a code, a command, and one or more parameters of the first device, the wireless power signal, and the data signal.

41. 24. The system of claim 23, wherein the feedback signal comprises one or more ultrasonic reflection signals corresponding to the interrogation signal.

42. 24. The system of claim 23, wherein the feedback signal comprises one or more ultrasonic backscatter signals corresponding to the interrogation signal.

43. 43. The system of claim 42, wherein the first device is configured to modulate the ultrasound backscatter signal.

44. 24. The system of claim 23, wherein the first device is configured to transmit the feedback signal at one or more frequencies.

45. 45. The system of claim 44, wherein the processor is configured to identify a frequency of the transducer arrangement for transmitting one or more of wireless power and downlink data to the first device based on the feedback signal.

46. 46. ​​The system of claim 45, wherein the identified frequency of the transducer configuration corresponds to a frequency of the feedback signal at a maximum amplitude.

47. 24. The system of claim 23, wherein the feedback signal comprises periodic transmission of one or more of an analog feedback signal and a digital feedback signal.

48. 24. The system of claim 23, wherein the transducer arrangement includes one or more transducer elements configured to focus one or more of the wireless power and the wireless data onto the first device.

49. 24. The system of claim 23, wherein the transducer arrangement includes one or more transducer elements configured to beamform signals.

50. 24. The system of claim 23, wherein the transducer configuration is configured to disable a set of transducer elements of the transducer array based on a strength of the received feedback signal.

51. 24. The system of claim 23, wherein the transducer configuration is selected based on one or more of time reversal, triangulation, and intensity estimation of the feedback signal.

52. 40. The system of claim 39, wherein the transducer configuration is selected based on one or more of time reversal, triangulation, and intensity estimation of the one or more analog pulses.

53. 24. The system of claim 23, wherein the processor is configured to adjust one or more of a transmit power and a transmit duration of the transducer arrangement based on the feedback signal.

54. 24. The system of claim 23, wherein the processor is configured to monitor one or more of a time-averaged output power of the second device, a peak output power of the second device, heating of one or more of the second device and skin, heating of the first device, heating of a tissue structure, acoustic intensity in tissue, and an energy level of the second device.

55. 24. The system of claim 23, wherein the first device is configured to monitor one or more of heating of the first device and acoustic intensity incident on the first device.

56. 24. The system of claim 23, wherein the processor is configured to adjust one or more of a transmit power and a transmit duration of the transducer arrangement based on one or more of a time-averaged output power of the second device, a peak output power of the second device, heating of one or more of the second device and skin, heating of the first device, heating of a tissue structure, acoustic intensity in tissue, and an energy level of the second device.

57. 24. The system of claim 23, wherein the processor is configured to locate the first device and adjust one or more of a transmit power and a transmit duration of the transducer arrangement based on the feedback signal.

58. 40. The system of claim 39, wherein the processor is configured to locate the first device based on the one or more analog pulses and adjust one or more of a transmit power and a transmit duration of the transducer arrangement based on one or more of digital first device energy data and digital interrogation signal strength data.

59. 1. A method for exchanging wireless signals, comprising: transmitting an interrogation signal to the first device using a first sub-array of the second device; receiving a feedback signal from the first device using a second sub-array of the second device; selecting one or more transducer configurations of the second device based on the feedback signal; and exchanging one or more wireless signals with the first device using the one or more transducer arrangements of the second device during a plurality of intervals, the wireless signals including one or more of a power signal, a data signal, an interrogation signal, a feedback signal, a downlink signal, and an uplink signal.

60. 60. The method of claim 59, further comprising transmitting the feedback signal from the first device in response to one or more wireless signals received by the first device during one or more of the plurality of intervals.

61. 60. The method of claim 59, further comprising detecting one or more of: a falling edge of one or more wireless signals; and a code corresponding to one or more wireless signals received by the first device.

62. 60. The method of claim 59, wherein selecting one or more transducer configurations of the second device comprises one or more of determining one or more of frequency, delay, phase, amplitude, and gain of the selected one or more transducer elements based at least in part on one or more of delay, phase, time of arrival, time of flight, amplitude, frequency, and encoded data of the feedback signal.

63. 60. The method of claim 59, further comprising determining to transmit one or more of a power signal, an interrogation signal, a data signal, and a downlink signal to the first device in response to the received feedback signal.

64. 60. The method of claim 59, further comprising determining to inhibit transmitting the wireless signal to the first device in response to the received feedback signal.

65. 60. The method of claim 59, wherein the transducer configuration corresponding to the subsequent interval is selected based on one or more previously received feedback signals during one or more previous intervals.

66. 60. The method of claim 59, wherein the duration of at least one interval of the plurality of intervals is determined by the first device.

67. 60. The method of claim 59, wherein the duration of at least one interval of the plurality of intervals is determined by the second device.

68. 60. The method of claim 59, wherein the first device is configured to periodically transmit the feedback signal during one or more of the intervals.

69. 60. The method of claim 59, wherein the one or more transducer configurations are selected based on time reversal.

70. 70. The method of claim 69, further comprising identifying a frequency of a feedback signal, wherein the one or more transducer configurations include the identified frequency.

71. 70. The method of claim 69, further comprising identifying a frequency of the feedback signal, wherein the one or more transducer configurations include a frequency different from the identified frequency.

72. 60. The method of claim 59, wherein selecting one or more transducer configurations of the second device includes estimating a set of spatial coordinates of the first device using triangulation, and wherein exchanging one or more of the wireless power signals and the wireless data signals using the one or more transducer configurations is based at least in part on the estimated spatial coordinates.

73. 60. The method of claim 59, wherein the first subarray and the second subarray include the same transducer elements.

74. Selecting one or more of the transducer configurations of the second device comprises: estimating the strength of the feedback signal received by the second sub-array of the second device; and and exchanging one or more of the wireless power and data signals using the one or more transducer arrangements based on the estimated strength of the received feedback signal.

75. 60. The method of claim 59, wherein the feedback signal comprises a digital amplitude of the interrogation signal received by the first device, and wherein selecting the one or more transducer configurations of the second device comprises selecting one or more of the sub-arrays corresponding to a maximum digital amplitude of the interrogation signal.

76. the feedback signal comprises a first feedback signal, and the method further comprises: powering the first device by transmitting a first power signal during a first power interval; 60. The method of claim 59, further comprising receiving a second feedback signal from the first device after the first power interval.

77. 60. The method of claim 59, further comprising intermittently powering the primary device, the secondary device being configured to inhibit powering of the primary device based on the feedback signal.

78. 78. The method of claim 77, wherein the interrogation signal is a first interrogation signal, and further comprising transmitting a second interrogation signal to the first device after a time delay.

79. 78. The method of claim 77, further comprising receiving a second feedback signal from the first device after a time delay.

80. 80. The method of claim 79, wherein the first device is configured to transmit the feedback signal after a time delay.

81. 60. The method of claim 59, further comprising selecting the transducer configuration based on a location of the first device.

82. 82. The method of claim 81, further comprising storing the transducer configuration corresponding to the location of the first device in a memory of the second device.

83. 83. The method of claim 82, further comprising selecting the stored transducer configuration for exchanging one or more of the wireless power signal and the wireless data signal with the first device.

84. 60. The method of claim 59, wherein the duration of the interval is predetermined.

85. 60. The method of claim 59, wherein the first device is configured to transmit a plurality of feedback signals upon receipt of the interrogation signal.

86. 86. The method of claim 85, wherein the plurality of feedback signals comprises pulses periodically transmitted by the first device.

87. 86. The method of claim 85, further comprising estimating a spatial path of the first device based on the plurality of feedback signals.

88. 88. The method of claim 87, further comprising selecting the transducer configuration that corresponds to the spatial path of the first device based on the estimated spatial path.

89. 60. The method of claim 59, further comprising generating a location notification corresponding to a spatial adjustment of the second device.

90. 90. The method of claim 89, wherein generating the location notification is based on an estimated spatial path of the first device.

91. 91. The method of claim 90, wherein spatial adjustment comprises aligning an axis of the second device with the spatial path of the first device.

92. 92. The method of claim 91, wherein the second device comprises a one-dimensional linear ultrasound transducer array, and the spatial adjustment comprises aligning one or more of an aperture and an elevation angle of the array with the spatial path of the first device.

93. 90. The method of claim 89, wherein the location notification is based on a position of the transducer arrangement relative to one or more of a center, an edge, and a predetermined location of the second device.

94. 90. The method of claim 89, wherein generating the location notification is based on the feedback signal.

95. 60. The method of claim 59, comprising generating a power notification comprising a power state of one or more of the first device and the second device.

96. 60. The method of claim 59, comprising generating a communication notification corresponding to one or more of the data received from the first device, physiological parameter data, and parameter data of one or more of the first and second devices.

97. 1. A system comprising: a first device comprising a plurality of transducers configured to receive downlink signals; a second device configured to transmit the downlink signal, wherein one or more of the plurality of transducers are configured to exchange one or more of wireless power and wireless data with the second device based on the received downlink signal.

98. 98. The system of claim 97, wherein the first device comprises an implantable medical device and the second device is configured to be placed external to the patient's body.

99. 98. The system of claim 97, wherein the plurality of transducers comprises a plurality of ultrasound transducers.

100. 98. The system of claim 97, further comprising a power circuit configured to DC-couple the received power.

101. 98. The system of claim 97, wherein the downlink signals include one or more of an interrogation signal, a power signal, and downlink data.

102. 98. The system of claim 97, wherein one or more of the plurality of transducers of the first device are configured to exchange wireless data with the second device at a first frequency that is different from a second frequency of the received wireless power.

103. 98. The system of claim 97, wherein the first device further comprises a processor.

104. 104. The system of claim 103, wherein the processor is configured to select one or more of the plurality of transducers configured to exchange one or more of the wireless power and the wireless data with the second device based on the received downlink signal.

105. 105. The system of claim 104, wherein the processor is configured to periodically update the selection based on one or more of the received downlink signals.

106. 104. The system of claim 103, wherein the processor is configured to calculate received signal strengths of the downlink signals for one or more of the plurality of transducers and compare the received signal strengths of one or more of the plurality of transducers with each other.

107. 107. The system of claim 106, wherein the processor is configured to select one or more of the plurality of transducers corresponding to the received signal strength above a predetermined threshold for exchanging one or more of the wireless power and the wireless data with the second device.

108. 107. The system of claim 106, wherein the processor is configured to select one transducer corresponding to a maximum received signal strength for transmitting an uplink signal to the second device.

109. 104. The system of claim 103, wherein the processor is configured to decode one or more downlink commands based on the downlink signal.

110. 110. The system of claim 109, wherein the processor is configured to select one or more transducers for exchanging one or more of the wireless power and the wireless data with the second device based on decoding of one or more of the downlink commands.

111. 1. A system comprising: a first device configured to transmit an interrogation signal through a transmission medium, the interrogation signal in the transmission medium configured to generate a reflected interrogation signal; a second device configured to receive the interrogation signal from the first device and to transmit a feedback signal including at least one parameter different from the reflected interrogation signal.

112. 112. The system of claim 111, wherein the first device is configured to be placed external to a patient's body and the second device comprises an implantable medical device.

113. 112. The system of claim 111, wherein the at least one parameter comprises one or more of amplitude, signal strength, phase, frequency, time delay, and signal modulation.

114. 112. The system of claim 111, wherein the second device is configured to transmit a feedback signal using one or more of active signal transmission and backscatter modulation.

115. 112. The system of claim 111, wherein the at least one parameter includes a time delay, and the second device is configured to transmit the feedback signal after receiving the interrogation signal and the time delay.

116. 116. The system of claim 115, wherein the time delay is at least about 10 microseconds.

117. 112. The system of claim 111, wherein the interrogation signal includes a first modulation and the feedback signal includes a second modulation different from the first modulation.

118. 112. The system of claim 111, wherein the interrogation signal comprises an ultrasonic signal and the feedback signal comprises a radio frequency signal.

119. 112. The system of claim 111, wherein the interrogation signal comprises a radio frequency signal and the feedback signal comprises an ultrasonic signal.

120. 112. The system of claim 111, wherein the feedback signal includes one or more of a code and a waveform characteristic that differs from one or more of the reflected interrogation signals.

121. 1. A method for positioning a wireless device on a body, comprising: generating a user prompt corresponding to a desired location on the body; and directing the wireless device according to one or more of an orientation feature and an orientation signal of the wireless device.

122. 122. The method of claim 121, wherein providing the user prompt includes one or more of a body location image, a visual indication, and an audio indication.

123. 122. The method of claim 121, wherein the orientation feature of the wireless device comprises one or more of a marking, a structure, and a shape of the wireless device.

124. 122. The method of claim 121, wherein the orientation signal of the wireless device includes a signal from one or more of a direction sensor, an accelerometer, a gyroscope, and a position sensor.

125. 1. A method for positioning a wireless device on a body, comprising: measuring one or more parameters of the wireless device and the body; estimating a position of the wireless device on the body based on the measured parameters; generating a user prompt corresponding to the estimated location of the wireless device on the body.

126. 126. The method of claim 125, wherein the parameters include one or more of heart sounds, lung sounds, respiratory sounds, wireless signals coming from an implantable medical device, and wireless reflected signals.

127. 126. The method of claim 125, wherein the user prompt includes one or more of: a notification regarding the estimated location of the wireless device on the body; and a recommendation including one or more of repositioning the wireless device on the body and contacting a medical professional.

128. 128. The method of claim 127, wherein repositioning the wireless device on the body includes one or more of moving, adjusting, and rotating the wireless device.

129. 1. A method of coupling an ultrasound device to a patient's body, comprising: measuring one or more parameters of the ultrasound device and the body; estimating a coupling condition between the ultrasound device and the body based on the measured parameters; generating a user prompt corresponding to the coupling condition between the ultrasound device and the body.

130. 130. The method of claim 129, wherein the ultrasound device includes one or more ultrasound transducers.

131. 131. The method of claim 130, wherein the parameters include one or more of the electrical impedance of the ultrasound transducer, the reflection coefficient of the ultrasound transducer, heart sounds, lung sounds, ultrasound signals transmitted from an implantable medical device, ultrasound reflected signals, pressure, force, contact, capacitance, electrical impedance of tissue, heat, and temperature.

132. 130. The method of claim 129, wherein estimating the coupling state includes estimating one or more of the adequacy and degree of coupling between the ultrasound device and the body.

133. 130. The method of claim 129, wherein the user prompts include one or more of the coupling status and recommendations including one or more of repositioning the ultrasound device relative to the body, applying an ultrasound coupling agent, adjusting fasteners of the ultrasound device relative to the body, and contacting a medical professional.

134. 130. The method of claim 129, further comprising periodically transmitting uplink signals from an implantable medical device, and wherein estimating the coupling state is based on measuring the strength of one or more of the uplink signals received by the ultrasound device.

135. 130. The method of claim 129, further comprising transmitting an interrogation signal from the ultrasound device and receiving one or more feedback signals from an implantable medical device, wherein estimating the coupling state is based on measuring the strength of one or more of the feedback signals received by the ultrasound device.

136. 1. A method for reducing noise, comprising: measuring a parameter of the ultrasonic signal received by one or more of an ultrasonic transducer, a pressure transducer, a flow sensor, a force sensor, and a MEMS device; generating pressure data based on the pressure signal measured by the pressure transducer and the measured parameter of the ultrasonic signal.

137. 137. The method of claim 136, wherein generating the pressure data includes separating the ultrasound signal from the pressure signal.

138. 138. The method of claim 137, wherein separating the ultrasonic signal from the pressure signal includes one or more of averaging, digital signal processing, and analog signal processing.

139. generating the pressure data, identifying one or more pressure samples of the pressure data including the measured parameter of the ultrasound signal; and rejecting or flagging the identified one or more pressure samples.

140. 140. The method of claim 139, further comprising measuring a pressure signal using the pressure transducer after a time delay.

141. 141. The method of claim 140, wherein the time delay is predetermined.

142. 141. The method of claim 140, wherein the time delay is determined based on dissipation of the ultrasound signal.

143. 137. The method of claim 136, wherein generating the pressure data is performed by a processor of a first device comprising the ultrasound transducer and the pressure transducer.

144. 137. The method of claim 136, wherein generating the pressure data is performed by a processor of a second device in wireless communication with a first device comprising the ultrasound transducer and the pressure transducer.

145. 1. A method for reducing noise, comprising: receiving an ultrasonic signal using a pressure transducer of the device; filtering the ultrasonic signal using a filter coupled to the pressure transducer.

146. 146. The method of claim 145, wherein filtering the ultrasound signal includes one or more of analog filtering, digital filtering, analog post-processing, digital post-processing, and the use of one or more of an amplifier, a processor, an integrator, an averager, and a boxcar sampler.

147. 1. A method for estimating a heart rate, comprising: measuring a blood pressure sample using a first device; generating blood pressure data using the measured blood pressure samples; and using the blood pressure data to estimate heart rate over one or more cardiac cycles.

148. 148. The method of claim 147, wherein the first device comprises an implantable device.

149. 148. The method of claim 147, wherein estimating the heart rate is performed by a processor of the first device.

150. 148. The method of claim 147, wherein estimating the heart rate is performed by a processor of a second device, the second device being in wireless communication with the first device.

151. estimating the heart rate comparing one or more of the blood pressure samples to a predetermined threshold; identifying two or more crossing points at which the blood pressure samples cross the predetermined threshold; and estimating a heart rate based on one or more elapsed times between the identified intersections.

152. estimating the heart rate identifying a maxima or minima of the blood pressure samples; and estimating the heart rate based on one or more elapsed times between two or more local maxima or minima.

153. estimating the heart rate identifying a maximum rate of change point or a minimum rate of change point of said blood pressure samples; and estimating the heart rate based on one or more elapsed times between two or more of the maximum or minimum rate of change points.

154. 148. The method of claim 147, wherein estimating the heart rate is based on a frequency domain representation of the blood pressure samples.

155. 1. A system configured to exchange wireless power or wireless data, comprising: a first device configured to traverse a spatial pathway within a patient; a second device configured to exchange wireless signals with the first device only during an access period.

156. The first device or the second device a sensor configured to measure one or more physiological parameters of the patient; and a processor configured to identify the access period based on the one or more measured physiological parameters.

157. 157. The system of claim 156, wherein the one or more physiological parameters include one or more of blood pressure, heart rate, respiratory rate, heart sounds, lung sounds, and ECG.

158. 1. A method of parameter tracking, comprising: Tracking one or more parameters corresponding to a wireless system comprising a first device and a second device; selecting a transducer configuration for the second device based at least in part on the parameters; exchanging one or more wireless signals with the first device using the selected transducer configuration.

159. 159. The method of claim 158, wherein the parameters include one or more of a wireless link gain between the first device and the second device, a transmit power of the second device, a transmit frequency of the second device, one or more parameters of the transducer configuration, one or more parameters of the first device, an energy state of the first device, a battery life of the first device, a parameter corresponding to a sensor of the first device, a parameter corresponding to a transducer of the first device, a transmit frequency of the first device, a transmit power of the first device, one or more positions of the first device, one or more orientations of the first device, and a physiological parameter of the body.

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