Wireless sensor reader with multiple fixed excitation frequencies

Abstract

A wireless sensor reader configured to determine the resonant frequency of a sensor may include a transmitting circuit configured to transmit a wireless biasing pulse to the sensor at a transmitting frequency, thereby exciting a resonant circuit within the sensor and causing it to resonate at a frequency proportional to the measurement parameter, and a receiving circuit configured to receive a response signal from the sensor, which is a continuous wave at the sensor's resonant frequency. The wireless sensor reader may also include a circuit for determining the frequency of the sensor's response signal, in which case the reader selects the transmission frequency of the biasing pulse from a plurality of distinct narrowband frequencies, and this selection is made before determining the frequency of the sensor's response signal.

Description

[Technical Field]

[0001] Cross-references to related applications This application was filed on 23 May 2023 and claims priority to U.S. Provisional Patent Application No. 63 / 468,354, entitled “WIRELESS SENSOR READER WITH MULTIPLE FIXED EXCITATION FREQUENCIES,” which is incorporated herein by reference in its entirety.

[0002] Technical field This disclosure generally relates to wireless sensor systems, and more specifically to wireless sensor systems in which a sensor is read by a reader, in which case the sensor is an LC resonant tank circuit, the reader wirelessly excites and resonates the sensor, receives the reflected response signal and identifies its frequency, which has a known relationship with the physical parameter being measured. [Background technology]

[0003] Wireless sensor systems may utilize resonant circuit technology, employing passive wireless sensors that communicate remotely with excitation and reader circuits. Often, wireless sensors are implanted in specific locations, such as within the human body, to detect and transmit detection parameters. In some systems, the detection parameters alter the resonant frequency of the wireless sensor. The reader may detect the resonant frequency of the wireless sensor to identify (determine) the detection parameters.

[0004] In one application, passive wireless sensor systems may utilize resonant circuit technology. Passive wireless sensor systems may be pressure monitoring devices for use by themselves or incorporated into other medical devices, including, but not limited to, pacemakers, defibrillators, drug dissolution devices, and ventricular assist devices (VADs). In one embodiment, a medical device may include one or more sensors configured to be positioned at a desired location within the human body. One or more sensors may be manufactured using microelectromechanical systems (MEMS) technology and configured to transmit wireless data to an external receiver or reader, for example, facilitating the transmission of diagnostic health data to a physician, clinician, nurse, patient caregiver, or patient.

[0005] One such sensor, formed using MEMS technology, has inductive and capacitive components. For example, the sensor includes an inductor (L) and a capacitor (C) connected in parallel, commonly known as an LC tank circuit. The geometric shape of the sensor allows the capacitive plate to deform as the pressure increases. This deformation leads to plate deflection, which in turn causes a change in the system's capacitance value. The LC tank circuit also generates an electronic resonant frequency. This resonant frequency is related to the inductance (inductive) and capacitance values ​​of the circuit and changes along with the deflection of the capacitor plate in response to pressure changes. This emitted resonant frequency signal is received by an external wireless receiver or reader and decoded into correlated pressure measurements.

[0006] Furthermore, such sensors may also include wireless data transmission capabilities. The device may not require a battery or internal power source. Rather, the sensor may be powered by an inductively coupled electromagnetic (EM) field directed towards its inductor coil. A receiver or reader may provide the electromagnetic field by generating radio frequency (RF) bursts or other signals. The sensor's inductor receives energy from the EM field and stores it by resonating the sensor's LC tank. When the external EM field is removed, the inductance and capacitance form a parallel resonant circuit, radiating energy through the inductor acting as an antenna. This oscillating circuit then generates an RF signal whose frequency is proportional to the sensor's capacitance value, which changes with pressure. The sensor's inductor coil may function as an inductor that generates an oscillating RF signal with a frequency proportional to the sensor's capacitance at a specific pressure, and as an antenna coil that radiates the RF signal generated by the LC tank circuit to provide the reader with an oscillating RF signal.

[0007] The pressure sensor may include an inductor / capacitor circuit assembled in a parallel configuration. In other embodiments, it may include a piezoelectric, piezoresistive, or capacitive pressure sensor. In the inductor / capacitor circuit, the resonant frequency of the biased circuit changes with the patient's internal pressure. The sensor wirelessly transmits the detected or measured pressure measurement to an external system receiver via an RF signal, without requiring an internal power supply system. In certain embodiments, the sensor may be biased via an electromagnetic field directed towards the sensor's circuitry.

[0008] Wireless sensor readers, intended for more frequent use by home healthcare patients, are particularly useful for measuring internal parameters of interest to caregivers. However, to ensure patient compliance when performing these measurements consistently and accurately, the functionality of this system, especially the reader's functionality and usability, needs to be improved. Furthermore, functionality, accuracy, and secure data management must be ensured to allow users to easily integrate the reader and related systems into their daily lives and to improve the reliability of the reader in the field.

[0009] Other prior arts propose sweep frequency systems to achieve the same objective. In these systems, different transmission frequencies f xmt Multiple excitation pulses having are sent from the reader to the sensor, and any change in the system parameters is reflected in the previous f of those parameters. xmt Observed relative to a value. The changed parameter may be the power supplied to the sensor by the reader, the amplitude or phase of the sensor response or "ringback" signal, or some other parameter. If the changed parameter is at or near its maximum or minimum value, the sensor is assumed to be at its resonant frequency. The excitation frequency f used to elicit the response at sensor resonance. xmt This is assumed to coincide with the sensor's resonant frequency, and the measured physical parameters can be derived at this point.

[0010] U.S. Patent Application Publication No. 2023 / 0072070, incorporated herein by reference in its entirety, details a method and system for performing this measurement. However, that method and system does not use the sweep frequency scheme described above. Rather, even before the start of the reading, a single excitation frequency f xmt The excitation frequency is pre-selected. The excitation frequency is used to excite the sensor to resonate, and then it is suddenly switched off. The sensor is f xmtSignal strength, the physical distance between the reader and the sensor antenna (referred to as the "link distance"), the RF quality factor (Q value) of the transmitted signal and the sensor, and f xmt and the resonant frequency f of the sensor res and continues to resonate over time determined by the difference (delta) between and the resonant frequency f of the sensor. When resonating, the sensor transmits a response signal, or "ringback" signal, which can be received by the reader. The ringback signal can only resonate at f res and is generally weak and rapidly decays to zero. The reader must identify f res before the response signal disappears. This "fixed frequency" transmission method is superior to the "swept frequency" method. Its circuit is generally smaller and lower power, facilitating the design of handheld readers. Its control algorithm is generally simpler and less prone to false locking to radiators other than nearby sensors or its own sideband frequencies.

[0011] However, the fixed frequency method has its own limitations. When the excitation frequency f xmt is equal to the resonant frequency f of the sensor, the resonator of the sensor accumulates the maximum RF energy, and the response signal reflected to the reader has a high signal strength (SS), providing the reader with a high signal-to-noise ratio and a longer duration response signal, enabling more accurate phase or frequency measurements. As f res moves away from f xmt the response signal strength of the sensor rapidly weakens. At a specific delta between f res and f xmt the sensor response signal is too weak for the reader to detect. Therefore, in order to perform more accurate phase or frequency measurements, the excitation signal frequency f of the reader res must always be close enough to the sensor f xmt to draw a signal that exceeds the minimum signal strength (power amplitude) detection threshold of the reader. res Such a design may impose other limitations on the system. The sensor is at f

[0012] This design may impose other limitations on the system. The sensor is at f resIts full-scale operating range must be designed to be narrow enough so that it always falls within a specific bandwidth, in which case the bandwidth is the f of the leader. xmt It is centered on f. xmt A fixed-frequency reader of =13.5MHz may be used with a sensor with an operating bandwidth of 13-14MHz, which corresponds inversely proportional to the pressure measurement range of 550-900mmHg, as can be seen on the x-axis in Figure 1. The dotted arrow in the center indicates f xmt = This is the narrowband excitation signal of the leader at 13.5 MHz. The bell-shaped curve represents the transfer function of the sensor, which shows the sensor's response intensity to its excitation signal at different frequencies. When the measured pressure is 737 mmHg, the sensor responds to f as seen by the solid arrow just to the left of the central arrow. res It resonates at =13.462MHz. The amplitude of this arrow is high, as shown by the sensor's response curve, indicating a strong response signal far above the reader's detection threshold, which is shown as a dotted horizontal line crossing the graph. In another measurement, with a pressure of 689mmHg, f res This becomes 13.602MHz, and to the right of the center, f xmt Located slightly away from the center, this signal may be slightly less accurate, but it is still strong enough to be detected. When the pressure is far from the center, for example at 870 mmHg, f res This results in a frequency of 13.120MHz, which is too weak for the reader to detect.

[0013] The exemplary fixed-frequency system in Figure 1 has a limited operating measurement range, which is confined to the space between two points where the sensor response curve intersects the reader detection threshold line (approximately 673–778 mmHg in this example). Designing LC resonant tank microsensors with a wider operating range generally suffers undesirable disadvantages in terms of size, precision, accuracy, and manufacturability. Thus, a fixed f xmt Maintaining the advantages of the architecture, and extending the sensor frequency f over a wider operating bandwidth. res A wireless LC resonant tank sensor-reader system is needed to enable detection of [the specified element].

[0014] overview The following provides an overview of the Disclosure and a basic understanding of several embodiments. This overview is not intended to identify any major or significant elements or to define any limitations on the embodiments or claims. Furthermore, this overview may provide a simplified overview of several embodiments that may be described in more detail in other parts of the Disclosure. Any embodiments described may be separated or combined without limitation with other described embodiments to have the same effect as if they were described individually and in any possible combination.

[0015] A wireless sensor reader is disclosed configured to determine the resonant frequency of a sensor, which may include a transmitting circuit configured to transmit a wireless biasing pulse to the sensor at a transmitting frequency to excite a resonant circuit within the sensor to resonate at a frequency proportional to a measurement parameter, and a receiving circuit configured to receive a response signal from the sensor, which is a continuous wave at the sensor's resonant frequency. The wireless sensor reader may also include a circuit for determining the frequency of the sensor's response signal, in which the reader selects a transmitting frequency for the biasing pulse from a plurality of distinct narrowband frequencies, the selection made before determining the frequency of the sensor's response signal, the reader takes a plurality of samples of the sensor's response signal over a measurement time interval, the frequency of each of the plurality of samples of the sensor's response signal is determined by the frequency determining circuit, and each of the plurality of samples of the sensor's response signal is started by a biasing pulse of the same transmitting frequency over the entire measurement time interval.

[0016] The devices, systems, and methods described may provide LC resonant tank sensors and microsensors with a wider operating range without undesirable disadvantages in size, precision, accuracy, and manufacturability. The devices, systems, and methods described may provide fixed f xmt While maintaining the advantages of the architecture, sensor frequency f over a wide operating bandwidth.res We may provide a wireless LC resonant tank sensor-reader system that enables detection of [unclear / unclear].

[0017] A wireless sensor reader configured to determine the resonant frequency of a sensor is disclosed. In one embodiment, the reader may include a transmitting circuit configured to transmit a wireless biasing pulse to the sensor at a transmitting frequency, thereby exciting a resonant circuit within the sensor to resonate at a frequency proportional to a measurement parameter. In one embodiment, the reader may include a receiving circuit configured to receive a response signal from the sensor, which is a continuous wave at the sensor's resonant frequency. In one embodiment, the reader may include a circuit for determining the frequency of the sensor's response signal.

[0018] In one embodiment, the reader may select the transmission frequency of the biasing pulse from a plurality of distinct narrowband frequencies. In one embodiment, this selection may be made before determining the frequency of the sensor's response signal. In one embodiment, the reader may acquire a plurality of samples of the sensor's response signal over a measurement time interval. In one embodiment, the frequency of each of the plurality of samples of the sensor's response signal may be determined by a circuit for determining the frequency. In one embodiment, each of the plurality of samples of the sensor's response signal may be initiated by a biasing pulse of the same transmission frequency over the entire measurement time interval.

[0019] In one embodiment, the circuit for determining the frequency of the sensor response signal may include a phase-locked loop configured to lock an internal continuous wave signal to the response signal before the response signal decays, such that the frequency of the internal signal matches the frequency of the sensor response signal. In one embodiment, the phase-locked loop may be further configured to hold the internal signal at a constant frequency before the response signal decays. In one embodiment, the constant frequency of the internal signal may be equal to the frequency of the sensor response signal. In one embodiment, the reader may further include a circuit for determining the frequency of the held internal signal while it is held at a constant frequency. In one embodiment, the circuit for determining the frequency of the held internal signal may be configured to measure the elapsed time of a period of the internal signal.

[0020] In one embodiment, the selection of the transmission frequency of the biasing pulse may be performed before the frequency of the sensor's response signal is determined. In one embodiment, the reader may be further configured to use previously measured data to select the first transmission frequency of the biasing pulse at the start of the measurement time interval. In one embodiment, the previously measured data may be selected from ambient pressure, historical measurements of the mean of reference pulmonary artery pressure, or calculation results using these parameters.

[0021] In one embodiment, the reader may be further configured to measure the signal intensity of the sensor's response signal. In one embodiment, the reader may be further configured to determine whether the measured signal intensity falls within a preset threshold window. In one embodiment, the window may have a lower limit that determines the minimum signal intensity required for frequency detection by the reader, and an upper limit that determines the maximum signal intensity that allows for preventing saturation of the receiving circuit. In one embodiment, the reader may be further configured to provide the user with an audible, visual, or tactile cue indicating whether the sensor's response signal intensity falls within the window. In one embodiment, the reader may be further configured to select the transmission frequency by transmitting a plurality of excitation pulses, each having a different frequency selected from the plurality of distinct narrowband frequencies, the selection of the transmission frequency based on the signal intensity of the sensor's response signal for each of the excitation pulses.

[0022] In one embodiment, the reader may be further configured to repeat a portion of the process of selecting a transmit frequency if two or more of the plurality of distinct narrowband frequencies produce a sensor response signal that saturates the receiving circuit. In one embodiment, the repeated portion may include repeating the step of the user repositioning the reader in response to the tactile cue. In one embodiment, the reader may be further configured to use the previously measured data to exclude the selection of a transmit frequency from the plurality of distinct narrowband frequencies if the transmit frequency cannot be the frequency closest to the sensor's resonant frequency. In one embodiment, the reader may record data during each reading interval so that future reading intervals include the previously measured data.

[0023] In one embodiment, the reader may be further configured to analyze the sample of the sensor's response signal over a portion of the measurement time interval to determine whether the frequency of the sample has approached another frequency of the plurality of distinct narrowband frequencies compared to the current excitation signal frequency. In one embodiment, the reader may be further configured to change the current excitation signal frequency to another frequency of the plurality of distinct narrowband frequencies for the remainder of the measurement time interval. In one embodiment, the plurality of distinct narrowband frequencies may be spaced along a frequency spectrum over the full-scale range of the sensor's resonant frequencies.

[0024] In one embodiment, the transfer functions of the sensor with respect to adjacent distinct narrowband frequencies on the frequency spectrum may partially overlap with each other, ensuring that the sensor's response signal at each frequency in the full-scale range of the sensor's resonant frequency has at least one reader transmit frequency that can excite the sensor to supply the reader with a sensor response signal of sufficient energy to identify the frequency of the response signal. In one embodiment, the reader may be further configured to select an excitation signal transmit frequency from among the adjacent frequencies if the intensity of the response signal is equal with respect to two adjacent frequencies. In one embodiment, the selection of the excitation signal transmit frequency may be performed by an algorithm selected from a group including: selecting the transmit frequency closest to the expected sensor resonant frequency based on measurement parameters; selecting the transmit frequency based on past measurements of the sensor's resonant frequency; selecting the transmit frequency closest to the center of the full-scale range; selecting the transmit frequency most frequently used in past measurements; selecting the transmit frequency based on data from the patient's medical history; and selecting the transmit frequency based on the patient's posture as measured by the reader's tilt sensor.

[0025] In one embodiment, the plurality of samples of the sensor's response signal over a measurement time signal may include output waveforms of measurement parameters. In one embodiment, the plurality of samples of the sensor's response signal may be processed to obtain output parameters, the processing of the samples being selected from averaging, low-pass filtering, band-pass filtering, weighted averaging, moving window averaging, Fourier transform, wavelet transform, differentiation, integration, curve fitting, calculation of area under the curve, trend analysis, correlation with other datasets, standard deviation, analysis of variance, minimum and maximum detection, rise and fall times, or other mathematical data processing (processes). In one embodiment, the resonant frequency of the sensor may be proportional to cardiac pressure, and the processing of the samples being further selected from heart rate detection, respiratory rate detection, systolic peak detection, diastolic minimum detection, cardiac output estimation, flow rate estimation, arrhythmia detection, irregular breathing detection, vascular compliance estimation, patient posture, patient activity level, patient health status, and comparison of any of these parameters with a predetermined threshold. In one embodiment, the patient's health status may include one or more of the following: vital signs, comorbidities, medications, age, and weight.

[0026] In one embodiment, the reader may be further configured to calculate the rate of change of the sensor's resonant frequency during the measurement time interval and to automatically switch the excitation transmission frequency to the new value if the rate of change indicates that the sensor's resonant frequency is likely to remain closer to the new value during the remainder of the time interval. In one embodiment, the sensor's resonant frequency may be proportional to cardiac pressure. In one embodiment, the automatic switching of the excitation frequency may occur each time the cardiac pressure approaches its maximum systolic or minimum diastolic value. In one embodiment, the circuit for determining the frequency may determine it independently of the transmission frequency of the biasing pulse.

[0027] The following description and drawings disclose various exemplary embodiments. While some improvements and novel embodiments may be explicitly identified, other embodiments may be apparent from the description and drawings.

[0028] The object, advantages, and operation of the present invention can be better understood by referring to the following detailed description made in conjunction with the following drawings. [Brief explanation of the drawing]

[0029] [Figure 1] This graph shows the sensor response curve of the conventional technology intersecting the reader detection threshold line.

[0030] [Figure 2] The graph shows fixed 4-band transmit and sensor response curves that identify frequency and pressure.

[0031] [Figure 3] This is a flowchart of the control algorithm for fixed-frequency transmission.

[0032] [Figure 4] This is one embodiment of a wireless sensor system.

[0033] The present invention can be embodied in various forms without departing from its spirit or essential features. The scope of the present invention is defined in the appended claims and not in any particular description preceding them. Accordingly, all embodiments that fall within the meaning and scope of the claims and their equivalents are intended to be encompassed by the claims.

[0034] Detailed explanation Now, let us refer in detail to the exemplary embodiments of this instruction, which are shown in the accompanying drawings, where identically numbered embodiments refer to features common throughout. It should be understood that other embodiments may be used without departing from the individual scope of this instruction, and structural and functional modifications may be made. Furthermore, features of various embodiments may be combined or modified without departing from the scope of this instruction. Accordingly, the following description is presented for illustrative purposes only and should not in any way limit the various alternatives and modifications that may be made to the illustrated embodiments, which remain within the spirit and scope of this instruction.

[0035] In this disclosure, numerous specific details provide a complete understanding of the disclosure. It should be understood that aspects of this disclosure may be implemented in other embodiments, which do not necessarily include all aspects described herein.

[0036] As used herein, the words “example” and “exemplary” mean actual examples or illustrations. The words “example” or “exemplary” do not indicate important or preferred modes or embodiments. The word “or” is intended to be inclusive, not exclusive, unless specifically indicated by the context. For example, the phrase “A uses B or C” includes any inclusive substitution (e.g., A uses B; A uses C; or A uses both B and C). Separately, the articles “a” and “an” are generally intended to mean “one or more” unless specifically indicated by the context.

[0037] A wireless sensor reader is disclosed. In one embodiment, the wireless sensor reader may be configured to determine the resonant frequency of a sensor and may include a transmitting circuit configured to transmit a wireless biasing pulse to the sensor at a transmitting frequency to excite a resonant circuit within the sensor to resonate at a frequency proportional to a measurement parameter, and a receiving circuit configured to receive a response signal from the sensor, in which case the response signal is a continuous wave at the sensor resonant frequency.

[0038] Furthermore, the wireless sensor reader may also include a circuit for determining the frequency of the sensor response signal, in which case the reader selects a transmission frequency for the biasing pulse from a plurality of separate narrowband frequencies, and this selection is made before determining the frequency of the sensor response signal. The reader then acquires multiple samples of the sensor response signal over a measurement time interval, the frequency of each of these samples is determined by the circuit for determining that frequency, and each of these samples is started with a biasing pulse of the same transmission frequency throughout the entire measurement time interval.

[0039] Wireless sensor systems may generally include a reader unit or reader device configured to be in an operational state for taking readings from the sensor and in a dormant state when not communicating with the sensor. For example, the disclosed reader may be handheld or battery-powered and adapted to operate for a few minutes each day for use. For example, the disclosed reader may be handheld or battery-powered and adapted for use to operate for separate periods or preset periods, including during certain physical activities such as exercise, walking, and cycling. For example, the disclosed reader may be handheld or battery-powered and adapted for use to operate during exercise. The reader may be programmed to dynamically change the Tx band as needed during a walking test (e.g., a 9-minute walk test). The disclosed reader may also be configured to be placed in a refill station or docking station when not in use. It should be noted that the disclosed sensor and reader systems may incorporate many types of wireless technologies, including, for example, active and passive sensors, continuous wave (CW) and modulated data transmission, and analog and digital type systems.

[0040] Figure 2 illustrates the operational concept of this system using exemplary parameter values. Here, the reader is designed to transmit excitation pulses at multiple distinct narrowband fixed frequencies (four in this example). Note that the transmission bandwidth and f are 2, 3, 4, 5, 6, 7, 8, 9, 10, or more. xmt Any number of transmission bandwidths (bands), including frequencies, can be used. In one example, the leader may use two or more, three or more, multiple, or more transmission bandwidths and f xmt In some cases, frequencies are transmitted. The four f's shown in Figure 2 xmt Each frequency is located at the center of the frequency spectrum "band" (bands labeled A through D). res This depends on the value of the parameter being measured (pressure in this example) and can be anywhere on the 13-14 MHz spectrum shown, or in other embodiments, it may be on an alternative spectrum (e.g., 15-16 MHz, 11-12 MHz, 12-13 MHz, or 14-15 MHz). Now, this leader is f res The closest f xmt Select a band with a value to optimize energy transfer to the sensor during excitation, f res It provides a strong, long-lasting ringback signal to facilitate measurement and can be used when measuring pressure at the sensor's location, such as in the pulmonary artery.

[0041] From Figure 2, it can be seen that every frequency in the sensor's full-scale range spectrum has at least one band where the transfer function exceeds the reader detection threshold. As illustrated, adjacent bands partially overlap, providing an intermediate region between two adjacent transmission frequencies, in this case either f xmt However, this excites the sensor, producing equal or nearly equal ringback response intensities. In actual field use, factors such as environmental noise, reader position, and manufacturing tolerances can cause asymmetry, resulting in one of the partially overlapping bands providing a better signal intensity to the sensor's return signal than the other.

[0042] If the return signal strength (SS) between adjacent bands is equal or nearly equal, the system, according to the algorithm, determines one or the other band and its corresponding f xmt Select the following. The algorithm may include the following, namely, ·P amb Estimated f based on res The closest f xmt Select this option, with or without the mean pulmonary artery pressure (mPAP) offset from past measurements; • Select the band closest to the center of the entire bandwidth; • Select a band based on past data (a band that has been frequently used in the past).

[0043] Figure 3 shows the optimal f to select for a given reading from a number of distinct frequencies available. xmt The algorithm used by the leader to determine this is illustrated in Figure 3. The example shown consists of a 20-second reading from an LC resonant tank pressure sensor located in the patient's pulmonary artery. The details of the application and the parameter values ​​provided are merely examples and can be substituted with other values ​​without modifying the system.

[0044] In step 1, starting from the top left or "Start", the reader selects its separate transmission frequency f used for sensor excitation. xmt Select the first one. Generally, this value is the current f of the sensor. res The selection is based on a rough estimate of the ambient air pressure (P) in the surrounding environment. For the specific case illustrated, the leader is selected based on the ambient air pressure (P) in the surrounding environment. ambThe pressure is measured, a small amount (generally 5-50 mmHg) is added to account for the pulmonary artery pressure applied by the human body, and this pressure is converted to frequency based on a pressure-to-frequency calibration lookup table or formula in its memory. Such table or formula may be specific to individual sensors or may be generalized to all sensors of that type. Because a patient's pulmonary artery pressure usually adds a slight offset to the atmospheric pressure at the current weather station, this method is available for f xmt The best f from among them xmt This can provide a starting point for finding P amb The general concept of fitting a reader to a measurement using measurement parameters such as is described in detail in U.S. Patent No. 8,570,186, which is incorporated herein by reference in its entirety.

[0045] In step 2, the first selected f based on ambient pressure xmt A signal is transmitted, and the signal strength (SS), which is the amplitude of the ringback signal from the implanted object (implant), is measured. The signal strength should be high, but it should not saturate the receiving amplifier circuit used to measure it, because if both signals saturate, it is impossible to compare the strengths of different signals. To bring the signal strength (SS) into the desired strength range, the patient may need to move the position of the handheld reader (or, in the case of a pillow-type reader, move the patient's body relative to the reader) in response to an audible or visual signal from the reader. For example, the reader may emit a series of audible sounds that change in volume, pitch, or pulse frequency as the reader approaches or moves away from the optimal SS position. A different sound may be emitted when an acceptable SS is achieved. This may take several seconds. As an alternative, a self-adjusting gain amplifier, which can be logarithmic or other types of amplifier circuits, may be used. In this example, the SS value is converted to a digital code of 0 to 4096. In this case, 3800 to 4000 is considered an acceptable SS for home mode, and 3200 to 4000 is considered an acceptable SS for clinic mode.

[0046] Assuming all other parameters, such as link distance, antenna tilt angle, frequency-dependent circuit parameters, and the electrical characteristics of the intervening medium, are kept constant, the sensor's return signal is its f res ga f xmt When approaching a certain point, it always has a larger SS value.

[0047] SS is the first f xmt When within range, the patient is instructed not to move the reader relative to their body. The system proceeds to step 3, and with the reader held in place, all f xmt Excitation signals from the values ​​(four in the example in Figure 3) are used to read the SS. Generally, these SS measurements are performed quickly, within 5-20 milliseconds, and are completed before the patient moves their hand.

[0048] Step 4 is the first f xmt It determines whether it provides the best SS. If it provides the best SS, the remaining reading process is the first f xmt Continue using (Step 9).

[0049] Otherwise, the system proceeds to steps 5 and 6, and the best f xmt A "health check" is performed on the measurement when the excitation signal (band D in Figure 2) provides the highest signal intensity. xmt If it is in band D, the measured pulmonary artery pressure is P amb Since it is the sum of the smaller pressures applied by the body (generally 5-50 mmHg) and the ambient pressure P amb It is expected to be a relatively low value. The leader is P amb To provide direct measurements, the system can reasonably expect that band D will provide the best SS. amb It is possible to evaluate whether the pressure is sufficiently low. For example, if the leader's onboard pressure sensor shows a pressure exceeding 700 mmHg ambWhen this is measured, it corresponds to the expected measured pulmonary artery pressure of 705-750 mmHg. In this example, 705-750 mmHg corresponds to 13.429-13.557 MHz. Looking at Figure 2, this frequency range is f xmt It is clear that the strongest SS is obtained when the leader is selected from band B or band C instead of band D. amb >f in band D at 700mmHg xmt If the system determines that this yields the strongest SS, then the measurement is clearly erroneous, and the system is f of band D. xmt Ignore this and, before proceeding to step 7, select the band with the next highest SS from f xmt Select this option. It should be noted that in this example, this concept is applied in a different direction (P amb It may not be desirable to apply this to patients with symptoms like pulmonary hypertension (where Band A has the highest SS) when the pulmonary artery pressure is very low, because some patients have pulmonary artery pressures that are very high, up to 300 mmHg. In such cases, Band A is P amb Even with a low rating, it's possible to have the best SS (Sustaining Performance).

[0050] In the exemplary steps described above, the expected frequency value corresponds to a fixed assumption that the body adds 5–50 mmHg to the ambient pressure. In an alternative embodiment, different assumptions can be made based on values ​​learned from the patient's past pulmonary artery pressure measurements using a weighted learning algorithm or other type of learning algorithm. The concept of using past data to inform assumptions about future measurements can be applied to any type of measurement and is not limited to pulmonary artery pressure. In a specific exemplary embodiment, the reader may record the baseline pulmonary artery pressure (pressure above ambient pressure) of a given patient daily. Then, in step 1, for example, the rolling window average for the past 5 days is used. amb It can then be added to this mean and P amb The sum of the values ​​is converted to frequency, and the current f resAn estimate of is obtained. Next, the leader selects the f closest to that estimate for the first excitation pulse. xmt Select this option.

[0051] After the "health check" in Step 6, proceed to Step 7. Here, the leader considers the case where at least one of the four SS values ​​measured in Step 3 saturates the receiving circuit. If saturation occurs, in Step 8, the f that caused the saturation is checked. xmt You can select one of the values ​​and return to step 2. The audible cue from the reader will guide the patient again, and this time a new f xmt Then the optimal leader position is found, and the process is repeated. In step 3, multiple f xmt If the excitation pulse causes saturation, step 7 is P amb Select the frequency closest to the corresponding frequency and repeat the cycle. Finally, step 7 or step 9 provides the excitation f that gives the ringback signal with the highest SS. xmt To decide.

[0052] Now, from the path leading to either step 9 or step 10, f xmt If selected, the system can continue reading. In step 11, the reader selects f xmt Then, an excitation pulse is issued for a portion of the entire reading interval, 5 seconds in this example, and the sensor's f is measured using the method described in the reference prior art. resThe reader identifies the frequency. In a typical embodiment, the reader stimulates the sensor 1,000 times per second with an excitation pulse, directly sampling the sensor's frequency each time. In one embodiment, this is done by using a phase-locked loop (PLL) to lock an internal reader signal to the received sensor response signal. The reader opens the PLL and maintains the frequency of its output signal constant for a preset time interval selected to be slightly shorter than the expected duration of the rapidly decaying sensor response signal. With the PLL held constant at a frequency matching the now-vanished sensor signal, the reader has time to identify that frequency using a zero-cross timer or other method known in the art. This embodiment and other embodiments are described in detail in the referenced prior art.

[0053] In one embodiment, the excitation signal transmission frequency may be determined by an algorithm selected from a group including: selecting a transmission frequency closest to the estimated sensor resonance frequency based on measurement parameters; selecting a transmission frequency based on past measurements of the sensor resonance frequency; selecting a transmission frequency closest to the center of the full-scale range; selecting a transmission frequency most frequently used in past measurements; selecting a transmission frequency based on data from the patient's medical history; and selecting a transmission frequency based on the patient's posture measured by the reader's tilt sensor. For example, the patient's medical record may indicate that the patient generally has a particular PAP value higher than the surrounding environment. The reader uses this information to determine a suitable starting frequency for that patient. xmt This may determine the optimal position. It is well known in the art that when a patient is in a supine position, the patient's PAP generally increases by a certain amount, typically about 5-15 mmHg, compared to when the patient is in an upright position (sitting or standing). The reader determines the patient's posture and uses this information as input to determine the optimal position. xmt This may include an accelerometer or other tilt sensor for prediction. For example, starting f xmtThis can be derived by adding the patient's normal body-derived PAP to ambient pressure, and further adding the offset due to the patient's posture, which was measured for the patient at the time of the clinical calibration visit, where the patient measures the PAP delta (difference) between supine and standing positions using a reader.

[0054] In one embodiment, the sensor resonance frequency is proportional to cardiac pressure, and the sample processing may be further selected from detecting heart rate, respiratory rate, systolic peak, diastolic minimum, cardiac output, flow rate, arrhythmia, irregular breathing, vascular compliance, patient posture, patient activity level, patient health status, and comparison of any of these parameters with a predetermined threshold. In one example, patient activity level may be measured by an onboard accelerometer that calculates walking speed or step count. In one example, health status may include vital signs, comorbidities, medications, age, weight, etc.

[0055] In one embodiment, the frequency-determining circuit determines the frequency independently of the transmission frequency of the biasing pulse. In one embodiment, the reader does not need to "know" the transmission frequency of the biasing signal in order to determine the resonant frequency of the sensor.

[0056] Returning to Figure 3, step 12 is simply a check to confirm that the entire time interval for reading has elapsed. In our pulmonary artery pressure example, this interval is 20 seconds, allowing several respiratory cycles to occur. During this interval, the reader provides the patient with voice cues to hold the device firmly in place against the chest. During this interval, each f res The sample is accompanied by its own SS measurement, and individual SS measurements below the selected threshold may be rejected. res The most accurate f can be filtered using a moving window weighted average or other filtering means. res In order to obtain the measured values, many other low-pass filtering and spurious signal removal techniques may also be used.

[0057] If no interval has elapsed, the system can proceed to step 13. This step measures the average f during the previous 5 - second interval res to check whether it has moved from one transmission band to another. The reader obtains the maximum and minimum values of f during that interval and selects the midpoint. If the midpoint is approaching another f res , the reader changes to that new value in step 14, returns to step 2, and may then inform the patient to re - position the reader to keep SS within range. Although not shown, the reader may limit the number of times it changes f xmt in this way within a given measurement interval to avoid excessive reading times and re - positioning by the user. Also, to extract the entire pressure waveform during the measurement interval into a single value, a method other than the midpoint of the minimum and maximum values of f xmt may be employed. Examples include using the average value, arithmetic mean, mode, or weighted mean.

[0058] In step 13, if the filtered measurement f res is not approaching a different f xmt from the one currently in use, the system proceeds to step 15 and repeats the "sanity check" from step 5. If the system selects an f xmt corresponding to a pressure value much lower than the ambient pressure and fails the sanity check, then in step 16, it ignores all f xmt above that frequency and returns to step 2. In Figure 3, step 15 shows that f xmt is compared to P amb , but in an alternative embodiment, it may be compared to the midpoint of the measurement f res calculated in step 13. If f xmt is still a valid value and passes the sanity test in step 15, the process returns to step 11 for another 5 - second measurement interval of exemplary values.

[0059] ​​After the measurement interval, the system determines in step 12 whether the complete measurement time (20 seconds in Figure 3) has elapsed. If it has not, the control proceeds to step 13. If it has elapsed, the excitation pulse stops and the f rate continues. res No sample is taken. In step 17, the reader's processor calculates the mean pulmonary artery pressure (mPAP) for the total 20 seconds of measurements. Although not shown in the flowchart, the processor rejects any f values ​​throughout the process due to insufficient SS, measurements outside the expected range, or any other reason. res The number of samples may also be counted. If the cumulative number of rejected samples within a time interval exceeds a pre-set threshold, such as 10% of the samples, the reader may reject the entire read and return to step 1 to try again. Alternatively, a message indicating that the read failed may be issued to the user, advising them to wait until a new read is initiated or to contact customer support.

[0060] In step 18, the leader P amb The reader calculates a baseline mPAP that is greater than the given value. The reader stores this value and uses it along with other past values ​​to determine the appropriate f at the start of the next reading. res In some cases, this may be predicted. To perform this prediction, machine learning and artificial intelligence algorithms known in the art may be used.

[0061] Figure 3 includes parameters specific to pulmonary artery pressure (PAP) measurement, but can be easily generalized to any wireless sensor measurement based on a passive LS resonant tank energized by an external reader. To achieve this generalization, the specific parameters in Figure 3 are simply converted to general parameters as follows. ·P amb This can be any measurement parameter. • Steps 5 and 15, the "health checks," can be performed on any combination of parameter values ​​that are unlikely to occur physically in a given application. For example, in an application where the system reduces pressure to below ambient pressure, f xmt and P amb Instead of eliminating cases where both are high, we eliminate cases where both are low. In step 17, other parameters besides the mean of the final parameter may be calculated. In steps 17 and 18, the detection parameter can be any parameter other than PAP. Steps 17 and 18 are optional depending on the application. • A specific quantity (4 f xmt The reading interval (e.g., 20 seconds, sub-interval of 5 seconds) can be replaced with any value.

[0062] Other embodiments of the system that perform the steps in Figure 3 may include the following variations. The system can skip some steps, execute them in a different order, repeat them, or add further steps. ·P amb This may be an arbitrary detection parameter, and some other known value may be available for estimating the starting value and checking its health, so that the system can help select its biasing frequency. ·f xmt The intervals do not need to be equally spaced as shown in Figure 2; the intervals may vary for different patients or measurements. • All time intervals in the example may be changed. f after a 5-second interval xmt The re-evaluation of the step may be omitted. In other words, step 11 in Figure 3 may cover the entire reading interval and proceed to step 17. Steps 12, 13, 14, 15, and 16 may be omitted.

[0063] One embodiment of the reader may continuously monitor the midpoint or average of the PAP and determine the trend over time. This trend may be used to predict the optimal time to transition to a new band, ideally before signal strength is lost. xmt A migration may be performed.

[0064] One embodiment of the reader may monitor pulse pressure (PAPmax-PAPmin) for each heartbeat and predict when the next minimum or maximum value will occur. If the pulse pressure is high enough to cross over between adjacent bands, the algorithm uses the rate of change of pressure over time (dP / dt) to cross from one band to the next and back to the original band. xmt Predict the optimal point to change the band. The reader changes the band twice during each heartbeat to the band closest to the implant's and the patient's systolic (PAPmax) and diastolic (PAPmin) frequencies. xmt In some embodiments, the reader optimizes the frequency between the two bands. xmt In some cases, the two fs are rapidly dithered and the output is averaged to obtain a quasi-static PAP measurement. Dithering involves two fs xmt This can be done by switching between values ​​(one value per sample). Alternatively, it may be done by switching between two values ​​within the excitation burst of each signal sample.

[0065] Referring to Figure 4, one embodiment of a wireless sensor system that may be used in this disclosure is shown. A wireless system 10 is provided schematicly. The wireless system 10 may include a wireless reader 12 and a wireless sensor 14. The wireless sensor 14 may be a passive device, such as a device including a capacitor 16 and an inductor 18, or an active device. The wireless sensor 14 may be implantable, such as one that can be implanted in a living organism. For example, the wireless sensor 14 may be implanted in the human body to monitor a state or parameter within the human body.

[0066] The reader 12 may be configured to transmit an excitation pulse 20 to excite the sensor 14. The excitation pulse 20 may cause the sensor 14 to resonate and emit a ringing signal 22 at its resonant frequency. The resonant frequency of the sensor 14 may change based on the parameters detected by the sensor 14. The reader 12 may measure the frequency of the ringing signal 22 and determine the detected parameters. For example, the reader 12 may use a formula, a lookup table, or a calibration table to determine the detected parameters.

[0067] The reader 12 may include a receiver for receiving the ring signal 22 from the sensor 14. The receiver may include an antenna 24 or any other signal receiving device. The receiver may further include one or more filters, such as analog or digital filters, for filtering the signal 22 received from the sensor 14. The filters may be tuned to a passband to allow the reader 12 to receive a desired frequency band. In one embodiment, the reader may include a sensor 25.

[0068] As should be understood, the systems and methods described herein may be applied to any parameter to be measured or detected, such as pressure, temperature, or any other parameter.

[0069] Embodiments of this disclosure have been described above, and naturally, others will be able to conceive of modifications and variations by reading and understanding this specification. The following claims are intended to include any modifications and variations, insofar as they fall within the scope of the claims or their equivalents.

Claims

1. A wireless sensor reader configured to determine the resonant frequency of a sensor, A transmitting circuit configured to transmit a wireless biasing pulse to the sensor at a transmission frequency, thereby exciting a resonant circuit within the sensor and causing it to resonate at a frequency proportional to the measurement parameter, A receiving circuit configured to receive a response signal, which is a continuous wave at the resonant frequency of the sensor, from the sensor, The circuit includes a circuit for determining the frequency of the response signal of the sensor, The reader selects the transmission frequency of the biasing pulse from a plurality of distinct narrowband frequencies, and this selection is made before determining the frequency of the sensor's response signal. The reader acquires multiple samples of the sensor's response signal over a measurement time interval. The frequency of each of the plurality of samples of the response signal of the sensor is determined by a circuit for determining the frequency. A wireless sensor reader in which each of the plurality of samples of the response signal of the sensor is started by a biasing pulse of the same transmission frequency throughout the entire measurement time interval.

2. The wireless sensor reader according to claim 1, wherein the circuit for determining the frequency of the response signal of the sensor includes a phase-locked loop configured to lock an internal continuous wave signal to the response signal before the response signal is attenuated, such that the frequency of the internal signal matches the frequency of the response signal of the sensor.

3. The wireless sensor reader according to claim 2, wherein the phase-locked loop is further configured to hold the internal signal at a constant frequency before the response signal decays, and the constant frequency of the internal signal is equal to the frequency of the sensor's response signal.

4. The wireless sensor reader according to claim 3, further comprising a circuit for determining the frequency of the held internal signal while it is held at a constant frequency.

5. The wireless sensor reader according to claim 4, wherein the circuit for determining the frequency of the held internal signal is configured to measure the elapsed time of one period of the internal signal.

6. The wireless sensor reader according to claim 1, wherein the selection of the transmission frequency of the biasing pulse is performed before the determination of the frequency of the sensor's response signal.

7. The wireless sensor reader according to claim 1, further configured to use previously measured data to select the first transmission frequency of the biasing pulse at the start of the measurement time interval.

8. The wireless sensor reader according to claim 7, wherein the previously measured data is selected from ambient pressure, historical measurements of the average of reference pulmonary artery pressure, or calculation results using these parameters.

9. The wireless sensor reader according to claim 1, wherein the reader is further configured to measure the signal intensity of the response signal of the sensor.

10. The wireless sensor reader according to claim 9, wherein the reader is further configured to determine whether the measured signal strength is within a preset threshold window, the window having a lower limit for determining the minimum signal strength required for frequency detection by the reader and an upper limit for determining the maximum signal strength that enables the receiving circuit to be prevented from saturating.

11. The wireless sensor reader according to claim 10, further configured to provide the user with an audible cue, a visual cue, or a tactile cue indicating whether the response signal intensity of the sensor is within the window.

12. The wireless sensor reader according to claim 11, wherein the reader is further configured to select the transmission frequency by transmitting a plurality of excitation pulses, each having a different frequency selected from the plurality of distinct narrowband frequencies, the selection of the transmission frequency is based on the signal intensity of the sensor's response signal to each of the excitation pulses.

13. The wireless sensor reader according to claim 12, wherein the reader is further configured to repeat a portion of the process of selecting its transmission frequency when two or more of the plurality of distinct narrowband frequencies produce a sensor response signal that saturates the receiving circuit, the repeated portion of which includes repeating the step of the user repositioning the reader in response to the tactile cue.

14. The wireless sensor reader according to claim 7, further configured to use previously measured data to exclude the selection of a transmission frequency from a plurality of separate narrowband frequencies if the transmission frequency is not the frequency closest to the resonant frequency of the sensor.

15. The wireless sensor reader according to claim 7, wherein the reader records data during each reading interval such that future reading intervals include the previously measured data.

16. The wireless sensor reader according to claim 1, wherein the reader is further configured to analyze the sample of the sensor's response signal over a portion of the measurement time interval to determine whether the frequency of the sample has approached another frequency of the plurality of distinct narrowband frequencies than the current excitation signal frequency, and the reader is further configured to change the current excitation signal frequency to another frequency of the plurality of distinct narrowband frequencies for the remainder of the measurement time interval.

17. The wireless sensor reader according to claim 1, wherein the plurality of distinct narrowband frequencies are spaced along the frequency spectrum over the full-scale range of the sensor's resonant frequency.

18. The wireless sensor reader according to claim 17, wherein the transfer functions of the sensor with respect to adjacent separate narrowband frequencies on the frequency spectrum partially overlap with each other, and the response signal of the sensor at each frequency in the full-scale range of the sensor's resonant frequency has at least one reader transmit frequency that can excite the sensor to supply the reader with a sensor response signal of sufficient energy to identify the frequency of the response signal.

19. The wireless sensor reader according to claim 18, wherein the reader is further configured to select an excitation signal transmission frequency from among two adjacent frequencies if the intensity of the response signal is equal with respect to two adjacent frequencies.

20. The wireless sensor reader according to claim 19, wherein the selection of the excitation signal transmission frequency is performed by an algorithm selected from the group, namely, selecting a transmission frequency closest to the expected sensor resonance frequency based on measurement parameters; selecting a transmission frequency based on past measurements of the sensor resonance frequency; selecting a transmission frequency closest to the center of the full-scale range; selecting a transmission frequency most frequently used in past measurements; selecting a transmission frequency based on data from the patient's medical history; and selecting a transmission frequency based on the patient's posture as measured by the tilt sensor of the reader.

21. The wireless sensor reader according to claim 1, wherein the plurality of samples of the sensor's response signal over a measurement time signal include output waveforms of measurement parameters.

22. The wireless sensor reader according to claim 1, wherein the plurality of samples of the response signal of the sensor are processed to obtain output parameters, the processing of the samples is selected from averaging, low-pass filtering, band-pass filtering, weighted averaging, moving window averaging, Fourier transform, wavelet transform, differentiation, integration, curve fitting, calculation of area under the curve, trend analysis, correlation with other datasets, standard deviation, analysis of variance, minimum and maximum value detection, rise and fall times, or other mathematical data processing.

23. The wireless sensor reader according to claim 22, wherein the resonance frequency of the sensor is proportional to cardiac pressure, and the processing of the sample is further selected from the detection of heart rate, detection of respiratory rate, detection of systolic peak, detection of diastolic minimum, estimation of cardiac output, estimation of flow rate, detection of arrhythmia, detection of irregular breathing, estimation of vascular compliance, patient posture, patient activity level, patient health status, and comparison with any of the above parameters against a predetermined threshold.

24. The wireless sensor reader according to claim 22, wherein the patient's health status includes one or more of vital signs, comorbidities, medications, age, and weight.

25. The wireless sensor reader according to claim 1, further configured to calculate the rate of change of the resonant frequency of the sensor during the measurement time interval, and to automatically switch the excitation transmission frequency to the new value if the rate of change indicates that the resonant frequency of the sensor is likely to remain closer to the new value during the remainder of the time interval.

26. The wireless sensor reader according to claim 25, wherein the resonance frequency of the sensor is proportional to the cardiac pressure, and the automatic switching of the excitation frequency is performed each time the cardiac pressure approaches the maximum systolic or minimum diastolic value.

27. The wireless sensor reader according to claim 1, wherein the circuit for determining the frequency determines it independently of the transmission frequency of the biasing pulse.

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