Multi-sensor RF detection

Abstract

RF motion sensors can be configured to operate in a common vicinity to reduce interference. In some variations, interference can be reduced through timing and / or frequency synchronization. In some variations, a master RF motion sensor can transmit a first radio frequency (RF) signal. A slave RF motion sensor can determine a second RF signal that minimizes interference with the first RF frequency. In some variations, interference can be reduced through additional transmission adjustments (e.g., pulse width reduction or frequency and / or timing jitter differences). In some variations, an apparatus can be configured with multiple sensors in a configuration that transmits the RF signal in different directions to mitigate interference between transmit pulses from the RF motion sensors.

Description

[0001] Divisional application statement

[0002] This application is a divisional application of a PCT international application with an international application date of April 20, 2016 and international application number PCT / EP2016 / 058791, which entered the Chinese national phase on September 30, 2017, and a Chinese invention patent application with the invention name “Multi-sensor Radio Frequency Detection” and application number 201680021222.9.

[0003] CROSS-REFERENCE TO RELATED APPLICATIONS

[0004] This application claims the benefit of the filing dates of U.S. Provisional Patent Application No. 62 / 149,916, filed April 20, 2015, and U.S. Provisional Patent Application No. 62 / 207,670, filed August 20, 2015, the disclosures of which are hereby incorporated by reference. Technical Field

[0005] The present invention relates to circuits and sensors for detecting characteristics of moving and living objects. More particularly, the present invention relates to such sensors for generating radio frequency emissions (e.g., range-gated pulses), motion sensing, and particularly to improving sensor operation when in close proximity to similar sensors. Background Art

[0006] Continuous wave (CW) Doppler radar motion sensors transmit a continuous wave radio frequency (RF) carrier and mix the transmitted RF with the returning echo to produce a difference frequency equivalent to the Doppler shift caused by a moving target. These sensors do not have well-defined range limitations (i.e., they can receive signals for both near and far objects, where the received signal is a function of the radar cross section). This can lead to false triggering, i.e., motion artifact interference. They can also have undesirably high sensitivity at close ranges, leading to false triggering.

[0007] A pulsed Doppler motion sensor is described in U.S. Patent No. 4,197,537 to Follen et al. A short pulse is transmitted, and its echo self-mixes with the transmitted pulse. The pulse width defines the range-gated region. When the transmit pulse ends, the mixed end and target returns arriving after the transmit pulse end are not mixed and are therefore gated.

[0008] McEwan's U.S. Patent No. 5,966,090, "Differential Pulse Radar Motion Sensor," discloses a differential pulse Doppler motion sensor that transmits two pulse widths alternately. The Doppler response from each width is then subtracted to produce a range-gated Doppler sensing area with a fairly constant response to distance.

[0009] Pulse radars (such as those described in McEwan's U.S. Patent No. 5,361,070, "Ultra-Wideband Radar Motion Sensor") produce a very narrow sensing area related to the width of the transmitted pulse. Dual-pulse Doppler radar motion sensors (such as those described in McEwan's U.S. Patent No. 5,682,164, "Pulse Homodyne Field Disturbance Sensor") transmit a first pulse and, after a delay, generate a second pulse that mixes with the echo from the first pulse. This creates a range-gated sensing zone with defined minimum and maximum ranges. A disadvantage of UWB radar motion sensors is that they are not recognized as intentional radiators by RF regulatory agencies worldwide. They also have difficulty sensing objects at medium distances and, in some embodiments, can be susceptible to RF interference.

[0010] A modulated pulse Doppler sensor is described in McEwan's U.S. Patent No. 6,426,716. The range-gated microwave motion sensor includes adjustable minimum and maximum detection ranges. The device comprises an RF oscillator associated with pulse generation and delay elements to generate transmit and mixer pulses; a single transmit (TX) / receive (RX) antenna or a pair of separate TX and RX antennas; and an RF receiver including a detector / mixer with associated filtering, amplification, and demodulation elements to generate a range-gated Doppler signal from the mixer and echo pulses.

[0011] In U.S. Patent No. 7,952,515, McEwan discloses a unique holographic radar. It adds range gating to a holographic radar to restrict the response to a specific area in the emission direction. McEwan states that this allows for sharper, less cluttered radar holograms of the imaging surface, particularly when imaging internal image planes or slices through materials. Range gating enables stacked hologram technology, in which multiple imaging surfaces can be stacked along the emission direction.

[0012] In U.S. Patent Application Publication No. 2010 / 0214158, McEwan disclosed an RF amplitude sampler for holographic radar. McEwan described that the RF amplitude sampler can well resolve the interference pattern generated by narrow-band holographic pulse radar.

[0013] In U.S. Patent Application Publication No. 2014 / 0024917, McMahon et al. describe a sensor for physiological sensing that can be configured to generate an oscillating signal for transmitting radio frequency pulses for range-gated sensing. The sensor can include an RF transmitter configured to transmit the pulses and a receiver configured to receive reflected RF signals from the transmitted RF pulses. The received pulses can be processed to detect physiological characteristics such as motion, sleep, breathing, and / or heartbeat.

[0014] Improvements may be needed in sensors and / or their signal processing for radio frequency sensing, such as in the case of physiological characteristic detection where multiple sensors are in a common location. Proximity of sensors may result in undesirable interference, which may, for example, reduce the signal-to-noise ratio. Summary of the Invention

[0015] One aspect of some embodiments of the present technology relates to a sensor for detecting a physiological characteristic using a radio frequency signal.

[0016] Another aspect of some embodiments of the present technology relates to such a sensor having circuitry configured to generate a pulsed radio frequency (RF) signal that is transmitted toward an object (e.g., a person). A receiver detects the signal reflected from the object, which is amplified and mixed with a portion of the initial signal. The output of the mixer can then be filtered. The resulting signal can contain information about, for example, the person's motion, breathing, and cardiac activity, and can be referred to as a raw motion sensor signal. The phase difference between the transmitted signal and the reflected signal can be measured at the receiver or by a separate processor to assess any of the person's general body motion, breathing, and cardiac activity.

[0017] In some variations, the RF motion sensor may be configured to reduce interference from other RF motion sensors.

[0018] In some variations, the sensors may be configured to be synchronized across a group of local sensors to avoid temporal overlap of RF pulses.

[0019] In some variations, the sensors may be configured to be synchronized across a group of local sensors to avoid overlapping RF pulses in frequency.

[0020] In some variations, the pulse signal from each sensor may be adapted to reduce the probability of interference by the various means described herein (eg, by pulse width reduction, timing jittering, and / or frequency jittering).

[0021] In some variations, multiple (e.g., two) sensors may be configured (e.g., having a common housing structure) to face different or appropriate directions to avoid interference (e.g., positioned midway along the bed at the headboard or foot of the bed).

[0022] In some variations, multiple sensors may allow for optimal placement to mitigate noise. These variations may depend on sensor antenna polarization or antenna beam pattern to provide the necessary RF interference attenuation.

[0023] Some variations of the present technology may include an RF motion sensor configured to operate in a multi-sensor configuration. The RF motion sensor may include an RF transmitter. The transmitter may be configured to transmit a sensing signal, such as a pulsed RF signal. The RF motion sensor may include a receiver configured to receive a reflected RF signal of the transmitted RF signal to detect motion of a reflective surface. The transmitter may be configured to transmit the pulsed RF signal in synchronization with another RF motion sensor in proximity to the RF motion sensor to mitigate interference between transmitted pulses from the RF motion sensor.

[0024] In some variations, the transmitter may be synchronized in time to interleave the transmitted pulsed RF signal with a pulsed RF signal transmitted by another RF motion sensor. Synchronization between RF motion sensors may involve the transmission of a clock signal. Synchronization between RF motion sensors may involve the transmission of a jittered synchronization signal. Optionally, the RF motion sensor detects or can detect the timing from the transmitted pulsed RF signal. In some variations, the RF motion sensor may detect the synchronization signal independently of the transmitted pulsed RF signal. The RF motion sensor may include an infrared signal transmitter adapted for the timing of the transmitted pulsed RF signal. The RF motion sensor may include an interface for a wired connection to another RF motion sensor. The wired connection may be configured for the timing of the transmitted pulsed RF signal. The transmitter may be synchronized in frequency with the transmitter of another sensor to reduce interference.

[0025] Optionally, the transmitter may include a variable oscillator configured to adjust frequency in response to detected interference noise. The transmitter may be further configured for frequency dithering. The transmitter may be further configured for time dithering. The transmitter may be configured to dither the frequency of the pulsed RF signal.

[0026] Some variations of the present technology may include a radio frequency motion sensor. The radio frequency motion sensor may include: an radio frequency transmitter configured to transmit a radio frequency sensing signal, such as a pulsed radio frequency signal; and a receiver configured to receive a reflected radio frequency signal of the transmitted radio frequency signal to detect motion of a reflective surface. The transmitter may be configured with a dithering timing that differs from the dithering timing of another radio frequency motion sensor in the vicinity of the radio frequency motion sensor to mitigate interference between transmitted pulses from the radio frequency motion sensor. The dithering timing of the transmitter may be pseudo-random. The transmitter may be configured with frequency dithering.

[0027] Some variations of the present technology may include a radio frequency motion sensing device. The device may include two or more radio frequency sensors. Each sensor may include an radio frequency transmitter configured to transmit a sensing signal, such as a pulsed radio frequency signal, and a receiver configured to receive a reflected radio frequency signal of the transmitted radio frequency signal to detect motion. The device may include a housing to maintain the sensors in a configuration that transmits radio frequency signals in different directions to mitigate interference between transmitted pulses from the radio frequency motion sensors. The sensors may be positioned to direct the transmitted pulses at a relative angle of approximately 90 degrees to 270 degrees. The sensors may be positioned to direct the transmitted pulses at a relative angle of approximately 180 degrees or greater.

[0028] Some variations of the present technology may include a system for transmitting radio frequency, for example, for sensing. The system may include a master radio frequency motion sensor and a slave radio frequency motion sensor. The master radio frequency motion sensor may be configured to transmit a first radio frequency (RF) signal. The slave radio frequency motion sensor may be configured to transmit a second RF signal. The system may be arranged or configured to minimize interference between the RF signals of the two sensors.

[0029] In some variations, the slave RF motion sensor may be configured to transmit a second RF signal that minimally interferes with the first RF frequency signal. The master RF motion sensor and the slave RF motion sensor may be adapted to be housed within a single or common housing. The master RF motion sensor and the slave RF motion sensor may be positioned at an angle of approximately 90 degrees within the single or common housing. The RF transmitter may be configured to transmit at least one synchronized RF pulse signal. The slave RF motion sensor may be further configured to receive the synchronized RF pulse signal. The slave RF sensor may be further configured to detect the received synchronized RF pulse signal at an intermediate frequency. The master RF sensor may be further configured to transmit at least one RF pulse signal in a separate industrial, scientific, and / or medical (ISM) transmission band. The master RF sensor may further include an infrared (IR) transmitter, such as an IR transmitter configured to transmit an IR synchronization signal. The slave RF sensor may include an infrared (IR) receiver, such as an IR receiver configured to receive the transmitted IR synchronization signal.

[0030] Optionally, the master RF sensor and the slave RF sensor may further include a master-slave oscillator circuit. The master-slave oscillator circuit may further include a multi-wire cable interconnect, such as a multi-wire cable interconnect configured to transmit timing and jitter synchronization information from the master RF sensor to the slave RF sensor. At least one of the master RF motion sensor and the slave RF motion sensor may include at least one resonant oscillator circuit. The at least one resonant oscillator circuit may include a quartz crystal.

[0031] In some variations, the slave RF motion sensor may include at least one resonant oscillator circuit and a voltage-controlled RF oscillator. The voltage-controlled RF oscillator may be configured to synchronize its RF signal frequency with that of the master RF motion sensor. The voltage-controlled RF oscillator may be configured to synchronize the RF frequency with that of the master RF sensor by detecting a high voltage that causes a high level of interference noise, detecting a low voltage that causes a high level of interference noise, and moving the voltage-controlled RF oscillator to a central control voltage position between the high and low voltages. Optionally, at least one of the first RF signal and the second RF signal may have an RF pulse width of approximately 0.5 μs.

[0032] The master RF sensor may be configured to provide a first jitter time to the first RF signal. The slave RF sensor may be configured to provide a different jitter time to the second RF signal. The master RF sensor may include a first binary ripple counter and an XOR gate. Similarly, the slave RF sensor may include a second binary ripple counter and an XOR gate. The first and second binary ripple counters and the XOR gate may be configured to generate a pseudo-random jitter time. The master RF sensor may include a first dielectric resonant oscillator modulated by a first voltage. The slave RF sensor may include a second dielectric resonant oscillator modulated by a second voltage. Optionally, the first and second RF signals may be at different frequencies.

[0033] Some variations of the present technology may include a system for delivering radio frequency, for example, for sensing. The system may include a first radio frequency motion sensor and a second radio frequency motion sensor. The first radio frequency motion sensor may be configured to transmit a first radio frequency (RF) signal. The second radio frequency motion sensor may be configured to transmit a second RF signal. The system may be adapted to minimize interference between the RF signals of the two sensors.

[0034] In some variations, the first frequency motion sensor may be configured to receive an indication of a frequency transmitted from the second RF motion sensor, and the second RF motion sensor may be configured to receive an indication of a frequency transmitted from the first RF motion sensor. The first frequency motion sensor may be configured to adjust the frequency of the first RF signal in response to the received indication of the frequency transmitted from the second RF motion sensor. Each of the first frequency motion sensor and the second frequency motion sensor may be configured to access a lookup table comprising selectable frequencies at which the sensors are operable. The first frequency motion sensor may be configured to select a frequency from the first lookup table, and the second frequency motion sensor may be configured to select a frequency from the second lookup table. The first lookup table may include odd-numbered frequencies, and the second lookup table may include even-numbered frequencies. The first frequency motion sensor and the second RF motion sensor may be configured to adjust their respective frequencies using the Network Time Protocol (NTP).

[0035] The first frequency motion sensor and the second RF motion sensor can be configured to adjust their respective transmission frequencies in response to detecting interference. The first frequency motion sensor and the second RF motion sensor can be configured to adjust their respective transmission frequencies based on a predetermined temperature coefficient. The first frequency motion sensor and the second RF motion sensor can be configured to check or adjust the frequency of their transmitted RF signals in response to a geographic location input. At least one of the first frequency motion sensor and the second RF motion sensor can be configured to operate in a low-power mode when no motion is detected. The first frequency motion sensor and the second RF motion sensor can be configured to transmit a continuous clock signal via a wired or wireless link.

[0036] In some variations, at least one of the first frequency motion sensor and the second RF motion sensor can be configured to: transmit periodic center frequency values ​​read from each corresponding sensor over a network; and / or adjust the frequency used by each sensor to transmit to minimize interference between the first and second sensors. At least one of the first frequency motion sensor and the second RF motion sensor can be configured to: dynamically detect its respective current center frequency; and / or periodically adjust said frequency to match a recognized lookup table center frequency, such that interference between the two sensors is minimized while remaining within defined spectrum limits. Optionally, the first frequency motion sensor and the second RF motion sensor can be configured such that: a frequency range can be dynamically scanned to detect minimum and maximum interference; and / or the center frequency of at least one sensor can be adjusted to the frequency associated with the minimum value. The sensors can communicate via the frequency of maximum interference. At least one of the first frequency motion sensor and the second RF motion sensor can be configured to: detect temperature changes; and / or initiate polling between the sensors based on the detected temperature changes to adjust the center frequency of at least one sensor.

[0037] In some variations, the system can be arranged to minimize interference between the RF signals of the two sensors by frequency jittering one or more oscillators of the sensors that generate the RF signals. For example, the voltage level of at least one of the one or more oscillators can be ramped to generate the frequency jitter. The system can be arranged to minimize interference between the RF signals of the two sensors by timing jittering the pulses of the RF signals of the two sensors. For example, the voltage level of a diode coupled to at least one of the one or more oscillators can be ramped to achieve timing jittering of at least one sensor. In some cases, at least one of the one or more oscillators can be a dielectric resonant oscillator.

[0038] Other aspects, features, and advantages of the technology will become apparent from the following detailed description taken in conjunction with the accompanying drawings, which are a part of this disclosure and illustrate, by way of example, the principles of the technology. Further aspects of the technology will become apparent from the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Further exemplary embodiments of the technology will now be described with reference to the accompanying drawings, in which:

[0040] Figure 1 is a diagram of an exemplary detection system of a radio frequency physiological sensor suitable for implementing the technology;

[0041] Figure 2 is a conceptual diagram illustrating the operation of some embodiments of the present technology;

[0042] Figure 3 is a diagram illustrating a conceptual structure and process flow for obtaining sensor signals suitable for some embodiments of the technology;

[0043] Figure 4 shows exemplary components involved in generating a range-gated radio frequency signal using switched oscillation in some embodiments of a sensor circuit of the present technology;

[0044] Figure 5A and Figure 5B is a diagram illustrating generation and detection of RF pulses suitable for some embodiments of the technology;

[0045] Figure 6 is a diagram of a composite receiver RF signal suitable for some embodiments of the technology;

[0046] Figure 7 is a diagram of a transmitted signal (700), a received signal (702), and a resultant receiver RF signal (704); which includes baseband noise, as described in the present technology. The constant variations seen in the resultant receiver RF signal (704) may cause baseband interference;

[0047] Figure 8A and Figure 8B is a diagram illustrating an example of a signal path traveled by an RF signal found in some embodiments of the present technology;

[0048] Figure 9 is a graphical representation of sensor locations suitable for some embodiments of the present technology;

[0049] Figure 10A It is a signal representation of the synchronous timing of pulse generation.

[0050] Figure 10B It is a signal representation of the "jitter" produced by the pulse;

[0051] Figure 11A It is a signal representation of the asynchronous timing of pulse generation and reading;

[0052] Figure 11B is a signal representation of an overlapping signal described in the present technology;

[0053] Figure 12 is a diagram of IR signal timing connections suitable for some embodiments of the present technology;

[0054] Figure 13 is a three-wire synchronous master-slave test circuit used in some embodiments of the technology; and

[0055] Figure 14 is an example of a housing suitable for some embodiments of the technology.

[0056] Figure 15 The sample ratio between the sensor baseband range, the intermediate frequency and the filter range is shown.

[0057] Figure 16A is a signal diagram of exemplary in-phase and quadrature baseband signals in the time domain without interference.

[0058] Figure 16B This is a signal diagram of an intermittent interference signal.

[0059] Figure 16C Figure 1 is a graph of a signal with peak noise greater than 200 mVrms, where the timing of the peak noise level is unpredictable.

[0060] Figure 17 A sample schematic showing how RF modulation and demodulation timing is established with a 4MHz ceramic resonant oscillator and associated binary ripple counter. DETAILED DESCRIPTION

[0061] 1. Overview

[0062] like Figure 1As shown, some embodiments of the present technology may implement sensing or detection devices 100 and 102 for detecting physiological characteristics of multiple users or patients. The sensors may be stand-alone sensors or may be coupled to other devices, such as respiratory therapy devices, to provide automatic treatment responses based on analysis of physiological characteristics detected by the sensors of the device. For example, a respiratory therapy device having a controller and a flow generator may be configured with such a sensor or communicate with such a sensor and may be configured to adjust the pressure treatment generated at a patient interface (e.g., a mask) in response to the physiological characteristics detected by the sensor. Alternatively, when the flow generator is not being used by the patient, such a sensor may be used to detect the patient's physiological characteristics to inform them of the advantages of using the flow generator. An exemplary respiratory therapy device is described in International Patent Application No. PCT / US2015 / 043204 filed on July 31, 2015, the entire disclosure of which is incorporated herein by reference.

[0063] A typical sensor of such a device may employ a transmitter to transmit radio frequency (RF) waves, such as RF pulses for range-gated sensing. A receiver, which may optionally be included in combination with the transmitter, may be configured to receive and process waves reflected from the patient's body. Signal processing may be employed, such as by a processor of the device that activates the sensor, to obtain physiological characteristics based on the received reflected signals. An example of the operation of such a sensor may be found in U.S. Patent Application Publication No. 2009 / 0203972, the entire disclosure of which is incorporated herein by reference.

[0064] Figure 3 A schematic diagram of a sensor or a component of a sensor is shown in FIG. Figure 3 As shown, a transmitter transmits a radio frequency signal toward a subject, such as a person. Typically, the source of the RF signal is a local oscillator (LO). The reflected signal is then received by an RF receiver, amplified, and mixed with a portion of the original signal. The mixer's output may then be filtered. The resulting signal may contain information about, for example, the person's motion, breathing, and cardiac activity and is referred to as a raw motion sensor signal. The phase difference between the transmitted and reflected signals can be measured to assess any of the person's motion, breathing, and cardiac activity.

[0065] The raw motion sensor signals may be processed to obtain signal components reflecting body motion, respiration, and cardiac activity. Body motion may be identified by using a zero-crossing or energy envelope detection algorithm (or more complex algorithms) and used to form a "motion start" or "motion stop" indicator. For example, such motion detection algorithms may be based on the aforementioned U.S. Patent Application Publication No. 2009 / 0203972, International Patent Application No. PCT / US14 / 045814, U.S. Provisional Patent Application No. 62 / 149,839 filed on April 20, 2015, and U.S. Provisional Patent Application No. 62 / 149,839 filed on August 20, 2015. 62 / 207,687 The method disclosed in the patent application No. 1050006, the entire disclosure of which is incorporated herein by reference. Respiratory activity is generally in the range of 0.1 to 0.8 Hz and can be obtained by filtering the initial signal using a bandpass filter having a passband in the region. Cardiac activity is reflected in the higher frequency signal and can be obtained by filtering using a bandpass filter with a passband in the range of 0.8 to 10 Hz (e.g., 70 heart beats per minute is about 1.17 Hz in the range).

[0066] Such respiration and motion sensors can be range-gated RF motion detectors. The sensor can be configured to accept a DC power supply or battery input and provide, for example, four analog motion channel outputs having in-phase and quadrature components of the respiration and motion signals of a person within the detection range. In the case of a pulsed RF motion sensor, range gating can help limit motion detection to only a preferred area or range. Thus, detection by the sensor is possible within a limited distance from the sensor.

[0067] like Figure 4 As shown, a typical sensor 402 of the present technology can employ one or more oscillators, such as oscillator 404, such as a dielectric resonant oscillator (DRO). The DRO can be a high-Q DRO, which is a narrowband oscillator (e.g., a DRO operating at 10.525 GHz), such as an oscillator containing a box of dielectric material. DROs typically produce stable RF frequency characteristics and are relatively unaffected by changes in temperature, humidity, and component parasitics. In some cases, the sensor can be a sensor described in U.S. Patent Application Publication No. 2014 / 0024917, the entire disclosure of which is incorporated herein by reference.

[0068] like Figure 5AAs shown, a pulsed RF signal has two main modulation parameters. These parameters are the pulse repetition interval (PRI) (where duration is denoted by T) and the pulse width (PW) (where duration is denoted by τ). The term pulse repetition frequency (PRF) is the inverse of the PRI. For example, a sensor may transmit a 10.525 GHz RF signal that is pulse modulated at a frequency of approximately 250 kHz to produce an RF pulse signal with a pulse repetition interval of 4 μs, specified by T, and a pulse width timing of 2 μs, specified by τ. Thus, the RF signal in this example would be 0.5 μs long and generated every 4 μs (i.e., a 12.5% ​​duty cycle).

[0069] The sensor can be a homodyne transceiver capable of transmitting and receiving RF signals. Thus, the transceiver can measure the magnitude and phase of the received signal relative to the transmitted signal. The phase and / or magnitude of the received signal changes relative to the transmitted signal or the distance traveled by the received signal as the target moves. As a result, the demodulated magnitude detection receiver output signal is a measure of the target's movement and / or the distance traveled by the signal. While such a magnitude detector can be optionally implemented, in some cases, other circuit elements or detectors can be implemented to replace or provide the functionality of the magnitude detector. For example, any detector circuit configured to detect signal modulation can be used, such as a peak detector, an envelope detector, or a harmonic mixer circuit.

[0070] Both the transmitted RF signal and the received RF signal may be provided to the input of a homodyne receiver switching magnitude detector (eg, RF magnitude detector). Figure 5B As shown, the received signal can be detected during the receive time interval period when the sensor is transmitting an RF pulse. In this regard, the magnitude detector can detect the RF pulse each time the RF pulse is transmitted. In some embodiments, the magnitude detector can detect the signal during a 5 ns period during the first 12 ns of the RF pulse transmission (i.e., the 5 ns can be anywhere within the first 12 ns, e.g., starting at 7 ns, 1 ns, etc.).

[0071] When there is only a single RF pulse source, the transmitted and received RF signals can be expressed mathematically as follows:

[0072] Transmitted RF signal: A Sin(ω1t+θ1); and

[0073] Received RF signal: B Sin(ω1t+θ2)

[0074] where A and B are the amplitudes, ω1 is the angular frequency, t is time, and θ1 and θ2 are the corresponding phases. (The time of travel is implicit in the phase difference between θ1 [e.g., the reference phase at the oscillator] and θ2 [after bouncing off the object].)

[0075] Because both signals originate from the same source, they also have the same frequency. Therefore, when they are superimposed, the resulting RF signal has an amplitude that varies with the phase and amplitude of the reflected signal. The transmitted and received RF signals can be combined using the following formula: a and b are amplitudes, x is time multiplied by angular frequency (2πft), and β and α are phases.

[0076] like Figure 6 As shown, the resulting signal 602 may be the result of modulating the transmitted RF signal with the received RF signal. The resulting signal 602 may have a periodic sinusoidal amplitude envelope 600 and a phase that varies only with the distance and movement of the target. Thus, the superimposed signal changes with the distance to the target or the movement of the target.

[0077] Time Jitter

[0078] When operating two or more sensors, oscillator timing differences and / or dithering can facilitate noise interference reduction. For example, in some sensors, the timing of pulse generation can be dithered relative to the timing associated with the base pulse repetition frequency by including a dithering circuit (not shown) (e.g., coupled to or included with pulse generator 408). FIG10b shows a signal representation of "dithering" pulse generation (where the start time of the pulse is varied relative to the overall pulse generation timing). Through such dithering, the overall pulse repetition frequency can be varied such that the pulse start time is linearly delayed or advanced relative to the nominal overall pulse center (i.e., the second pulse train is at a slower pulse repetition frequency than the first pulse train). If the PRF remains fixed, this has the net effect of changing the position of the pulse start time relative to its nominal start time. This can be achieved using a synchronized ramp dithering circuit. An exemplary synchronized ramp dithering circuit can be implemented using a voltage-controlled delay element based on a basic RC (resistance-capacitor) time constant. The ramped control voltage causes a varying varactor diode capacitance, which in turn causes a varying resonator frequency. In this manner, the frequency of the pulse generation circuit oscillator and the associated PRF are varied by approximately 1% approximately every 1 ms in a synchronous and linear manner. In some examples, the linear ramp function may be at 1 kHz, which produces associated jitter in the PRI and PW timing. Jitter can be used to remove synchronous RF demodulation noise artifacts. Ramp jittering may be used because it is easier to implement, but may produce tone artifacts if not synchronized with the RF modulation and demodulation timing. Synchronous ramp jittering prevents the generation of unwanted tones. However, the use of a timing jitter circuit complicates unit-to-unit PRI timing variations, thereby complicating pulse timing synchronization.

[0079] In some sensors, the RF modulation and demodulation timing is established by a 4 MHz ceramic resonant oscillator and an associated binary ripple counter (see Figure 17 To achieve low demodulation noise, the oscillator timing can be subsequently "synchronized dithered" with a linear ramp function (e.g., 1 kHz) that produces an associated jitter on the PRI and PW timings. The use of a timing dither circuit complicates the unit-to-unit PRI timing variations. These timing variations are further exacerbated by the use of ceramic resonators, which have lower frequency tolerance and higher drift than quartz crystals. In summary, while synchronized dithering can mitigate RF jammer noise, the second approach to RF jammer noise reduction, namely pulse timing synchronization, creates problems due to jitter and / or timing variations. For example, Figure 10A As shown, the read signal of the first sensor may overlap with the pulse of the second sensor, and vice versa.

[0080] In order for two sensors to coexist without generating RF interference, the first sensor should transmit its RF pulses during the second sensor's silent period, and vice versa. Figure 11A As shown, the read signal of the first sensor (white line in the figure / indicated as "RL" in the figure) occurs only during the period when the second sensor is not transmitting an RF signal. Similarly, the second sensor only reads the signal when the first sensor is not transmitting. However, in practice, the asynchronous nature of sensor operation (jitter, frequency difference and frequency drift) causes the RF pulses of the first sensor to periodically overlap with the receive timing of the second sensor, as shown in FIG. Figure 11B In this regard, due to the nature of the sensors, a read signal from a first sensor may occur during the time that a second sensor is transmitting an RF pulse, and vice versa.

[0081] 2. Noise Source

[0082] Sensors, such as the sensors of the illustrated detection devices 100 and 102, positioned in close proximity to each other, may suffer from radio frequency (RF) coexistence issues. Figure 2 As shown, two sensors 300 and 302 can be positioned so that their respective RF pulses are projected in the direction of opposing sensors. In this regard, sensor 300 can transmit RF pulse 312 in the direction of sensor 302, and sensor 302 can transmit RF pulse 310 in the direction of sensor 300. As a result, sensor 300 can receive reflections of its RF pulse 312, a direct RF pulse 310 from sensor 302, and a double-reflected RF pulse from the sensor (not shown). Thus, the RF pulse received by the sensor may include not only desirable reflections of the RF pulse generated by the sensor's originally transmitted RF signal, thereby causing baseband interference when the received RF pulse is demodulated. (Generally, in some cases, a baseband signal may be a signal having a very narrow frequency range, i.e., a non-zero and negligible spectral magnitude only at frequencies near the origin (referred to as f=0)).

[0083] although Figure 2 While only the sensor's RF pulses are shown, RF waves from other devices can also be received by the sensor. Such RF waves can originate from devices both near and far from the sensor. Due to the nature of RF waves, they can penetrate obstacles such as walls and other obstructions, as well as geographical terrain. Therefore, embodiments of the present technology can significantly reduce a sensor's susceptibility to RF coexistence issues.

[0084] When the received RF signal comes from a device or source other than the transmitting sensor, noise can be introduced into the received RF signal. The transmitted, received, and combined RF signals can be represented by the following mathematical formula:

[0085] The RF signal transmitted by the first source:

[0086] A Sin(ω1t+θ1); and

[0087] RF signal received at the second source:

[0088] A Sin(ω2t+θ2)

[0089] The resulting combined RF signal:

[0090]

[0091] Where A and B are amplitudes, ω1t and ω2t are the corresponding time-dependent angular frequencies, and θ1 and θ2 are the corresponding phases. Combining the transmitted signal from the first source and the received RF signal from the second source can result in an RF signal with a periodic sinusoidal amplitude envelope and a phase that varies continuously with time and is independent of any movement of the target. Figure 7 In the example of FIG, the transmitted signal 700 from the first source can be combined with the received signal 702 from the second source to produce a resultant signal 704. As can be seen, the resultant signal 704 has a periodic sinusoidal amplitude envelope and a phase that varies continuously over time regardless of any movement of the target. (Since the phase varies continuously over time, this is not necessarily the case in the example of FIG. Figure 7 [Left hand side] (represented as circles). This continuous variation in the resulting signal can be introduced when the received signal 702 is combined with the transmitted signal 700 at an intermediate frequency that is a multiple of the transmitted frequency. This variation can cause baseband interference.

[0092] The amount of interference generated by RF signals transmitted from devices or sources other than the receiving sensor may depend on the received signal strength of the unwanted interfering RF signal. In this regard, the strength of the unwanted interfering RF signal may depend on the path the interfering RF signal travels before reaching the receiving sensor. For example, Figure 8AAs shown, the interference signal 806 can be reflected by the object 804 and received by the receiving sensor 800. Therefore, the power of the interference RF signal 806 is reduced when it reaches the receiving sensor 800 compared to the case where the signal reaches the receiving sensor 800 directly. The power formula of the interference signal after reflection is given by the following formula:

[0093]

[0094] in:

[0095] P r = the power of the reflected interfering signal;

[0096] P t = transmitter power;

[0097] G t = Gain of the transmitting antenna;

[0098] A r = the effective aperture (area) of the receiving antenna (most of the time denoted as Gr);

[0099] δ = radar cross section or scattering coefficient of the target;

[0100] R r = the distance from the transmitter to the target (for the reflected signal) and

[0101] F = Pattern propagation factor (usually close to 1)

[0102] On the contrary, Figure 8B As shown, the interference signal 808 can be generated by the second active source 802 and received directly by the sensor 800 without any reflection. Because no reflection of the interference signal 808 occurs, the power of the interference signal 808 decreases only based on the distance traveled. Therefore, the power of the interfering RF signal decreases based on the distance. The power of the interference signal 808 that reaches the receiver directly without being reflected is given by the following formula:

[0103]

[0104] in:

[0105] P d = the power of the interfering signal that is not reflected;

[0106] P t = transmitter power;

[0107] G t = Gain of the transmitting antenna;

[0108] A r = the effective aperture (area) of the receiving antenna (most of the time denoted as Gr);

[0109] δ = radar cross section or scattering coefficient of the target;

[0110] R d = the distance from the transmitter to the receiver (for direct transmission and reception); and

[0111] F = Pattern propagation factor (usually close to 1)

[0112] Therefore, when two sensors are placed in a room, the interference signal level from the second unit can be higher than the signal transmitted by and reflected back to the first sensor because of the shorter effective path length and the absence of attenuation due to scattering.

[0113] When an interfering RF signal is received at a sensor, the interfering RF signal will cause baseband noise under certain conditions: (1) the interfering RF frequency is in-band (i.e., near 10.525 GHz, 10.587 GHz, 9.3 GHz, 61 GHz, 24 GHz, 10.45 GHz), (2) the interfering RF signal is received during the sensor's receive time interval, (3) the frequency of the RF signal transmitted by the sensor and the frequency of the interfering RF signal have a difference frequency, which is a multiple of the pulse repetition frequency of the transmitted frequency signal, and (4) the RF interfering signal has sufficient amplitude to generate an interfering noise signal.

[0114] These four conditions can be restated as follows, where RF1 represents the RF center frequency of the primary sensor, RF2 represents the interference source RF center frequency, IF1 represents the intermediate frequency of RF1 (generally, in some contexts, such as in communications and electronic engineering, an intermediate frequency (IF) can be considered as a frequency offset from a carrier frequency as an intermediate step in transmission or reception), and IF2 represents the intermediate frequency of RF2:

[0115] (1) Interference may occur when RF2 is within the demodulation frequency range of RF1, typically + / - 25 MHz.

[0116] (2) Interference may occur when the pulse repetition frequency (PRF2) of RF2 is a multiple of the frequency of RF1. More specifically, let RF1 = RF2 + / - n(PRF2), where n is any integer;

[0117] (3) Because the receiver is a synchronous phase detector, interference may occur when the information about the demodulated RF2 includes the frequency of IF1 or any of its odd harmonics. In other words, RF2 (i.e., a signal modulated by AM / FM modulation or any other modulation scheme) contains information about IF1 or its odd harmonics;

[0118] (4) Interference may occur when RF1 and RF2 are combined and then demodulated, where RF2 has a sufficient signal level to produce a baseband noise component.

[0119] To reduce this baseband noise interference, the present technology contemplates the implementation of several solutions. First, the sensors can be synchronized in time to avoid any overlap of the RF pulses in time. Second, the sensors can be synchronized to avoid overlap of the RF pulses in frequency (i.e., RF1 = RF2 + / - (n + 0.5) (PRF2)). Third, the sensors can be configured to pulse in a manner that makes the likelihood of interference negligible. Fourth, two or more sensors can be placed in a housing facing different directions (e.g., placed along the middle of the bed at the headboard or foot). Examples of each implementation are described in detail herein.

[0120] In the case of a distance-gated RF sensor using a DRO as a reference oscillator, the second or subsequent sensor may have a stable transmit frequency and behavior, making it an almost optimal source of interference to similar sensors in the vicinity (i.e., when considering a system of multiple contactless distance-gated sensors).

[0121] To mitigate this interference with efficient low-noise operation with more than one sensor in close proximity, the following implementation can be done:

[0122] (i) Timing synchronization can be implemented between sensors via wired or wireless communication (using precise timing signals between cooperating sensors), or

[0123] (ii) Each sensor can be configured to function independently (no cooperation required) in a manner that does not cause said almost perfect interference.

[0124] For the latter case (i.e., without inter-sensor cooperation), time and / or frequency dithering can be used. Timing dithering can be used to propagate noise, while frequency dithering can be used to prevent interference. For example, as discussed in more detail herein, in some embodiments, a voltage ramp across a diode coupled to a timing oscillator can change the diode capacitance. This results in a change in the oscillation frequency of the timing oscillator, thereby causing timing jitter, such as the timing pulses contained in the pulsed RF signal generated by the dithering. Additionally, by increasing the supply voltage of a DRO (dielectric resonator oscillator), the frequency is changed, resulting in frequency jittering of the RF signal (e.g., by ramping the voltage from 2.5V to 3.0V and then to 2.5V).

[0125] 3. Timing synchronization

[0126] Time synchronization of RF pulses can be implemented by generating synchronization pulses from the first sensor (master) to the second sensor (slave). In this way, the second sensor will transmit its RF pulses during the silent period of the first sensor. The solution can have Figure 9 The noise level is the same as shown in the "Baseline Noise" setting. Instead of going through a master sensor, synchronization of all sensors can be driven by independent controllers in a manner very similar to how a master sensor drives one or more slave sensors. Or, in fact, the sensors can act as peers, for example, distributing control and communication among devices in the field, whereby each device communicates directly with surrounding devices without having to communicate through / via a master device.

[0127] To implement timing synchronization between sensors, the following factors may be considered. First, the timing of the sensors may include synchronization jitter, for example, at intervals of 1 ms or more or less, and therefore synchronization may not be easy to achieve. Second, the timing of the sensors may be controlled by ceramic resonators with a frequency accuracy of only about 1%. Third, the slave units should be enabled to detect loss of synchronization and maintain the timing of the sensors. Fourth, both clock and jitter synchronization signals may be transmitted from the master sensor to the slave sensors, for example to help address the use of jitter and the asynchronous nature of operation. Fifth, synchronization should be achieved with sub-microsecond timing accuracy to maintain the required RF pulse interleaving lock. Sixth, the master and slave sensors should be aware that they need to transmit or receive synchronization signals. (i.e., the sensors should automatically synchronize when needed or be set to synchronize when installed)

[0128] RF pulse signal

[0129] Due to these considerations, particularly given the jittery and asynchronous nature of timing, some variants may include the generation of timing synchronization, which includes the transmission of clock and jitter synchronization signals and can have sub-microsecond timing accuracy. There are many ways to achieve this, including detecting RF pulse signals from the master unit. In this regard, when the pulse signal from the master unit is received by the slave unit, the timing of the slave unit is adjusted to ensure that the slave unit does not transmit the RF signal at a timing associated with the master unit's pulse signal. However, because the RF pulse signal may not be at the clock frequency of the oscillator, the timing architecture may need to be changed. In addition, a phase-locked loop (PLL) may need to be implemented, but this may be complicated by jitter. If timing jitter is not used, the synchronization requirements above are reduced to those of PRF pulse timing synchronization, which is a lower requirement. Pulse timing jitter may not be used, and instead, in some cases, RF frequency jitter may be used to achieve enhanced interference noise reduction.

[0130] 3.2. RF pulse signal detection in the intermediate stage

[0131] Another approach for transmitting a clock and jitter synchronization signal with sub-microsecond timing accuracy is to detect the master sensor's RF pulse signal at the IF (intermediate frequency) stage via a slave sensor. This solution is not easy to implement due to the complexity of the circuitry required to receive, amplify, and condition the received signal, in addition to phase-locking it to a local 4 MHz oscillator, but it is feasible, especially if digital sampling is employed.

[0132] 3.3. Single RF signal

[0133] In another approach, a separate RF synchronization signal can be sent. For example, a separate Industrial, Scientific, and Medical (ISM) band RF signal can be generated to provide a synchronization signal from the master unit to the slave units. In this regard, the ISM RF signal can potentially be piggybacked on an existing RF communication channel via wireless means.

[0134] 3.4. Other wireless signals

[0135] In an alternative approach, timing synchronization may be implemented via other wireless communication methods, including RF signals such as Bluetooth, Wi-Fi, ZigBee, or other proprietary wireless means.

[0136] 3.5. Infrared signal

[0137] In an alternative approach, the timing synchronization can be implemented by photonic means, for example by light pulses and in particular by infrared signals. Figure 12 As shown, the master sensor 1201 can send an infrared signal 1204 to the slave sensor 1202. In this regard, the master sensor 1201 can include an infrared transmitter / receiver, and the slave sensor 1202 can include an infrared transmitter / receiver. Thus, the master sensor 1201 can transmit a timing signal from the infrared transmitter to the infrared receiver of the slave sensor 1202. However, achieving the required coverage and timing accuracy at the required speed may be complicated. For example, depending on the distance between the sensors, the infrared signal may be delayed, thereby failing to provide proper synchronization. In addition, interference issues may be encountered, such as high-speed IR signals from other devices (e.g., TV remote controls) "interfering" with the output. Other methods may also be used, such as fiber optic connections or transmission via visible light communication (e.g., pulsed LEDs or fluorescent lights) in the range of 400 to 800 THz (780 to 375 nm).

[0138] 3.6. Cable coupling

[0139] Another method of timing synchronization can be implemented through a wired connection. For example, a multi-wire cable (e.g., a three-wire cable or a two-wire cable, etc.) can be used to connect the master sensor to the slave sensor. This three-wire cable synchronizes the master-slave oscillator circuit as shown in FIG. Figure 13 A three-wire cable can connect a master sensor to a slave sensor, allowing the master sensor to transmit timing and jitter synchronization information from the master sensor to the slave sensor. Figure 13 On the left side of the diagram is the master sensor circuit 1301, while on the right side of the diagram is the slave sensor circuit 1302. The master sensor circuit may include a reset U1 pin 11 (not shown) connected to ground via a 1k resistor to enable reset control. Additionally, the master sensor circuit 1301 may include a 4MHz oscillator input U1 CLK pin 10 buffered by a gate driver / buffer (and provided as a clock output to the slave device). Furthermore, the master sensor circuit may include a 1kHz dithered output U1 Q12 pin 1 buffered by a gate driver / buffer and provided as a reset output to the slave device. Finally, the master circuit may be connected to ground (0V) and provided as an output to the slave sensor.

[0140] The slave sensor circuit may include a reset U1 pin 11 connected to ground via a 1k resistor to enable reset control, and a 1kHz dithered output received from the master circuit and provided to the slave circuit reset U1 pin 11 via a 2.2Nf series capacitor. The slave sensor circuit may further include a 4MHz oscillator output gate driver / buffer received from the master circuit to drive the collector of transistor Q1 via a 1kHz resistor. Finally, the slave circuit may include circuit ground (0V) provided as an input from the master circuit.

[0141] More generally, the master clock output is transmitted through a first buffer (on the master circuit) onto a wire that is received by a second buffer on the slave circuit. The output from the second buffer is provided to the slave clock input. Similarly, the reset output is transmitted through a buffer onto a wire that is received by a buffer on the slave circuit. The output from the second buffer is provided to the reset pin via a differentiator / high-pass filter. Only the leading edge of the reset pulse passes through to the reset pin. The slave circuit can be connected to ground.

[0142] The master sensor and the slave sensor can be synchronized by a three-wire cable by sending a pulse width of, for example, about 0.5 us from the master sensor. Such a pulse width achieves out-of-phase synchronization of the RF pulses.

[0143] As already mentioned, if timing jitter is not used, the aforementioned synchronization requirements are reduced to those of the PRF pulse timing, which is a lower requirement. In this case, the three-wire sequential circuit described is reduced to a two-wire sequential circuit. This two-wire circuit can be implemented by issuing a master reset output and running the clock. This eliminates the master clock requirement.

[0144] Wired connections can achieve synchronization requirements and can optionally provide other functions as well. For example, the cable can be implemented to power a second (or subsequent) unit. Therefore, wires can allow sensors to be placed farther apart without necessarily introducing more wires and cables. In addition, the two wires can provide timing synchronization and power to the second unit via modulated signals. Wires can also reduce the need for other wireless chipsets; for example, a group of sensors can form a pair, only one of which has a Wi-Fi or Bluetooth interface and space for a power adapter or battery, while the second is simply connected via a cable without the need for a separate Wi-Fi or other radio capability, because the relevant control / sensor data is also modulated onto the wires. More complex wired connections based on Ethernet can also be used.

[0145] Both the three-wire and two-wire synchronization circuits described above can be implemented on the sensor's circuitry, or can be located in the connecting wires. The advantage of the latter is that the synchronization circuitry and associated costs will not be included in each unit.

[0146] 3.7. Quartz crystal

[0147] In addition to the timing synchronization solutions described above, or as a standalone solution, the oscillator can be implemented using a quartz crystal. Therefore, because quartz crystals have high frequency tolerance and low frequency drift, a lower-frequency synchronization signal will be required. Furthermore, only a single synchronization signal is required (e.g., a clock), as quartz crystals can be implemented without jitter.

[0148] 4. Frequency synchronization

[0149] Another approach to reducing RF interference between multiple sensors is to synchronize the sensors' RF frequencies. In this way, the sensors can coexist without generating RF interference. For example, if two sensors transmit at RF frequencies f1 and f2, respectively, at time t, the received signals due to f1 and f2 are:

[0150]

[0151] Maximum interference occurs between f1 and f2 when f1–f2 = n*PRF±IF, where IF is the intermediate frequency and n is an integer. Minimum interference occurs when f1–f2 = (n+0.5)*PRF±IF.

[0152] 4.1. Make the frequency different

[0153] To minimize interference, different sensors can be configured to different frequencies. In this regard, sensors can be dynamically set to different frequencies. For example, a sensor can implement a DRO where the frequency is a function of voltage. For example, a 1V DC change can result in a 1.5MHz RF frequency change.

[0154] The voltage-controlled RF oscillator of the first sensor can synchronize the RF frequency to that of the second unit. In this regard, the control circuitry within the first sensor can detect the DRO voltage that results in a high level of interference noise and adjust the DRO voltage to a minimum noise voltage by moving it to a central control voltage position (i.e., a low noise region) between these two "high noise level" voltages (e.g., where there are multiple interference maxima when constructive, destructive, constructive, destructive, etc. modes exist). It has been demonstrated that RF frequency synchronization between the two sensors results in the same noise level as if only a single sensor were used.

[0155] 4.2. Automatic detection of interference and communication between sensors via wired or wireless networks or via coded interference pulses

[0156] Another approach to minimizing interference is to have each of multiple sensors detect its corresponding center frequency. Each sensor can then transmit its corresponding frequency value to the other sensors via a wired or wireless connection. The sensors can then adjust their corresponding center frequencies to achieve optimal spacing to minimize interference between them. In this way, more than one sensor can collaborate to reduce or avoid interference. Such a configuration can avoid the need to transmit clock signals, clock edges, and / or resets. Furthermore, the described approach can tolerate delays and other potential issues that may arise in the communication channel, allowing sensors to operate over links with poor quality of service (QoS). However, this approach is not limited to networks with poor QoS and can be implemented over links with good or high quality QoS. Furthermore, transmitting the corresponding center frequencies can potentially avoid the use of buffer circuits (unless required), dedicated cables, and / or synchronous radio or infrared links. In contrast, continuously transmitting clock signals, clock edges, and / or resets between sensors may require defined QoS, including latency, bandwidth, and other parameters. A network such as the Internet or an ad-hoc peer-to-peer Wi-Fi link such as Wi-Fi Direct using Wi-Fi Protected Setup (WPS) are examples of such links (eg, these are examples of links suitable for center frequency transmission or clock signal transmission).

[0157] Detection of the center frequency may require circuitry involving several additional circuit components (e.g., extracting a signal from a mixer) and may be enabled by a digital sensor. In this regard, a first digital sensor may send a notification of its latest or most recent center frequency reading to a second digital sensor, and the second digital sensor may send its latest or most recent center frequency reading to the first sensor. For example, the first digital sensor may transmit a center frequency of 10.252791 GHz and the second digital sensor may transmit a center frequency of 10.525836 GHz. The first and second digital sensors may then adjust their respective center frequencies to achieve an optimal spacing of, for example, 125 kHz, to minimize interference between them. The optimal amount of adjustment may be based on the IF and PRF configurations of the respective sensors. While digital sensors are described, transmission of frequency values ​​may also be enabled by an analog baseband sensor configured to share information with a processor in an attached device.

[0158] The transmission of the center frequency may be performed over Wi-Fi, Ethernet, Bluetooth, or any other type of connection. The transmission may involve an authentication handshake followed by periodic transmission of the center frequency value. Optionally, the transmission of an updated value may occur when the value deviates from a past value by a defined threshold. In some embodiments, the transmitted data may be encoded in packets over the Wi-Fi link.

[0159] 4.3. Frequency Lookup Table

[0160] Another technique for establishing frequency synchronization is to use a frequency lookup table in each sensor. In this regard, the sensors can each store a copy of the lookup table (or a function or formula used to dynamically calculate these frequencies). For example, one or more tables can include a set of odd frequencies and a set of even frequencies. The odd and even frequencies can be selected to be mutually interferingly zeroed. The sensor can then be programmed to select frequencies from the odd and even tables for operation. Thus, these tables can span an area within the allowed spectral limits of the filter associated with the sensor, where the area is within the controllable center frequency range of the sensor. For example, frequencies can be selected from:

[0161] (0.5+n)*PRF;

[0162] Where n is an integer and PRF is the pulse rate frequency. This configuration can allow for a reduction in sensor memory if the sensor can be programmed to calculate the frequency using the required mathematical formula.

[0163] In some embodiments, the first sensor can check whether it is operating at or near a frequency in the even table or the odd table and make fine adjustments to match one of these close (or closest) frequencies on either table. For example, the first sensor can adjust its frequency to the closest frequency in the even table. The second sensor can then adjust its frequency to the closest frequency in the odd table, thereby achieving minimal interference.

[0164] Communication between a defined pair (or multiple sensors) can occur only once, at installation. Thus, a defined pair configuration can help eliminate the need for ongoing wired or wireless transmissions between sensors. Thus, the complexity introduced by constantly updating frequencies during ongoing operation can be minimized or eliminated.

[0165] The one-time pairing process of a defined pair (or multiple sensors) can be performed by wired or wireless means. For example, near field communication (NFC) and / or accelerometers can be used to enable "touch to pair," thereby enabling communication of information between sensors using proximity and / or control signals.

[0166] Alternatively, the pairing process can be repeated periodically (e.g., via storage and forwarding network), such as occasionally or on a best-effort basis, to verify that the control parameters have not changed. In this regard, a change in the location or condition of one or more sensors can cause the system to prompt the user to perform a manual re-pairing, or the re-pairing process can be performed automatically in the background.

[0167] When two or more sensors are in close proximity, a portion of each table can be fenced for each corresponding sensor. For example, each sensor can be assigned to a range of possible frequencies on the even table, or to a range of possible frequencies on the odd table. Additionally, a switch or some other type of input can be present on the sensor to define the preferred behavior. For example, a switch can be provided to adjust which frequency a sensor will operate at, or to select whether a sensor will operate at frequencies from the even table, frequencies from the odd table, or a portion thereof.

[0168] It is also desirable that other metrics of the RF environment be collected by one or more sensor devices of the system. For example, other metrics of the RF environment that may be collected may include spacing or distance measurements between sensors, as well as the relative orientation of the sensors. Using these metrics, a configuration can be programmed so that the sensors cooperate to minimize mutual interference. If, before or after performing a pairing routine, a sensor is placed in a location where high levels of residual interference may occur, the sensor can provide notification to reposition or reorient one or more sensors.

[0169] 4.4. Detection of friend and foe

[0170] As mentioned above, there are situations where multiple sensors (e.g., two or more) are in close proximity and could strongly interfere with each other if no countermeasures are taken. However, while the sensors may interfere, they are "friends" in that they can be configured to have specific behaviors when detecting and adjusting to mutual interference. In contrast, third-party sources of RF signals may interfere with the operation of the sensor by accidentally or actively obstructing the pulse sequence. Such third-party sources operating at a similar center frequency as the sensor can be considered "enemies"; examples could be sensing technology from another manufacturer or supplier operating with a similar frequency / pulsing strategy, or perhaps a malicious user attempting to intentionally disrupt the operation of a medical cardiopulmonary sensor. Other exemplary sources of interference could include indoor / hospital (or outdoor) combined passive infrared sensors (PIRs) and microwave security detectors (e.g., where the microwave detector components operate at similar RF center frequencies), high-powered aviation radars, and / or military, police, traffic management, or vehicle radars, all of which may generate similar center frequencies that could interfere with the operation of the sensor.

[0171] In the case of interference caused by friendly sensors, the sensor can be programmed to intentionally scan a frequency range to determine the presence of interference. In this regard, one or more friendly sensors can perform a search pattern, each modifying its center frequency to attempt to maximize interference. Upon maximizing interference, the sensor can then reconfigure its center frequency to minimize interference. The sensor can then determine the frequency range between the maximum and minimum interfering frequencies. The sensor can then determine whether the frequency range corresponds to, for example, a known frequency range. If so, the sensor can assume that another sensor of a known type is the source of interference. This scanning preferably occurs when there is no motion near the sensor.

[0172] Based on the determination that a friendly sensor is an interference source, the sensor can initiate communication (e.g., using Manchester encoding). For example, one or more sensors can adjust their respective center frequencies around the determined interference maximum until two or more sensors meet the maximum. In this regard, a first sensor can shift its center frequency at a predetermined rate, with a second (or multiple other sensors) detecting when the interference maximum is reached. Each sensor can communicate a recognized maximum point and then agree on which sensor should shift to find the minimum frequency point. Upon reaching the minimum, the sensor adjusted to the minimum value will remain at the center frequency until correction is required, for example, to account for temperature drift or other variations.

[0173] This cooperative action between friendly sensors can be achieved through a base station and / or through a mesh network of devices. In this regard, the sensors are reconfigurable, for example, having the ability to dynamically adjust the center frequency by, for example, including a processor that controls, for example, a voltage-controlled oscillator, varying voltage, and / or other RF characteristics (including pulse timing and radiated power). In another embodiment, encoding can be applied to some RF bursts to enable faster communication between "friends" without using other communication channels.

[0174] Thus, communication of polling events using control signals to a local or remote processor is enabled to account for and block transient interfering signals. This allows for a system that does not require intercommunication (i.e., does not require precise knowledge of the current center frequency). Thus, a temperature change reference (e.g., detection of a temperature change) can be used to trigger or initiate polling between sensors to update the frequency of each sensor to avoid interference due to recent temperature changes.

[0175] Based on the maximum interference detected and the center frequency of the sensor itself, the frequency of the interfering signal can be measured. This is done by (a) knowing the center frequency of the sensor, (b) optionally scanning the center frequency, (c) locating the maximum interference, and (d) deducing the frequency of the interference source. In the case where a maximum (or high / elevated) interference is detected, it can be inferred that the interference source has a component at that frequency. Once the interference frequency is known, the sensor can be reconfigured, the user can be alerted, or even a third party interference source can be reconfigured (for example, in the case where the configuration of the third party sensor can be achieved (for example) by turning it off, adjusting the angle, distance, frequency, power level, etc.). The maximum interference is defined by the maximum noise; this can be measured by looking at the higher frequency components of the baseband or intermediate frequency. For the example of a sensor with a baseband range from DC to 200 Hz and an intermediate frequency of 8 kHz, the filter range to check for interference can be said to be 500 to 1500 Hz (roughly speaking, it is spaced in multiples of 10; one centered around 100, one around 1000, and one around 10,000) (see Figure 15 ). Figure 16A Exemplary in-phase and quadrature (IQ) baseband signals in the time domain without interference are shown. Figure 16B shows an intermittent interference signal, Figure 16C The signal is shown to have a peak noise greater than 200 mVrms and an unpredictable peak noise level.

[0176] 4.5. Adjust the center frequency to avoid enemies (or other interference sources)

[0177] As previously mentioned, strong interference sources that are not from other sensors (i.e., friends) can be considered enemies. An enemy can transmit an RF signal with a center frequency close to or the same as the frequency transmitted by one or more sensors. Therefore, it is desirable for sensors to be able to operate in the presence of enemies that may transmit blocking signals or other malicious RF emissions.

[0178] In some embodiments, continuous detection of RF interference caused by an enemy by a sensor in collaboration with another sensor or multiple sensors may prompt the system to adjust the frequency on which it is operating. For example, the system may search an agreed-upon lookup table of values ​​or other agreed-upon blocks of radio spectrum to find a situation where the anomalous external interference is minimized. If the third-party source is a sensor using a similar pulse scheme, a shift in the zero interference frequency may be seen (e.g., shifting the center frequency by 125kHz and / or by adjusting the PRF may be sufficient to minimize the interference). If this is unsuccessful, it can be seen that the sensor can gradually adjust the center frequency to build an image of the local RF environment and perform an optimization process (e.g., using gradient descent interference avoidance) to locate the interference minimum over time. In some instances, this may require a large change in the center frequency, for example, a move from 10.587GHz to 9.3GHz (or vice versa).

[0179] If the system is not successful in minimizing external interference caused by enemies and / or other sources, the system will notify the user. For example, the system may try to adjust the operation through the clock, the transmission of an adjusted center frequency, or the center traversal of a special lookup table. If this adjustment is unsuccessful, the system may notify the user that the readjustment was "unsuccessful" because the residual interference detected exceeds a predetermined acceptable threshold. Optionally, such information can be provided to the user only if the interference actually persists. In certain extreme interference situations, the sensor's RF radio may be automatically shut down and an error signal may be set (e.g., displayed on the screen). As a result, the sensor cannot process and / or extract physiological signals and, therefore, cannot detect the user's biometric parameters. In addition, if detected, the biometric parameters may be inaccurate.

[0180] 5. Noise reduction without synchronization requirements

[0181] In some embodiments, noise reduction can be achieved without synchronization between two or more sensors. In this regard, the sensors can be configured to minimize RF coexistence issues without synchronizing the frequency or timing of the sensors.

[0182] 5.1. Reduce RF pulse width

[0183] One such technique may include reducing the RF pulse width to reduce the probability of interference. Figure 5AThe pulse width, τ, can be used to determine the length of the RF pulse signal. Reducing the pulse width while maintaining the pulse repetition interval, PRI, does not adversely affect sensor operation. Furthermore, shorter pulse widths are less likely to be modulated by other pulses than longer pulses. The lowest pulse width value can be selected to meet regulatory approval standards for RF signal bandwidth and spurious signal levels.

[0184] 5.2. Dithering Each Sensor

[0185] Another technique for noise reduction can include dithering the pulse timing of each sensor differently or maintaining the pulse timing of each sensor at a constant frequency offset from each other. In this regard, the different timing of the master and slave sensors can reduce the chances of the sensor RF pulses locking in phase with each other.

[0186] 5.3. Increase jitter timing

[0187] It is also possible to increase the pulse timing jitter between the two sensors and make the pseudo-random less noisy. Similar to jittering the timing of each sensor, the jitter cycle can be extended and pseudo-random generated for one or both of the master and slave sensors. In some examples, a second binary ripple counter and an XOR gate or a microcontroller or processor can be used to generate the extended pseudo-random jitter cycle. As stated, the synchronous nature of the jitter or pseudo-random timing jitter with the PRF (and IF) is significant so that tone artifacts are not generated by the phase-sensitive demodulator receiver of the sensor. In one example, the diode can be connected to a timing oscillator (e.g., a timing oscillator) configured to control the transmission of the timing pulses from the DRO. Figure 4 The voltage level across the diode may ramp up, thereby changing the diode capacitance. This can cause the oscillation frequency of the timing oscillator to change, potentially leading to timing jitter.

[0188] 5.4. Dithering RF Frequency

[0189] Another technique for asynchronously reducing noise and interference is to dither the dielectric resonator oscillator (DRO) RF frequency to mitigate PRF frequency lock. Frequency dithering also has the advantage of mitigating external RF interference. In some instances, an additional circuit may be required to modulate the DRO's drain voltage or dither the DRO's supply voltage from a voltage-controlled regulator. In this regard, by ramping the DRO's supply voltage, the frequency of the DRO output can be adjusted.

[0190] Frequency dithering can allow multiple sensors to coexist in a common vicinity. For example, by employing frequency dithering, the center frequency of each sensor is shifted so that there is no statistically significant chance of interference between sensors in normal operation. In addition to being used for timing dithering, this technique can also be used on its own.

[0191] 5.5. Single shell

[0192] Another technique to reduce noise between sensors is to locate the sensors in a single housing unit. Figure 14 As shown, two sensors 1406 and 1408 are placed within housing unit 1400. Sensor 1406 is placed 180 degrees apart from sensor 1408 so that there is minimal, if any, interference between signals 1402 and 1404. Figure 9 The noise level between sensors is lowest when the sensors are at least 90 degrees apart. Therefore, when placing the sensors in the housing, they should be at least 90 degrees apart. The benefit of this technique is that the sensors can be easily synchronized through direct connection.

[0193] 5.6. Orientation

[0194] Because the signal level of interference sources is important, sensor location plays a role in noise reduction. Placing sensors close together and within line of sight generates the greatest interference noise. This noise can be mitigated by orienting the sensors to increase the effective path length. Separating sensors further apart and positioning them at angles is an effective way to reduce coexistence noise.

[0195] Polarization

[0196] When the RF signals transmitted and received by the sensors are circularly polarized (i.e., their RF signal electric and magnetic fields have preferred transmission and reception directions), further noise reduction can be achieved by arranging the sensors so that the polarization of one sensor is orthogonal to that of the other. In this way, the reflected mobile signal is preferred (unattenuated due to its polarization), while the received interfering RF signal is rejected (suffering attenuation due to its orthogonal polarization).

[0197] 6. Combined configuration

[0198] Noise reduction can also be achieved by using more than one of the previously described noise reduction architectures and / or techniques. In Table 1 below: "S" denotes synchronization, and "D" denotes dithering. For the terms in brackets "()", this means the "S" and / or "D" cases (i.e., the description of Table 1 is simplified). For Table 1, "t" denotes timing (which includes IF timing and PRF timing). "f" denotes RF center frequency. "None" denotes no intervention (i.e., the annotation / none is insignificant in the existing case). The case of 1 coexisting sensor is shown, but can be extended to (1, 2...n) linked sensors. It should be noted that timing synchronization means synchronization of the wired or wireless control signal (i.e., the first control signal); if dithering is also used (simultaneous synchronization of timing and dithering of timing), a second control signal is used to facilitate synchronization. For timing synchronization, this means that the PRF timing is locked. For dithering, this means that the IF and PRF are synchronized, but dithered (hence the requirement for the second control signal).

[0199] A potential limitation of independent timing synchronization is that it requires good RF pulse isolation. (RF bleeds through the RF signal during the off-periods of the RF modulation, resulting in poor RF pulse isolation.) Therefore, it is necessary to shut down the RF transmitter between pulses or use other methods to eliminate this bleed-through.

[0200] When considering Table 1, the combination of timing jitter and frequency synchronization [t(D)f(S)] may perform well. The combination of timing synchronization and frequency synchronization [t(S)f(S)] may also perform well, especially if there is good isolation, or timing synchronization and timing jitter and frequency synchronization [t(S,D)fS)].

[0201] Table 1:

[0202] t(of IF and PRF) f none none S(D) none S(D) D none S D S S(D) S D D D none none D

[0203] 7. Other considerations

[0204] 7.1. Correction for temperature changes

[0205] As certain operating parameters change, the center frequency of the sensor can drift, even under the control of a DRO. In this regard, changes in both ambient and internal temperature can cause the sensor's frequency output to drift. In some instances, if a high-power light or heat source is located near the RF sensor or in the same housing as the RF sensor, and such a source is turned on and off over time, the sensor may experience repeated and significant temperature changes. Center frequency drift may also occur when a product with a processor and sensor is first turned on and the housing reaches the system's expected operating temperature, which may be higher than the ambient temperature.

[0206] For the case of a system that includes separate temperature monitoring, the detection of temperature changes (with reference to the rate at which the temperature changes over time) can be used to adjust the sensor transmission frequency. Thus, embodiments may include design parameters that assist the sensor in outputting a specific frequency regardless of any temperature changes.

[0207] A system with two or more sensors that sends a continuous clock or associated reset synchronization signal over a wired or wireless link with defined QoS can automatically correct for any temperature changes or related changes in center frequency. In this regard, the sensors can be adjusted using the techniques previously described with respect to QoS.

[0208] A system with two or more sensors that transmits periodic center frequency readings from the sensors can maintain optimal spacing. For example, the sensors can transmit the readings over a network, allowing one or more sensors to be adjusted in a manner that achieves and maintains a defined frequency spacing. Consequently, interference between sensors can be minimized. This correction can be achieved based on a change or delta in the center frequency of a sensor exceeding a defined threshold.

[0209] For systems with two or more sensors using a lookup table, after the initial pairing process, each sensor can dynamically detect its current center frequency (e.g., due to drift due to changes in temperature or other parameters) and continuously or periodically adjust its frequency to match the agreed-upon lookup table center frequency. Such adjustments can thereby minimize interference between sensors while ensuring that the sensors remain within defined spectral limits.

[0210] RF sensor variations and processor-controlled offsets can also be used to estimate temperature, allowing the RF sensor alone to be used to estimate temperature with a certain degree of resolution. In this regard, temperature can allow for sensor activation effects, and furthermore, the resolution enables temperature sensing without the need for a separate temperature sensor. Therefore, prior knowledge of the oscillator's temperature coefficient is not required.

[0211] 7.2. Reducing sensor synchronization events

[0212] The number of times a sensor communicates its actual center frequency to nearby sensors can be reduced by reading and accurately setting the center frequency during manufacturing. In this regard, the maximum and minimum operating temperature limits of the DRO or quartz crystal are known. Based on these maximum and minimum limits, the temperature coefficient can also be determined, as the DRO's operation can be linear. Based on the operating frequency output by the sensor, adjustments can be made based on the known temperature coefficient to correct for inaccuracies caused by operating temperature.

[0213] 7.3. Third-party Timing Correction

[0214] In embodiments where the sensor measures its own center frequency, the accuracy of the clock generating the RF signal can be known and adjusted when determining the center frequency. For example, the Network Timing Protocol (NTP) can be used to determine the actual frequency of the clock at a given moment. Timing calibration can then be performed on the clock, so other sensors can be adjusted to ensure they operate with a previously defined frequency difference. NTP is a network protocol for synchronizing clocks between systems over packet-switched, variable-latency data networks (e.g., the Internet, using the User Datagram Protocol (UDP) on port 123).

[0215] Commercial crystals can have known clock rates and accuracy. For example, a crystal might have an accuracy of 20 parts per million, with variations associated with temperature. In cases where temperature changes are slow, such as over a 10 or 30 minute period, timing calibration can be performed on a 4 MHz clock. Once the current time is available, it can be sent to other devices.

[0216] To provide the current time to other sensors, the clock rate, in this example a 4 MHz clock, can be mixed with a frequency change rate of, for example, 10.525 GHz. As a result of the mixed signals, harmonics of the 4 MHz clock signal appear on the received signal. Therefore, based on the output, there is a frequency of:

[0217] n*actual frequency

[0218] Where n is an integer, and the actual frequency is the output frequency of the sensor (10.525 GHz in the current example). Due to accuracy issues, the clock rate may differ slightly from the advertised rate. Continuing with the above example, the clock rate may be 4.01387 MHz. To ensure accurate timing between sensors, the clock rate can be adjusted until the output frequency does not include frequency deviation and / or beat frequency. Based on the adjusted rate, it can be determined that the crystal is operating at n times the clock rate.

[0219] Based on the passage of time using a network timing protocol or GPS timing signal or other time reference, a clock synchronization signal can be calculated. For example, a reference frequency can be found from an internet source. Based on the passage of time using NTP, a clock synchronization signal can be calculated. This synchronization signal can then be sent to other sensors.

[0220] 7.4. Location Awareness Sensor Parameters

[0221] In some embodiments, the sensor may obtain location information. In this regard, the sensor may include or access data from a positioning system such as a Global Positioning System (GPS), thereby allowing the sensor to obtain geographic location information regarding the sensor's current location. In some embodiments, the sensor may be included in or connected to a smart device (e.g., a smartphone, tablet, smartwatch, etc.). Thus, the sensor may receive its geographic location information from the smart device. Timing information may also be retrieved via a GPS receiver, and wireless synchronization may be permitted (assuming sufficient GPS signal is available).

[0222] Based on the input of geographic location information, the sensor can then ensure that it operates within the agreed spectrum limits for the current geographic region where the sensor is located. Alternatively, if the sensor's possible parameter control set cannot operate the sensor within the agreed spectrum limits for the geographic region where the sensor is located, the sensor can be automatically deactivated. Thus, one or more sensors can coexist with local radio frequency regulations and with each other.

[0223] 7.5. Low Power State

[0224] If no motion is detected for a predetermined amount of time, the sensor can switch to a low-power search mode (or even a sleep or off mode). In this regard, the sensor can be integrated into body-worn devices such as pendants, chest straps, bracelets, watches, hats, and other such devices. Additionally, the sensor can be built directly into existing electronic devices such as smart watches, smartphones, Internet of Things (IoT) devices, and the like.

[0225] Thus, the sensor can be programmed to switch to a low power search mode when the device in which the sensor is integrated is not in use (e.g., if no motion is detected). For example, a sensor integrated into a pendant may be placed on a dressing table. Since the user is not wearing the pendant, the sensor may not detect motion. Therefore, the range of the sensor can be adjusted by reducing the output power, frequency and / or duration of the pulses to reduce the overall power consumption. In addition, the adjustment can be programmed to be within an agreed range. Although sensors integrated into devices are described, stand-alone sensors may also be programmed to switch to a low power search mode when the sensor cannot detect motion. Therefore, by reducing the RF transmit power of one or more sensors, the low power condition can further aid coexistence.

[0226] 7.6. Security

[0227] The sensors can also be used in security sensing applications to detect unauthorized physiological patterns in a detection area (e.g., the intrusion of one or more people) and sound an alarm (or send a control signal to a processor). It can be seen that in security applications, many such sensors can be co-located in a building, so RF sensor coexistence is very important. When the user is away during the day, one or more sleep sensors can also be reconfigured by the control system to serve as nodes or sensors in an intruder (burglar) alarm system (e.g., to detect an intruder in the bedroom).

[0228] 7.7. Processing

[0229] Processing signals (e.g., signals received by a sensor) can be performed by a processor on a sensor printed circuit board assembly (PCBA). Such a PCBA can also allow communication with a remote processor (e.g., a microprocessor on a motherboard) via analog and / or digital links.

[0230] In embodiments with digital sensors, the signals can be digitized and transmitted via a wireless or wired connection. Digitization can be performed at high resolution and / or sampling rate, and the sensor signals themselves (e.g., in-phase (I) and quadrature (Q) streams, or streams before or without I and Q separation) can be transmitted to a single or multiple processors. In addition, each channel of transmitted information can also include information about the current or recent center frequency, relative changes in center frequency, the lookup table location being used, etc.

[0231] By minimizing the number of components on one or more sensors, the number of components required to implement a multi-sensor system can be reduced. For example, in an operating environment such as a home, apartment building, hotel, office, hospital, or nursing home where multiple sensors are used, the system can leverage existing data links and / or data processing capabilities available in a wider range of system implementations to achieve the desired motion and physiological sensing. In one example, the sensors can transmit their respective signals to a remotely located, separately packaged processor capable of processing multiple sensor signals simultaneously.

[0232] Optionally, the digitized sensor signals can be transcoded into audio frequencies so that existing audio processing accelerators and routines can be utilized to detect specific motion patterns.

[0233] Additionally, while the primary focus of the described technology is associated with applications for detecting breathing, sleep, and heart rate, it is equally suitable for detecting other movements of the human body (or animal, if equipped with sensors).

[0234] Unless the context clearly dictates otherwise, and where a range of values ​​is provided, it is understood that every intervening value between the upper and lower limits of the range (to the tenth of the unit of the lower limit) and any other stated or intervening value within the stated range are encompassed within the technology. The upper and lower limits of these intervening ranges that may independently be included in the intervening range are also encompassed within the technology, except for any specifically excluded limit in the stated range. Where a stated range includes one or both limits, ranges excluding the included one or both limits are also encompassed within the technology.

[0235] Furthermore, where a value or values ​​are stated herein as being implemented as part of a technology, it should be understood that these values ​​may be approximate unless otherwise indicated and that these values ​​may be used with any significant digits as appropriate, as the actual technology implementation may allow or require.

[0236] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this technology belongs. Although any methods and materials similar or equivalent to those described herein can also be used in the practice or testing of this technology, a limited number of exemplary methods and materials are described herein.

[0237] When a particular material is identified as being preferred for use in constructing a component, obvious alternative materials having similar properties may be used as substitutes. Furthermore, unless otherwise specified, any and all components described herein should be understood to be capable of being manufactured, and as such, may be manufactured together or separately.

[0238] It must be noted that as used herein and in the appended claims, the singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0239] All publications mentioned herein are incorporated by reference to disclose and describe the methods and / or materials that are the subject of these publications. The publications discussed herein are provided solely for their disclosure prior to the filing date of this application. Anything herein should not be construed as admitting that the technology is not entitled to release such publications in advance by virtue of prior inventions. In addition, the dates of the publications provided may differ from the actual publication dates and may require independent confirmation.

[0240] Furthermore, when interpreting this disclosure, all terms should be interpreted in the broadest reasonable manner consistent with the context. Specifically, the terms "comprise" and "include" should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present or utilized or combined with other elements, components, or steps not explicitly referenced.

[0241] The subject headings used in the detailed description are included only for the reader's convenience and should not be used to limit the subject matter found in the entire disclosure or claims. The subject headings should not be used to interpret the scope of the claims or claim limitations.

[0242] Although the technology herein has been described with reference to specific embodiments, it should be understood that these embodiments are merely illustrative of the principles and applications of the technology. In some cases, terms and symbols may imply specific details that are not necessary for practicing the technology. For example, although the terms "first" and "second" may be used, unless otherwise specified, they are not intended to indicate any order, but may be used to distinguish different elements. In addition, although the processing steps in the method can be described or illustrated in sequence, such ordering is not required. Those skilled in the art will recognize that the ordering can be modified and / or aspects thereof can be implemented simultaneously or even synchronously.

[0243] It will be understood, therefore, that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the present technology. It will be further understood that, unless otherwise indicated, any reference herein to subject matter known in the art does not constitute an admission that such subject matter is generally known to one skilled in the art to which the present technology relates.

[0244] Parts List:

[0245] Testing equipment 100

[0246] Testing equipment 102

[0247] Sensor 300

[0248] Sensor 302

[0249] RF pulse 310

[0250] RF Pulse 312

[0251] Sensor 402

[0252] Oscillator 404

[0253] Pulse generator 408

[0254] Periodic sine amplitude envelope 600

[0255] Signal 602

[0256] Signal 700

[0257] Signal 702

[0258] Synthesized receiver RF signal 704

[0259] Sensor 800

[0260] Second active source 802

[0261] Object 804

[0262] RF signal 806

[0263] Signal 808

[0264] Main sensor 1201

[0265] Slave sensor 1202

[0266] Red signal 1204

[0267] Main sensor circuit 1301

[0268] Slave sensor circuit 1302

[0269] Housing unit 1400

[0270] Signal 1402

[0271] Signal 1404

[0272] Sensor 1406

[0273] Sensor 1408

Claims

1. A physiological motion sensor configured to operate in a multi-sensor configuration and for co-operation with a respiratory therapy device, the respiratory therapy device providing an automatic treatment response based on analysis of a physiological characteristic sensed by the physiological motion sensor, the physiological motion sensor comprising: a transmitter configured to transmit a radio frequency signal; as well as a receiver configured to receive a reflection signal of the radio frequency signal to detect motion of a reflective surface; wherein the physiological motion sensor is configured for sensing in the vicinity of another physiological motion sensor to mitigate interference between the physiological motion sensor and the other physiological motion sensor, wherein the physiological motion sensor is configured to detect temperature changes, and Based on the detected temperature change, the physiological motion sensor is configured to initiate polling with the other physiological motion sensor to adjust operation of at least one of the physiological motion sensor and the other physiological motion sensor. 2 . The physiological motion sensor of claim 1 , wherein the adjusting operation of at least one of the physiological motion sensor and the another physiological motion sensor comprises adjusting a frequency for operation. 3 . The physiological motion sensor of claim 2 , wherein the frequency for operation is a center frequency of at least one of the physiological motion sensor and the another physiological motion sensor.

4. A radio frequency physiological motion sensor configured to operate in proximity to another radio frequency physiological motion sensor, the radio frequency physiological motion sensor comprising: a radio frequency transmitter configured to transmit a radio frequency signal; as well as a receiver configured to receive a reflection signal of the transmitted radio frequency signal to detect motion of the reflective surface; wherein the radio frequency transmitter and the receiver are configured to sense one or more physiological characteristics of the user including at least respiratory motion; wherein the radio frequency physiological motion sensor is configured to mitigate interference emitted from the other radio frequency physiological motion sensor; Wherein at least one of the radio frequency physiological motion sensor and the another radio frequency physiological motion sensor is configured to operate in a low power mode when no motion is detected. The radio frequency physiological motion sensor according to claim 4 , wherein the low power mode comprises a low power search mode. 6 . The radio frequency physiological motion sensor according to claim 4 , wherein the low power mode comprises reducing the output power, frequency and / or duration of the transmitted pulses.

7. A radio frequency physiological motion sensor configured to operate in a multi-sensor configuration, the radio frequency physiological motion sensor comprising: a radio frequency transmitter configured to transmit a radio frequency signal; as well as a receiver configured to receive a reflection signal of the transmitted radio frequency signal to detect motion of the reflective surface; The radio frequency transmitter and the receiver are configured to sense one or more physiological characteristics of a user; The RF transmitter is configured to operate with another RF physiological motion sensor near the RF physiological motion sensor to mitigate interference between a transmitted signal from the RF physiological motion sensor and a transmitted signal from the other RF physiological motion sensor by ramp dithering according to a linear ramp function. 8 . The radio frequency physiological motion sensor according to claim 7 , wherein the linear ramp function generates associated jitter in the pulse repetition interval and the pulse width.

9. The radio frequency physiological motion sensor according to claim 7 or 8, wherein the radio frequency physiological motion sensor comprises a synchronous ramp dithering circuit.

10. A radio frequency physiological motion sensor configured to operate in a multi-sensor configuration, the radio frequency physiological motion sensor comprising: a radio frequency transmitter configured to transmit a radio frequency signal; as well as a receiver configured to receive a reflection signal of the transmitted radio frequency signal to detect motion of the reflective surface; The radio frequency transmitter and the receiver are configured to sense one or more physiological characteristics of a user; The RF transmitter is configured to operate with another RF physiological motion sensor in the vicinity of the RF physiological motion sensor to mitigate interference between a transmitted signal from the RF physiological motion sensor and a transmitted signal from the another RF physiological motion sensor, wherein the RF physiological motion sensor and the another RF physiological motion sensor are configured to transmit RF signals at an angle of at least ninety degrees to each other. 11 . The radio frequency physiological motion sensor according to claim 10 , wherein the radio frequency physiological motion sensor and the another radio frequency physiological motion sensor are in a single housing. 12 . The radio frequency physiological motion sensor according to claim 10 , wherein the radio frequency physiological motion sensor and the another radio frequency physiological motion sensor are synchronized through a direct connection.

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