Multi-user respiration monitoring method and system based on time modulation array

Abstract

The invention discloses a multi-user respiration monitoring method and system based on a time modulation array, and belongs to the technical field of non-contact respiration monitoring, and the method comprises the steps: controlling an array element periodic switch of a uniform linear array to transmit a radar signal through a TMA in a pulse shift modulation mode, and receiving a radar echo signal reflected by a target. According to the characteristic that TMA can generate a fundamental component and infinite harmonic components, a digital down-conversion filter is constructed to extract the harmonic components of radar echo signals, and the stable harmonic components are obtained through the frequency offset compensation technology. Furthermore, the phase of the harmonic component is calculated by adopting an improved differential cross multiplication algorithm, so that the time domain respiration information of the user is obtained. According to the method, the complexity of the feed network is reduced, meanwhile, accurate multi-user respiration monitoring is achieved, and the method is suitable for multi-user respiration monitoring requirements in various environments.

Description

Technical Field

[0001] The present invention relates to the technical field of non-contact respiratory monitoring, and in particular to a multi-user respiratory monitoring method and system based on a time modulation array. Background Art

[0002] Breathing, one of the most important human life activities, not only maintains normal physiological functions but is also closely related to a person's physical and mental health. Studying respiratory movements is crucial for understanding human physical and mental health. Currently, existing respiratory monitoring methods are primarily categorized into contact and non-contact methods.

[0003] In contact respiratory monitoring methods, various wearable devices are used for respiratory monitoring, such as smart mattresses, respiratory belts with built-in fiber optic sensors, smart pillows with embedded pressure sensors, and smart integrated textile clothing. However, since it requires users to wear the device at all times, people may be unwilling to wear it, unable to wear it, or forget to wear it. This limits the long-term continuous respiratory monitoring of wearable devices in daily environments. In contrast, non-contact respiratory monitoring methods directly obtain respiratory information without contacting the user, providing users with great convenience and comfort. Depending on the implementation method, it is mainly divided into monitoring methods based on optical signals, acoustic signals, and wireless signals.

[0004] Monitoring methods based on optical signals are susceptible to factors such as illumination and occlusion, and pose significant privacy concerns. Monitoring methods based on acoustic signals are susceptible to interference from ambient noise and also present privacy issues. Monitoring methods based on wireless signals, with their low cost, passivity, and privacy protection, offer a new perspective for contactless respiratory monitoring. Portable, low-cost, and highly reliable multi-person respiratory monitoring is an important development direction for wireless signal-based monitoring methods.

[0005] Currently, there are four main approaches to multi-person respiration monitoring based on wireless signals: distance separation, angle separation, frequency separation, and blind signal separation. Distance separation relies on the bandwidth of the wireless signal. If the distance between two targets is the same or smaller than the distance resolution, it cannot be distinguished. Angle separation decouples the signals of individual targets based on their relative angles. This method relies on the spatial resolution of the wireless signal, which is inversely proportional to the number of antennas. Frequency separation estimates the respiratory frequency of each target based on the frequency spectrum, taking into account individual differences in breathing rate. However, this method cannot address the issue of multiple targets having identical breathing rates. While blind signal separation can overcome the limitations of these approaches to some extent, it requires a predetermined number of people, and the separated signals are difficult to match to each target. In multi-person monitoring scenarios, if a single individual exhibits abnormal breathing, it is difficult to immediately identify the individual. Therefore, a stable and reliable multi-user respiration monitoring technology is needed. Summary of the Invention

[0006] In response to the problems existing in the prior art, the present invention provides a multi-user respiration monitoring method and system based on a time modulation array, which not only reduces the complexity of the feeding network but also realizes accurate multi-user respiration monitoring.

[0007] The present invention is achieved through the following technical solutions: A multi-user respiration monitoring method based on a time modulation array comprises the following steps: Step 1: Obtain radar echo signal; The radar echo signal is a radar signal transmitted by the TMA in a pulse shift (PS) modulation mode to control the periodic switching of the array elements of the uniform linear array, and the radar echo signal is generated by the radar signal being reflected by the target and received through a single channel; Step 2: Based on the characteristic of TMA that can generate a fundamental component and an infinite number of harmonic components, a digital down-conversion filter is constructed, and the harmonic component A of the radar echo signal is extracted using the filter; the radar echo signal in a static environment is mixed to obtain a frequency-shifted harmonic component B, and the phase slope of the harmonic component B is determined based on the frequency-shifted harmonic component B. The phase slope is used to compensate the frequency offset of the harmonic component A to obtain a stable harmonic component; Step 3: Determine the phase of each harmonic component based on the stable harmonic component to obtain the user's time-domain breathing information.

[0008] Preferably, the TMA in step 1 controls the periodic switching of the elements of the uniform linear array to transmit radar signals in a pulse shift modulation manner. The expression of the radar signal is as follows:

[0009] Where, is the direction of electromagnetic wave radiation; is the signal carrier frequency; is the time modulation function of the nth RF switch; is the wave number in free space, ; is the signal wavelength, ; is the antenna spacing, ; is the propagation speed of electromagnetic waves in free space.

[0010] Preferably, the time modulation function of the TMA in pulse shift modulation mode is as follows: The time modulation function is determined according to the modulation period, and the time modulation function is expanded using the Fourier series to obtain the final time modulation function, which is expressed as follows:

[0011] Where, For the The coefficients of the subharmonic components; is the modulation frequency, ; is the modulation period.

[0012] Preferably, the method for acquiring the radar echo signal is as follows: After the radar signal is reflected by the target object, it undergoes time modulation to obtain a radar echo signal, which is the sum of a fundamental wave component and an infinite number of harmonic components.

[0013] Preferably, the method for extracting the harmonic component A of the radar echo signal according to the filter in step 2 is as follows: The received radar echo signal is mixed with different harmonics in sequence, and then the harmonic component A of the radar echo signal is obtained through a low-pass filter.

[0014] 6. The multi-user respiration monitoring method based on a time modulation array according to claim 1, wherein the method for obtaining the stable harmonic component in step 2 is as follows: The received radar echo signal is mixed with the ideal harmonic component and then passed through a low-pass filter to obtain the harmonic component B with a certain frequency offset. The phase slope of harmonic component B is calculated using a linear regression algorithm. The phase slope is used to compensate for the frequency offset of harmonic component A in the mixing stage, so that a stable harmonic component A can be obtained.

[0015] Preferably, in step 3, an improved differential cross-multiplication algorithm is used to calculate the phase of the harmonic component.

[0016] Preferably, the phase calculation method of the harmonic component is as follows:

[0017] Where, n is the length of the harmonic component, I is the real part of the obtained harmonic component, Q is the imaginary part of the obtained harmonic component.

[0018] A multi-user respiratory monitoring system based on a time modulation array, comprising: Signal acquisition module, used to obtain radar echo signals; The radar echo signal is a radar signal transmitted by the TMA in a pulse shift modulation mode to control the periodic switching of the array elements of the uniform linear array, and the radar echo signal is generated after the radar signal is reflected by the target and received through a single channel; The compensation module is used to construct a digital down-conversion filter based on the characteristic of the TMA that can generate a fundamental component and an infinite number of harmonic components. The harmonic component A of the radar echo signal is extracted using the filter. The radar echo signal in a static environment is mixed to obtain a frequency-shifted harmonic component B. The phase slope of the harmonic component B is determined based on the frequency-shifted harmonic component B. The phase slope is used to compensate the frequency offset of the harmonic component A to obtain a stable harmonic component. The monitoring module is used to determine the phase of each harmonic component based on the stable harmonic component to obtain the user's time-domain breathing information.

[0019] An electronic device, comprising: Memory for storing computer programs; A processor is configured to execute the computer program to implement the steps of the multi-user respiration monitoring method based on a time modulation array.

[0020] Compared with the prior art, the present invention has the following beneficial technical effects: This application proposes a multi-user respiration monitoring method based on a time-modulated array (TMA). First, leveraging the TMA's ability to generate a fundamental component and an infinite number of harmonic components, a digital down-conversion filter is constructed to extract the harmonic components of the radar echo signal. This not only effectively avoids interference from ambient noise but also makes radar signal processing more efficient and accurate. By analyzing the harmonic components, the user's respiration information, including key parameters such as respiratory rate and depth, can be accurately acquired. Secondly, frequency offset compensation technology is used to further improve the stability of the harmonic components. Because the modulation frequency generated by the RF switch controller may deviate from the ideal modulation frequency, this technical solution uses a linear regression algorithm to calculate the phase slope of each harmonic component and compensate for the frequency offset. This ensures the accuracy and reliability of the radar echo signal in subsequent processing. Furthermore, a modified differential cross-multiplication (MDACM) algorithm is used to calculate the phase of the harmonic components. The application of the MDACM algorithm makes phase calculation more accurate and faster, thereby improving the real-time and accuracy of respiratory monitoring; this method utilizes the harmonic characteristics of TMA, constructs a digital down-conversion filter, performs frequency offset compensation, and uses the MDACM algorithm to calculate the phase, achieving non-contact, high-precision, and real-time monitoring of multi-user respiratory information.

[0021] This application also proposes a multi-user respiratory monitoring system based on a time modulation array, an electronic device and a computer storage medium, which have all the advantages of the above-mentioned multi-user respiratory monitoring method based on a time modulation array. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0023] Figure 1 Schematic diagram of the flow of the multi-user respiration monitoring method based on the time modulation array of the present invention; Figure 2 Schematic diagram of the architecture of a multi-user respiratory monitoring system based on a time modulation array according to the present invention; Figure 3 This is a schematic diagram of the PS time modulation array based on the present invention; Figure 4 This is a schematic diagram of the PS time modulation function of the present invention; Figure 5 The radiation pattern of the PS time modulation array of the present invention is as follows; Figure 6 This is a diagram of the breathing monitoring results of a single person according to the present invention; Figure 7 This is a diagram of the respiratory monitoring results of multiple people in the present invention. DETAILED DESCRIPTION

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present application more clear, the technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Generally, the components of the embodiments of the present application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0025] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application for protection, but merely represents selected embodiments of the present application. All other embodiments obtained by persons of ordinary skill in the art based on the embodiments in the present application without creative work are within the scope of protection of the present application.

[0026] To address the problem of multi-user respiration monitoring based on wireless signals, this application provides a single-channel, low-complexity multi-user respiration monitoring method. Compared to multi-channel arrays, a single-channel time modulated array (TMA) is used as the transmit array. This architecture offers the advantages of low cost, high reliability, and ease of deployment.

[0027] A multi-user respiration monitoring method based on a time modulation array comprises the following steps: Step 1: Obtain radar echo signal; The radar echo signal is a radar echo signal generated by transmitting a radar signal through the TMA and reflected by the target and received through a single channel; Among them, TMA uses pulse shifting (PS) modulation to control the periodic switching of the array elements of the uniform linear array to transmit radar signals.

[0028] PS modulation means that the RF switching system of TMA is controlled by a switch.

[0029] Step 2: Based on the TMA's ability to generate a fundamental component and an infinite number of harmonic components, a digital down conversion (DDC) filter is constructed. Harmonic component A of the radar echo signal is extracted using the filter. The radar echo signal in a static environment is mixed to obtain a frequency-shifted harmonic component B. The phase slope of harmonic component B is determined based on the frequency-shifted harmonic component B. During the mixing stage, the phase slope is used to compensate for the frequency offset of harmonic component A to obtain a stable harmonic component.

[0030] In this step, based on the characteristic of TMA that it can generate a fundamental component and an infinite number of harmonic components, a digital down-conversion filter is constructed to extract the harmonic components of the radar echo signal.

[0031] Each DDC filter is composed of three parts: a mixer, a low-pass filter (LPF), and downsampling. First, the received radar echo signal is mixed with different harmonic components by the mixer to move the spectrum of the received signal to the baseband; then the interference of other harmonic components is removed by the LPF to obtain the required harmonic components; finally, downsampling is used to reduce the amount of data, reduce the overhead of data storage and signal processing, and obtain the fundamental component and harmonic component of the received radar echo signal. However, since the modulation frequency generated by the RF switch controller deviates from the ideal modulation frequency, the resulting frequency offset affects the extraction of the harmonic components, so it is necessary to estimate and compensate for the frequency offset. The estimation and compensation of frequency offset is to estimate the phase slope (angular frequency) of each harmonic component by linear regression, according to which the frequency is equal to the angular frequency divided by , the frequency offset is calculated and compensated in the mixing stage to obtain a stable harmonic component.

[0032] Step 3: Extract the phase of each harmonic component based on the stable harmonic component. The obtained phase is the user's time-domain breathing information at the corresponding harmonic component. The phase of each harmonic component is solved using the modified differential and cross-multiply (MDACM) algorithm.

[0033] This multi-user respiration monitoring method based on a time-modulated array provides a single-channel Doppler radar architecture for the time-modulated array, effectively simplifying the complexity of the multi-channel array feed network. Furthermore, a harmonic extraction method using a digital down-conversion filter reliably restores the time-modulated array to a traditional uniform linear array. The proposed frequency offset compensation method achieves a stable harmonic phase, improving the accuracy of contactless respiration detection.

[0034] Example 1 A multi-user respiration monitoring method based on a time modulation array comprises the following steps: Step 1: Build a multi-user respiratory monitoring device with wireless signals.

[0035] See Figure 1 and 2 ,1) Using the open source GNU Radio framework to configure the USRP B210 device as a ,Continuous Wave Doppler radar; The GNU Radio framework is used to build Software Defined Radio (SDR) and signal processing systems, and implements flexible signal processing flows through graphical programming or code scripts.

[0036] The USRP B210 device is a high-performance software-defined radio (SDR) device.

[0037] 2) Deploy a TMA on the USRP B210 transmitter to transmit radar signals. The TMA consists of four identical 2.4 GHz microstrip Yagi antennas, a single-pole, four-throw RF switch (HMC7992), and an STM32F193C8T6 (STM32) microprocessor. TMA is a time-modulated array (TMA) technology that achieves beamforming and directionality control by periodically controlling the switching time of antenna elements.

[0038] 3) Connect a 2.4 GHz microstrip Yagi antenna to the receiving end of the USRP B210 device to receive the radar echo signal.

[0039] Step 2: Orient the four transmitting antennas and the receiving antenna in the TMA toward the user, with the height of the transmitting and receiving antennas above the ground approximately equal to the user's chest. By controlling the output level of the STM32 microprocessor's general purpose input / output (GPIO) ports, the RF switches are switched from right to left, sending radar signals to the user and receiving radar echo signals through the receiving antennas.

[0040] See Figure 3 and 4 ,1) The radar signal is transmitted through TMA, which is generated by periodically modulating the uniform linear array and can be expressed as: (1) In the formula is the direction of electromagnetic wave radiation; is the signal carrier frequency; is the time modulation function of the nth RF switch; , is the wave number of free space; , is the signal wavelength; , is the antenna spacing; , is the propagation speed of electromagnetic waves in free space.

[0041] In this embodiment, a pulse shifting method is used to perform time array modulation, and each antenna unit switches between ON and OFF states in sequence with a period of 1 / N.

[0042] Time modulation function It can be expressed as: (2) in, is the modulation period. Since the modulation function It is periodic and can be expressed as follows after Fourier series expansion: (3) Where, is the modulation frequency. Subharmonic coefficients It can be expressed as: (4) Therefore, the radar signal transmitted by TMA can be expressed as: (5) 2) Radar echo signal is a continuous wave signal emitted by the radar transmitter and reflected by objects including the user and returned to the receiver. After time modulation, the radar echo signal is the sum of the fundamental component and an infinite number of harmonic components, and the frequency interval between adjacent harmonics is .

[0043] According to formulas (4) and (5), the direction of the fundamental component is 0°, and different harmonic components point to different directions. The k-th order harmonic component is: (6) Where, and Respectively represent the target object in The attenuation coefficient and delay introduced in the direction. is determined by the chest wall displacement caused by breathing, where is the chest wall displacement distance, Represents the respiratory rate, Indicates the initial phase offset.

[0044] Step 3: Based on the characteristic of TMA that it can generate a fundamental component and an infinite number of harmonic components, a digital down-conversion (DDC) filter is constructed to extract the harmonic component A of the radar echo signal. The radar echo signal in a static environment is mixed to obtain the frequency-shifted harmonic component B. The phase slope of the harmonic component B is determined according to the frequency-shifted harmonic component B. The phase slope is used to compensate the frequency offset of the harmonic component A in the mixing stage to obtain a stable harmonic component.

[0045] 1) To obtain the harmonic components, the received radar echo signal is mixed with different harmonics in turn, and then the harmonic components of the radar echo signal are obtained through a low-pass filter. The method is as follows: The digital down-conversion filter consists of three parts: mixer, low-pass filter and down-sampling.

[0046] First, the received radar echo signal is mixed with the k-th order harmonic component in sequence using a mixer, and the spectrum of the received radar echo signal is moved to the baseband. Then, the interference of other harmonic components is removed by a low-pass filter to obtain the desired harmonic component; Secondly, downsampling is used to reduce the data volume and the overhead of data storage and signal processing, and the harmonic component A of the received radar echo signal is obtained.

[0047] The harmonic component A includes -1 order harmonic component, 1 order harmonic component and fundamental wave component (0 order harmonic component). Figure 5 .

[0048] 2) Using the radar echo signal in a static environment, determine the phase slope of the harmonic component in the static environment, and perform frequency offset compensation on the harmonic component A according to the phase slope to obtain a stable harmonic component. The method is as follows: It should be noted that the modulation frequency generated by the STM32 microprocessor deviates from the ideal modulation frequency. The resulting frequency offset affects the extraction of the harmonic component A. Therefore, the frequency offset is estimated and compensated.

[0049] A static environment refers to an environment without a target object, that is, an environment without a target object that reflects signals in the same environment as step 1).

[0050] First, a 30-second radar echo signal is collected in a static environment. The received radar echo signal is then mixed with the ideal harmonic component, and then passed through a low-pass filter to obtain the harmonic component B with a certain frequency offset.

[0051] The low-pass filter is a Butterworth low-pass filter with a passband of 0 to 200 Hz designed using the Filter Designer application of Matlab.

[0052] Secondly, if the k-th harmonic has a frequency offset ,because The phase of the harmonic component changes linearly with time, so the phase slope of each harmonic component B is calculated by linear regression ,but .

[0053] Finally, in the mixing stage of the DDC, the phase slope is used to frequency shift the harmonics. By compensating, stable harmonic components can be obtained.

[0054] Step 4: TMA makes different harmonic components have different spatial distributions. By calculating the phase of each harmonic component based on the stable harmonic component, the user's time-domain breathing information on the harmonic component can be obtained.

[0055] The various harmonic components are solved using the improved differential cross multiplication (MDACM) algorithm.

[0056] Specifically, since each extracted harmonic component is a complex vector, the real part of the complex vector is called the I signal and the imaginary part is called the Q signal. The I / Q signal is input into the MDACM algorithm to obtain the final phase, which can be expressed as: (7) The phase obtained in this way is the time-domain breathing information of the user on the corresponding harmonic component.

[0057] Figure 6 This is the result of single-person breathing monitoring in the present invention; in the single-user breathing monitoring experiment, we require the user to sit at -30°, 0° and 30° relative to the horizontal direction of the TMACW radar, as shown in the figure. Figure 6 (a) shows the distance between the target and the radar. The distance between the target and the radar is 1.5 meters. Each experiment collects 60 seconds of data. In order to intuitively show the fluctuation degree of each harmonic component breathing signal, the phase of the obtained harmonic component is normalized: (8) in For the k ( ) The peak-to-peak value of the subharmonic component. The normalized time domain normal breathing waveform is as follows Figure 6 (b), 6(c) and 6(d). Figure 5 It can be seen that the -1 harmonic component points to -30°. When the user is at -30°, the breathing signal of the -1 harmonic component is more obvious than other components, such as Figure 6 (b) shows that there are also weak breathing signals in the fundamental component and the first-order harmonic component. This is because the user cannot be regarded as a point target. Assuming that the user's body width is 40 cm and the distance from the radar is 1.5 m, the angular width of the user relative to the radar is about 15°, so the signal in the desired direction may leak into other harmonic components. Similarly, the time domain breathing waveforms of the user sitting at 0° and 30° are shown as follows: Figure 6 (c) and Figure 6 (d) shown.

[0058] Figure 7 This is the result of multi-user breathing monitoring in the present invention. In the multi-user breathing monitoring experiment, user A and user B are required to sit at -30° and 30° respectively. Figure 7(a) The distance between the TMACW radar and the user is also 1.5 meters. The normalized time domain breathing waveforms of the two users measured simultaneously are shown as follows: Figure 7 As shown in (b). It can be found that the proposed method can simultaneously monitor the respiratory signals of two users with similar respiratory frequencies, and since different users have different chest wall displacements during breathing, the amplitudes of their respiratory signals are also different. In addition, the abnormal breathing monitoring performance of the proposed method is further explored. In this experiment, user A is required to hold his breath randomly within 0 ~ 30 s to simulate a apnea event, and subject B is required to simulate a apnea event within 30 ~ 60 s. The normalized time domain abnormal breathing waveforms of the two users measured at the same time are shown as follows: Figure 7 (c) is shown. Figure 7 In (c), it can be found that user A had a apnea event within 15 to 21 seconds, and user B had a apnea event within 42 to 48 seconds.

[0059] Correspondingly, the present application also provides a multi-user respiratory monitoring system based on a time modulation array, comprising: Signal acquisition module, used to obtain radar echo signals; The radar echo signal is a radar signal transmitted by the TMA in a pulse shift modulation mode to control the periodic switching of the array elements of the uniform linear array, and the radar echo signal is generated after the radar signal is reflected by the target and received through a single channel; The compensation module is used to construct a digital down-conversion filter based on the characteristic of the TMA that can generate a fundamental component and an infinite number of harmonic components. The harmonic component A of the radar echo signal is extracted using the filter. The radar echo signal in a static environment is mixed to obtain a frequency-shifted harmonic component B. The phase slope of the harmonic component B is determined based on the frequency-shifted harmonic component B. The phase slope is used to compensate the frequency offset of the harmonic component A to obtain a stable harmonic component. The monitoring module is used to determine the phase of each harmonic component based on the stable harmonic component to obtain the user's time-domain breathing information.

[0060] It should be noted that in the several embodiments provided in this application, it should be understood that the disclosed devices and methods can be implemented in other ways. For example, the device embodiments described above are merely schematic. For example, the division of each module is only a logical function division. There may be other division methods in actual implementation. For example, multiple modules can be combined or integrated into another device, or some features can be ignored or not executed. The modules described as separate components may or may not be physically separated. The components displayed as modules may be one physical unit or multiple physical units, that is, they may be located in one place, or they may be distributed in multiple different places. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment.

[0061] In addition, the modules in the various embodiments of the present invention may be integrated into a single processing unit, each module may exist physically separately, or two or more modules may be integrated into a single unit. The aforementioned integrated units may be implemented in the form of hardware or software functional units.

[0062] An electronic device provided in an embodiment of the present application includes a memory and a processor. The memory stores a computer program, and when the processor executes the computer program, the steps of the multi-user respiration monitoring method based on a time modulation array as described in any of the above embodiments are implemented.

[0063] Another electronic device provided in an embodiment of the present application may further include: an input port connected to the processor for transmitting multimodal data collected by an external acquisition device to the processor; a display unit connected to the processor for displaying the processing results of the processor to the outside world; and a communication module connected to the processor for enabling communication between the electronic device and the outside world. The display unit may be a display panel, a laser scanning display, etc.; the communication method adopted by the communication module includes but is not limited to mobile high-definition link technology (HML), universal serial bus (USB), high-definition multimedia interface (HDMI), wireless connection (including wireless fidelity technology (WiFi), Bluetooth communication technology, low-power Bluetooth communication technology, and communication technology based on IEEE802.11s).

[0064] An embodiment of the present application provides a computer-readable storage medium, in which a computer program is stored. When the computer program is executed by a processor, the steps of the multi-user respiration monitoring method based on a time modulation array as described in any of the above embodiments are implemented.

[0065] For descriptions of the relevant portions of the time-modulated array-based multi-user respiration monitoring system, electronic device, and computer-readable storage medium provided in the embodiments of this application, please refer to the detailed description of the corresponding portions of the time-modulated array-based multi-user respiration monitoring method provided in the embodiments of this application, and these descriptions are omitted here. Furthermore, portions of the technical solutions provided in the embodiments of this application that align with the implementation principles of corresponding technical solutions in the prior art are not described in detail to avoid redundant description.

[0066] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A multi-user respiration monitoring method based on a time modulation array, characterized in that: The following steps are involved: Step 1: Obtain radar echo signal; The radar echo signal is a radar signal transmitted by the TMA in a pulse shift modulation mode to control the periodic switching of the array elements of the uniform linear array, and the radar echo signal is generated after the radar signal is reflected by the target and received through a single channel; Step 2: Based on the characteristic of TMA that can generate a fundamental component and an infinite number of harmonic components, a digital down-conversion filter is constructed, and the harmonic component A of the radar echo signal is extracted using the filter; the radar echo signal in a static environment is mixed to obtain a frequency-shifted harmonic component B, and the phase slope of the harmonic component B is determined based on the frequency-shifted harmonic component B. The phase slope is used to compensate the frequency offset of the harmonic component A to obtain a stable harmonic component; Step 3: Determine the phase of each harmonic component based on the stable harmonic component to obtain the user's time-domain breathing information.

2. The multi-user respiration monitoring method based on a time modulation array according to claim 1, characterized in that: In step 1, the TMA controls the periodic switching of the elements of the uniform linear array using pulse shift modulation to transmit radar signals. The expression of the radar signal is as follows: Where, is the direction of electromagnetic wave radiation; is the signal carrier frequency; is the time modulation function of the nth RF switch; is the wave number in free space, ; is the signal wavelength, ; is the antenna spacing, ; is the propagation speed of electromagnetic waves in free space.

3. The multi-user respiration monitoring method based on a time modulation array according to claim 2, characterized in that: The time modulation function of the TMA in pulse shift modulation mode is as follows: The time modulation function is determined according to the modulation period, and the time modulation function is expanded using the Fourier series to obtain the final time modulation function, which is expressed as follows: Where, For the The coefficients of the subharmonic components; is the modulation frequency, ; is the modulation period.

4. The multi-user respiration monitoring method based on a time modulation array according to claim 3, characterized in that: The method for obtaining the radar echo signal is as follows: After the radar signal is reflected by the target object, it undergoes time modulation to obtain a radar echo signal, which is the sum of a fundamental wave component and an infinite number of harmonic components.

5. The multi-user respiration monitoring method based on a time modulation array according to claim 1, characterized in that: The method for extracting the harmonic component A of the radar echo signal according to the filter in step 2 is as follows: The received radar echo signal is mixed with different harmonics in sequence, and then the harmonic component A of the radar echo signal is obtained through a low-pass filter.

6. The multi-user respiration monitoring method based on a time modulation array according to claim 1, characterized in that: The method for obtaining the stable harmonic components described in step 2 is as follows: The received radar echo signal is mixed with the ideal harmonic component and then passed through a low-pass filter to obtain the harmonic component B with a certain frequency offset. The phase slope of harmonic component B is calculated using a linear regression algorithm. The phase slope is used to compensate for the frequency offset of harmonic component A in the mixing stage, so that a stable harmonic component A can be obtained.

7. The multi-user respiration monitoring method based on a time modulation array according to claim 1, characterized in that: In step 3, an improved differential cross-multiplication algorithm is used to calculate the phase of the harmonic component.

8. The multi-user respiration monitoring method based on a time modulation array according to claim 7, characterized in that: The phase calculation method of the harmonic component is as follows: Where, n is the length of the harmonic component, I is the real part of the obtained harmonic component, Q is the imaginary part of the obtained harmonic component.

9. A multi-user respiratory monitoring system based on a time modulation array, characterized in that: include: Signal acquisition module, used to obtain radar echo signals; The radar echo signal is a radar signal transmitted by the TMA in a pulse shift modulation mode to control the periodic switching of the array elements of the uniform linear array, and the radar echo signal is generated after the radar signal is reflected by the target and received through a single channel; The compensation module is used to construct a digital down-conversion filter based on the characteristic of the TMA that can generate a fundamental component and an infinite number of harmonic components. The filter is used to extract the harmonic component A of the radar echo signal. The radar echo signal in a static environment is mixed to obtain the frequency-shifted harmonic component B. The phase slope of the harmonic component B is determined based on the frequency-shifted harmonic component B. The phase slope is used to compensate the frequency offset of the harmonic component A to obtain a stable harmonic component. The monitoring module is used to determine the phase of each harmonic component based on the stable harmonic component to obtain the user's time-domain breathing information.

10. An electronic device, characterized in that: include: memory for storing computer programs; A processor is configured to execute the computer program to implement the steps of the multi-user respiration monitoring method based on a time modulation array according to any one of claims 1 to 8.

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