A millimeter wave radar-based mobile target heartbeat frequency measurement system and method

Abstract

The application discloses a kind of mobile target heartbeat frequency measurement system and method based on millimeter wave radar, comprising: millimeter wave signal acquisition module, for obtaining intermediate frequency signal;Feature extraction module, for the distance-Fourier transform of intermediate frequency signal, obtain distance-amplitude spectrum;Mobile target positioning module, for locating the distance unit where the mobile target in scene from distance-amplitude spectrum;Target signal generation module, for extracting and generating continuous signal about mobile target from distance unit;Heartbeat signal separation module, for separating out heartbeat signal;Heartbeat frequency calculation module, for calculating heartbeat BPM and average heartbeat peak spacing IBI.The present application can locate the mobile target in space, and the spectrum of subdivided distance unit is extracted by the mode of Chirp-Z transform to replace the spectrum of distance unit in the moment when signal leakage exists to adjacent distance unit, and continuous signal about mobile target is generated.

Description

Technical Field

[0001] This invention belongs to the field of heartbeat sensing technology, specifically relating to a system and method for measuring the heartbeat frequency of a moving target based on millimeter-wave radar. Background Technology

[0002] With advancements in sensing technology and improvements in living standards, the demand for heartbeat sensing technology is increasing daily. Traditional heartbeat sensing technologies, such as electrocardiographs, offer high measurement accuracy, but due to their high deployment costs and cumbersome measurement processes, they are only suitable for specialized medical diagnostic scenarios. Therefore, there is a need to promote and popularize a heartbeat sensing technology that is low in deployment costs and easy to use, in order to meet the growing demand for health monitoring and preliminary diagnosis.

[0003] Currently, the main methods for measuring target heart rate include the following:

[0004] 1. Sensor-based methods mainly rely on the different light transmittance of the pulse in different states. The sensor converts the photoelectric signal that changes with the heartbeat into a digital signal to measure the heart rate. This method requires the user to wear and touch the measuring device with the sensor, which has the problems of inconvenience in measurement and high deployment cost.

[0005] 2. The computer vision-based method mainly captures human facial images through a camera and uses image magnification algorithms to extract minute disturbances in the flow of blood vessels in the image, thereby realizing heart rate measurement. This method is greatly affected by factors such as lighting conditions, movement status, and skin color, and requires the user to face the camera, so the measurement conditions are relatively limited.

[0006] 3. The wireless signal-based method mainly uses wireless sensing devices to detect minute displacements from the user's chest cavity and analyzes the Doppler effect or phase changes to measure heart rate. However, this method is greatly affected by minute disturbances and cannot measure the heart rate of moving targets. Summary of the Invention

[0007] To address the shortcomings of the prior art, the present invention aims to provide a moving target heartbeat frequency measurement system and method based on millimeter-wave radar, thereby solving the problem that the prior art can only measure the heartbeat of static targets and is difficult to accurately measure the heartbeat frequency of moving targets. The present invention achieves the measurement of the heartbeat frequency of moving targets through millimeter-wave wireless radio frequency signals.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] The present invention discloses a moving target heartbeat frequency measurement system based on millimeter-wave radar, comprising: a millimeter-wave signal acquisition module and a data processing module.

[0010] The millimeter-wave signal acquisition module is used to transmit linear frequency modulated millimeter-wave signals, receive linear frequency modulated millimeter-wave signals reflected by targets in the scene, mix the transmitted and received signals to obtain intermediate frequency signals, and transmit the intermediate frequency signals to the data processing module.

[0011] The data processing module includes: a feature extraction module, a moving target localization module, a target signal generation module, a heartbeat signal separation module, and a heartbeat frequency calculation module;

[0012] The feature extraction module is used to perform distance-Fourier transform on the intermediate frequency signal to obtain the distance-amplitude spectrum, so as to distinguish the intermediate frequency signals from different distance units in the scene with coarse granularity;

[0013] The moving target localization module is used to locate the range cell of a moving target in a scene from the range-amplitude spectrum;

[0014] The target signal generation module is used to extract the spectrum corresponding to the distance cell from the distance cell where the moving target is located and generate a continuous signal about the moving target;

[0015] A heartbeat signal separation module is used to separate the heartbeat signal from a continuous signal about a moving target;

[0016] The heart rate calculation module is used to calculate the number of heartbeats per minute (BPM) and the average heartbeat peak interval (IBI) in the heartbeat signal.

[0017] Furthermore, the moving target refers to a person whose heart rate needs to be measured who is moving within the scene.

[0018] Furthermore, the moving target localization module specifically includes:

[0019] The CA-CFAR algorithm is used to estimate the range cell in the range-amplitude spectrum at a certain time. noise threshold The expression is as follows:

[0020] ;

[0021] In the formula, for Reference distance cell, , The total number of reference distance cells, For distance unit Energy level;

[0022] set up For a certain distance unit The energy level, i.e. the amplitude of the spectrum, is expressed by the following formula:

[0023] ;

[0024] In the formula, This indicates the intermediate frequency signal within that distance cell at that moment; For threshold factor, The calculation expression is as follows:

[0025] ;

[0026] In the formula, Let be the expected false alarm probability; if the energy level of the range cell to be measured is greater than the noise level of its corresponding reference range cell, then the following condition is met. , indicating the distance unit to be measured There may be dynamic targets at any given time; multiple range cells may contain dynamic targets at any given moment. The range cell with the highest energy level within the measurement range is selected. The distance unit, representing the location of the moving target at that moment, enables the localization of the moving target. The calculation expression is as follows:

[0027] ;

[0028] In the formula, For distance unit Energy level.

[0029] Furthermore, the dynamic target refers to other moving people who may exist in the scene.

[0030] Furthermore, the target signal generation module specifically includes:

[0031] The distance unit of the moving target obtained from the moving target localization module is determined. Adjacent distance units at the same time energy level If energy level Its noise threshold Then it is assumed that the signal corresponding to the moving target at that moment is simultaneously in the range unit. and distance unit There are components in the intermediate frequency signal at each moment. The Chirp-Z transform algorithm is used to calculate the subdivided distance-amplitude spectrum at that moment; for the intermediate frequency signal at a certain moment... ,in For the first The signal of each distance unit , If the total number of distance cells is , then the distance cells Corresponding distance-amplitude spectrum It can be calculated by the following expression:

[0032] ;

[0033] In the formula, It is the natural logarithm. The imaginary unit;

[0034] Replacing the FFT transform with the Chirp-Z transform results in subdivided distance cells. The corresponding subdivided distance-amplitude spectrum It can be calculated by the following expression:

[0035] ;

[0036] In the formula, For subdivided distance units The distribution along the spiral path in the Z-plane is expressed as follows:

[0037] ;

[0038] In the formula, As the starting distance unit, ; The ratio of sampling points. ; The radius of the spiral path of the initial distance element in the Z-plane. The initial angular frequency, The rate of change of the spiral, Let M be the angular frequency step size, and M be the total number of distance cells; take... , , , To obtain the distance unit of the moving target and adjacent distance units The subdivided distance units between The corresponding subdivided distance-amplitude spectrum For each moment when a signal leaks to an adjacent distance cell, calculate... To replace the current time distance unit The corresponding spectrum By connecting the spectrum of the target's distance cells at each moment, a continuous signal about the moving target is generated. The expression is as follows:

[0039] ;

[0040] In the formula, For a moment The spectrum of the distance cell where the target is located. , This represents the total number of intermediate frequency signals.

[0041] Furthermore, the signal leakage to adjacent distance cells refers to the fact that the target moves in the scene and is not always in the same distance cell. When the moving target is located between two adjacent distance cells, its signal will leak to the adjacent distance cells.

[0042] Furthermore, the heartbeat signal separation module specifically includes:

[0043] Using the VMD algorithm to analyze continuous signals about a moving target Decomposed into The intrinsic mode functions (IMFs) are selected, and those with center frequencies within the heartbeat frequency range are synthesized to obtain the final target heartbeat signal. ;

[0044] Set continuous signals for moving targets. Decomposed into eigenmode functions , , The corresponding center frequency is ,as follows:

[0045] ;

[0046] In the formula, The residual trend term is used; mode decomposition is achieved by optimizing the following objective function to reduce the overlap between the eigenmode functions, as follows:

[0047] ;

[0048] In the formula, For Hilbert transform operators, By introducing a quadratic penalty term and Lagrange multipliers, the objective function optimization problem can be transformed into an unconstrained optimization problem, as follows:

[0049] ;

[0050] In the formula, For bandwidth-constrained balancing parameters, Let the Lagrange multipliers be the solutions; the Alternating Direction Multiplier Method (ADMM) is used to obtain the solution to this optimization problem; let... Represents the intrinsic mode function Fast Fourier Transform In the The result of round iteration, Indicates center frequency In the The result of round iteration, Represents Lagrange multipliers Fast Fourier Transform In the The result of round iteration, , , Update using the following formulas respectively , , :

[0051] ;

[0052] ;

[0053] ;

[0054] Until the iteration round Reaching the upper limit Or the difference between two rounds of updates All less than the tolerance ,in For frequency variables, To update the step size of the Lagrange multipliers, =1,2,…,K; for intrinsic mode functions Fast Fourier Transform The final iterative result Using the inverse Fourier transform, the real part is the eigenmode function. Its center frequency corresponds to the converged frequency obtained The target heartbeat signal is obtained by synthesizing the intrinsic mode functions with center frequencies within the heartbeat frequency range using amplitude as weight. The calculation formula is as follows:

[0055] ;

[0056] In the formula, This represents the range of heart rate values. for The weight can be calculated using the following formula:

[0057] ;

[0058] In the formula, express The length.

[0059] Furthermore, the heart rate calculation module specifically includes:

[0060] Statistical target heartbeat signal The peak point in time, and excluded from time. The memory detects the target heartbeat signal at other peak points. The point set of R peaks in ,in It is the reciprocal of the highest human heart rate; heart rate is measured using heart rate in beats per minute (BPM) and mean heart rate interval (IBI) as standards. The formula for calculating heart rate in BPM is as follows:

[0061] ;

[0062] In the formula, To measure the total duration;

[0063] The formula for calculating the mean heart rate interval (IBI) is as follows:

[0064] ;

[0065] In the formula, Indicates the first The time corresponding to each peak Indicates the first The time corresponding to each peak .

[0066] This invention also provides a method for measuring the heartbeat frequency of a moving target based on millimeter-wave radar. Based on the above system, the steps are as follows:

[0067] 1) Transmit a linear frequency modulated millimeter wave signal, receive the linear frequency modulated millimeter wave signal reflected by the target in the scene, and mix the transmitted and received signals to obtain an intermediate frequency signal;

[0068] 2) Perform a distance-Fourier transform on the intermediate frequency signal to obtain the distance-amplitude spectrum;

[0069] 3) Locate the range cells where a moving target may exist, and determine the range cell where the moving target is located based on the energy level in the range cell;

[0070] 4) Perform Chirp-Z transform on the intermediate frequency signal corresponding to the moment when there is also a moving target in the adjacent cell of the distance cell where the moving target is located, to obtain the distance cell subdivided at that moment, extract its spectrum to replace the spectrum of the distance cell with respect to the moving target obtained in step 3), and connect the spectrum of the distance cell with respect to the moving target at all moments to generate a continuous signal with respect to the moving target.

[0071] 5) The VMD algorithm is used to extract the intrinsic mode functions with center frequencies within the heartbeat frequency range from the continuous signal about the moving target, and then weighted and synthesized to obtain the target heartbeat signal;

[0072] 6) Calculate the target heartbeat signal's heartbeats per minute (BPM) and average heartbeat interval (IBI).

[0073] The beneficial effects of this invention are:

[0074] This invention can locate moving targets in space. It extracts the spectrum of subdivided range cells using Chirp-Z transform to replace the spectrum of range cells at times when there is signal leakage to adjacent range cells. It then connects the spectra of range cells with respect to the moving target at all times to generate a continuous signal with respect to the moving target.

[0075] This invention can obtain the target's heartbeat signal from continuous signals about the moving target, and can realize the measurement of the heartbeat frequency of the moving target without wearing a device, which is beneficial to downstream tasks such as telemedicine and health monitoring.

[0076] This invention employs non-contact, non-intrusive sensing technology, which can promptly sense and measure the heart rate of moving targets in a scene without requiring the cooperation of other machines.

[0077] This invention uses millimeter-wave radar for sensing, which is convenient to deploy in any location and is inexpensive, and can work normally in complex environments. Attached Figure Description

[0078] Figure 1 This is a schematic diagram of the system of the present invention.

[0079] Figure 2 This is a schematic diagram illustrating the principle of millimeter-wave signal acquisition in this invention.

[0080] Figure 3 This is a schematic diagram of the data processing module in this invention. Detailed Implementation

[0081] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to embodiments and accompanying drawings. The content mentioned in the embodiments is not intended to limit the present invention.

[0082] Reference Figures 1 to 3 As shown, the present invention provides a moving target heartbeat frequency measurement system based on millimeter-wave radar, comprising: a millimeter-wave signal acquisition module and a data processing module.

[0083] The millimeter-wave signal acquisition module is used to transmit linear frequency modulated millimeter-wave signals, receive linear frequency modulated millimeter-wave signals reflected by targets in the scene, mix the transmitted and received signals to obtain intermediate frequency signals, and transmit the intermediate frequency signals to the data processing module.

[0084] The data processing module includes: a feature extraction module, a moving target localization module, a target signal generation module, a heartbeat signal separation module, and a heartbeat frequency calculation module;

[0085] The feature extraction module is used to perform distance-Fourier transform on the intermediate frequency signal to obtain the distance-amplitude spectrum, so as to distinguish the intermediate frequency signals from different distance units in the scene with coarse granularity;

[0086] The moving target localization module is used to locate the range cell of a moving target in a scene from the range-amplitude spectrum;

[0087] The moving target refers to a person whose heart rate needs to be measured while moving within the scene.

[0088] In the example, the moving target localization module specifically includes:

[0089] The CA-CFAR algorithm is used to estimate the range cell in the range-amplitude spectrum at a certain time. noise threshold The expression is as follows:

[0090] ;

[0091] In the formula, for Reference distance cell, , The total number of reference distance cells, For distance unit Energy level;

[0092] set up For a certain distance unit The energy level, i.e. the amplitude of the spectrum, is expressed by the following formula:

[0093] ;

[0094] In the formula, This indicates the intermediate frequency signal within that distance cell at that moment; For threshold factor, The calculation expression is as follows:

[0095] ;

[0096] In the formula, Let be the expected false alarm probability; if the energy level of the range cell to be measured is greater than the noise level of its corresponding reference range cell, then the following condition is met. , indicating the distance unit to be measured There may be dynamic targets at any given time; multiple range cells may contain dynamic targets at any given moment. The range cell with the highest energy level within the measurement range is selected. The distance unit, representing the location of the moving target at that moment, enables the localization of the moving target. The calculation expression is as follows:

[0097] ;

[0098] In the formula, For distance unit Energy level.

[0099] The dynamic target refers to other moving people that may exist in the scene.

[0100] The target signal generation module is used to extract the spectrum corresponding to the distance cell from the distance cell where the moving target is located and generate a continuous signal about the moving target;

[0101] In the example, the target signal generation module specifically includes:

[0102] The distance unit of the moving target obtained from the moving target localization module is determined. Adjacent distance units at the same time energy level If energy level Its noise threshold Then it is assumed that the signal corresponding to the moving target at that moment is simultaneously in the range unit. and distance unit There are components in the intermediate frequency signal at each moment. The Chirp-Z transform algorithm is used to calculate the subdivided distance-amplitude spectrum at that moment; for the intermediate frequency signal at a certain moment... ,in For the first The signal of each distance unit , If the total number of distance cells is , then the distance cells Corresponding distance-amplitude spectrum It can be calculated by the following expression:

[0103] ;

[0104] In the formula, It is the natural logarithm. The imaginary unit;

[0105] Replacing the FFT transform with the Chirp-Z transform results in subdivided distance cells. The corresponding subdivided distance-amplitude spectrum It can be calculated by the following expression:

[0106] ;

[0107] In the formula, For subdivided distance units The distribution along the spiral path in the Z-plane is expressed as follows:

[0108] ;

[0109] In the formula, As the starting distance unit, ; The ratio of sampling points. ; The radius of the spiral path of the initial distance element in the Z-plane. The initial angular frequency, The rate of change of the spiral, Let M be the angular frequency step size, and M be the total number of distance cells; take... , , , To obtain the distance unit of the moving target and adjacent distance units The subdivided distance units between The corresponding subdivided distance-amplitude spectrum For each moment when a signal leaks to an adjacent distance cell, calculate... To replace the current time distance unit The corresponding spectrum By connecting the spectrum of the distance cells to the target at each moment, a continuous signal about the moving target is generated. The expression is as follows:

[0110] ;

[0111] In the formula, For a moment The spectrum of the distance cell where the target is located. , This represents the total number of intermediate frequency signals.

[0112] The signal leakage to adjacent distance cells refers to the fact that when a target moves in the scene, it is not always in the same distance cell. When a moving target is located between two adjacent distance cells, its signal will leak to the adjacent distance cells.

[0113] A heartbeat signal separation module is used to separate the heartbeat signal from a continuous signal about a moving target;

[0114] In the example, the heartbeat signal separation module specifically includes:

[0115] Using the VMD algorithm to analyze continuous signals about a moving target Decomposed into The intrinsic mode functions (IMFs) are selected, and those with center frequencies within the heartbeat frequency range are synthesized to obtain the final target heartbeat signal. ;

[0116] Set continuous signals for the moving target. Decomposed into Individual eigenmode functions , , The corresponding center frequency is ,as follows:

[0117] ;

[0118] In the formula, The residual trend term is used; mode decomposition is achieved by optimizing the following objective function to reduce the overlap between the eigenmode functions, as follows:

[0119] ;

[0120] In the formula, For Hilbert transform operators, By introducing a quadratic penalty term and Lagrange multipliers, the objective function optimization problem can be transformed into an unconstrained optimization problem, as follows:

[0121] ;

[0122] In the formula, For bandwidth-constrained balancing parameters, Let the Lagrange multipliers be the solutions; the Alternating Direction Multiplier Method (ADMM) is used to obtain the solution to this optimization problem; let... Represents the intrinsic mode function Fast Fourier Transform In the The result of round iteration, Indicates center frequency In the The result of round iteration, Represents Lagrange multipliers Fast Fourier Transform In the The result of round iteration, , , Update using the following formulas respectively , , :

[0123] ;

[0124] ;

[0125] ;

[0126] Until the iteration round Reaching the upper limit Or the difference between two rounds of updates All less than the tolerance ,in For frequency variables, To update the step size of the Lagrange multipliers, =1,2,…,K; for intrinsic mode functions Fast Fourier Transform The final iterative result Using the inverse Fourier transform, the real part is the eigenmode function. Its center frequency corresponds to the converged frequency obtained The target heartbeat signal is obtained by synthesizing the intrinsic mode functions with center frequencies within the heartbeat frequency range using amplitude as weight. The calculation formula is as follows:

[0127] ;

[0128] In the formula, This represents the range of heart rate values. for The weight can be calculated using the following formula:

[0129] ;;

[0130] In the formula, express The length.

[0131] The heart rate calculation module is used to calculate the number of heartbeats per minute (BPM) and the average heartbeat peak interval (IBI) in the heartbeat signal;

[0132] In the example, the heart rate calculation module specifically includes:

[0133] Statistical target heartbeat signal The peak point in time, and excluded from time. The memory detects the target heartbeat signal at other peak points. The point set of R peaks in ,in It is the reciprocal of the highest human heart rate; heart rate is measured using heart rate in beats per minute (BPM) and mean heart rate interval (IBI) as standards. The formula for calculating heart rate in BPM is as follows:

[0134] ;

[0135] In the formula, To measure the total duration;

[0136] The formula for calculating the mean heart rate interval (IBI) is as follows:

[0137] ;

[0138] In the formula, Indicates the first The time corresponding to each peak Indicates the first The time corresponding to each peak .

[0139] Furthermore, this invention also provides a method for measuring the heartbeat frequency of a moving target based on millimeter-wave radar. Based on the above system, the steps are as follows:

[0140] 1) Transmit a linear frequency modulated millimeter wave signal, receive the linear frequency modulated millimeter wave signal reflected by the target in the scene, and mix the transmitted and received signals to obtain an intermediate frequency signal;

[0141] 2) Perform a distance-Fourier transform on the intermediate frequency signal to obtain the distance-amplitude spectrum;

[0142] 3) Locate the range cells where a moving target may exist, and determine the range cell where the moving target is located based on the energy level in the range cell;

[0143] 4) Perform Chirp-Z transform on the intermediate frequency signal corresponding to the moment when there is also a moving target in the adjacent cell of the distance cell where the moving target is located, to obtain the distance cell subdivided at that moment, extract its spectrum to replace the spectrum of the distance cell with respect to the moving target obtained in step 3), and connect the spectrum of the distance cell with respect to the moving target at all moments to generate a continuous signal with respect to the moving target.

[0144] 5) The VMD algorithm is used to extract the intrinsic mode functions with center frequencies within the heartbeat frequency range from the continuous signal about the moving target, and then weighted and synthesized to obtain the target heartbeat signal;

[0145] 6) Calculate the target heartbeat signal's heartbeats per minute (BPM) and average heartbeat interval (IBI).

[0146] This invention has many specific applications. The above description is only a preferred embodiment of this invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention.

Claims

1. A moving target heartbeat frequency measurement system based on millimeter-wave radar, characterized in that, include: Millimeter-wave signal acquisition module and data processing module: The millimeter-wave signal acquisition module is used to transmit linear frequency modulated millimeter-wave signals, receive linear frequency modulated millimeter-wave signals reflected by targets in the scene, mix the transmitted and received signals to obtain intermediate frequency signals, and transmit the intermediate frequency signals to the data processing module. The data processing module includes: a feature extraction module, a moving target localization module, a target signal generation module, a heartbeat signal separation module, and a heartbeat frequency calculation module; The feature extraction module is used to perform distance-Fourier transform on the intermediate frequency signal to obtain the distance-amplitude spectrum, so as to distinguish the intermediate frequency signals from different distance units in the scene with coarse granularity; The moving target localization module is used to locate the range cell of a moving target in a scene from the range-amplitude spectrum; The target signal generation module is used to extract the spectrum corresponding to the distance cell from the distance cell where the moving target is located and generate a continuous signal about the moving target; A heartbeat signal separation module is used to separate the heartbeat signal from a continuous signal about a moving target; The heart rate calculation module is used to calculate the number of heartbeats per minute (BPM) and the average heartbeat peak interval (IBI) in the heartbeat signal.

2. The moving target heartbeat frequency measurement system based on millimeter-wave radar according to claim 1, characterized in that, The moving target refers to a person whose heart rate needs to be measured while moving within the scene.

3. The moving target heartbeat frequency measurement system based on millimeter-wave radar according to claim 1, characterized in that, The moving target localization module specifically includes: The CA-CFAR algorithm is used to estimate the range cell in the range-amplitude spectrum at a certain time. noise threshold The expression is as follows: ； In the formula, for Reference distance cell, , The total number of reference distance cells, For distance unit Energy level; set up For a certain distance unit The energy level, i.e. the amplitude of the spectrum, is expressed by the following formula: ； In the formula, This indicates the intermediate frequency signal within that distance cell at that moment; For threshold factor, The calculation expression is as follows: ； In the formula, Let be the expected false alarm probability; if the energy level of the range cell to be measured is greater than the noise level of its corresponding reference range cell, then the following condition is met. , indicating the distance unit to be measured There may be dynamic targets at any given time; multiple range cells may contain dynamic targets at any given moment. The range cell with the highest energy level within the measurement range is selected. The distance unit, representing the location of the moving target at that moment, enables the localization of the moving target. The calculation expression is as follows: ； In the formula, For distance unit Energy level.

4. The moving target heartbeat frequency measurement system based on millimeter-wave radar according to claim 3, characterized in that, The target signal generation module specifically includes: The distance unit of the moving target obtained from the moving target localization module is determined. Adjacent distance units at the same time energy level If energy level Its noise threshold Then it is assumed that the signal corresponding to the moving target at that moment is simultaneously in the range unit. and distance unit There are components in all frequencies, and the Chirp-Z transform algorithm is used to calculate the subdivided distance-amplitude spectrum at that moment; for the intermediate frequency signal at a certain moment... ,in For the first The signal of each distance unit , If the total number of distance cells is , then the distance cells Corresponding distance-amplitude spectrum It can be calculated by the following expression: ； In the formula, It is the natural logarithm. The imaginary unit; Replacing the FFT transform with the Chirp-Z transform results in subdivided distance cells. The corresponding subdivided distance-amplitude spectrum It can be calculated by the following expression: ； In the formula, For subdivided distance units The distribution along the spiral path in the Z-plane is expressed as follows: ； In the formula, As the starting distance unit, ; The ratio of sampling points. ; The radius of the spiral path of the initial distance element in the Z-plane. The initial angular frequency, The rate of change of the spiral, Let M be the angular frequency step size, and M be the total number of distance cells; take... , , , To obtain the distance unit of the moving target and adjacent distance units The subdivided distance units between The corresponding subdivided distance-amplitude spectrum For each moment when a signal leaks to an adjacent distance cell, calculate... To replace the current time distance unit The corresponding spectrum By connecting the spectrum of the distance cells to the target at each moment, a continuous signal about the moving target is generated. The expression is as follows: ； In the formula, For a moment The spectrum of the distance cell where the target is located. , This represents the total number of intermediate frequency signals.

5. The moving target heartbeat frequency measurement system based on millimeter-wave radar according to claim 4, characterized in that, The heartbeat signal separation module specifically includes: Using the VMD algorithm to analyze continuous signals about a moving target Decomposed into The intrinsic mode functions (IMFs) are selected, and those with center frequencies within the heartbeat frequency range are synthesized to obtain the final target heartbeat signal. ; Set continuous signals for the moving target. Decomposed into Individual eigenmode functions , , The corresponding center frequency is ,as follows: ； In the formula, The residual trend term is used; mode decomposition is achieved by optimizing the following objective function to reduce the overlap between the eigenmode functions, as follows: ； In the formula, For Hilbert transform operators, By introducing a quadratic penalty term and Lagrange multipliers, the objective function optimization problem can be transformed into an unconstrained optimization problem, as follows: ； In the formula, For bandwidth-constrained balancing parameters, Let the Lagrange multipliers be the solutions; the Alternating Direction Multiplier Method (ADMM) is used to obtain the solution to this optimization problem; let... Represents the intrinsic mode function Fast Fourier Transform In the The result of round iteration, Indicates center frequency In the The result of round iteration, Represents Lagrange multipliers Fast Fourier Transform In the The result of round iteration, , , Update using the following formulas respectively , , : ； ； ； Until the iteration round Reaching the upper limit Or the difference between two rounds of updates All less than the tolerance ,in For frequency variables, To update the step size of the Lagrange multipliers, =1,2,…,K; for intrinsic mode functions Fast Fourier Transform The final iterative result Using the inverse Fourier transform, the real part is the eigenmode function. Its center frequency corresponds to the converged frequency obtained The target heartbeat signal is obtained by synthesizing the intrinsic mode functions with center frequencies within the heartbeat frequency range using amplitude as weight. The calculation formula is as follows: ； In the formula, This represents the range of heart rate values. for The weight is calculated using the following formula: ； In the formula, express The length.

6. The moving target heartbeat frequency measurement system based on millimeter-wave radar according to claim 5, characterized in that, The heart rate calculation module specifically includes: Statistical target heartbeat signal The peak point in time, and excluded from time. The memory detects the target heartbeat signal at other peak points. The point set of R peaks in ,in It is the reciprocal of the highest human heart rate; heart rate is measured using heart rate in beats per minute (BPM) and mean heart rate interval (IBI) as standards. The formula for calculating heart rate in BPM is as follows: ； In the formula, To measure the total duration; The formula for calculating the mean heart rate interval (IBI) is as follows: ； In the formula, Indicates the first The time corresponding to each peak Indicates the first The time corresponding to each peak .

7. The moving target heartbeat frequency measurement system based on millimeter-wave radar according to claim 1, characterized in that, The dynamic target refers to other moving people that may exist in the scene.

8. A method for measuring the heart rate of a moving target based on millimeter-wave radar, based on the system described in any one of claims 1-7, characterized in that, The steps are as follows: 1) Transmit a linear frequency modulated millimeter wave signal, receive the linear frequency modulated millimeter wave signal reflected by the target in the scene, and mix the transmitted and received signals to obtain an intermediate frequency signal; 2) Perform a distance-Fourier transform on the intermediate frequency signal to obtain the distance-amplitude spectrum; 3) Locate the range cells where a moving target may exist, and determine the range cell where the moving target is located based on the energy level in the range cell; 4) Perform Chirp-Z transform on the intermediate frequency signal corresponding to the moment when there is also a moving target in the adjacent cell of the distance cell where the moving target is located, to obtain the distance cell subdivided at that moment, extract its spectrum to replace the spectrum of the distance cell with respect to the moving target obtained in step 3), and connect the spectrum of the distance cell with respect to the moving target at all moments to generate a continuous signal with respect to the moving target. 5) The VMD algorithm is used to extract the intrinsic mode functions with center frequencies within the heartbeat frequency range from the continuous signal about the moving target, and then weighted and synthesized to obtain the target heartbeat signal; 6) Calculate the target heartbeat signal's heartbeats per minute (BPM) and average heartbeat interval (IBI).

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