Non-contact vital sign detection system and method

Abstract

The invention discloses a non-contact vital sign detection system and method. The system comprises a pair of orthogonally arranged microstrip leaky-wave antennas used for transmitting and receiving horizontal polarization and vertical polarization signals; the millimeter wave signal transmitting module is used for generating a linear frequency modulation continuous wave signal, controlling the microstrip leaky-wave antenna to perform frequency scanning in a set frequency range, and realizing three-dimensional space energy distribution imaging; the signal processing module is used for carrying out distance-azimuth-pitching joint inversion on the echo signals in a target locking stage, generating a three-dimensional energy diagram and identifying and locking space coordinates, postures and parts of a plurality of targets; and the monitoring module is used for extracting the vital sign information of the target through small-bandwidth frequency sweeping or phase disturbance measurement near the fixed center frequency in a sign monitoring stage after the target is locked. According to the invention, the inherent contradiction between scanning and precision measurement of the leaky-wave antenna is solved through the two-stage working mode and the division and cooperation of the double antennas in the azimuth angle dimension and the pitch angle dimension.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of millimeter wave radar, in particular to a non-contact vital sign detection system and method based on double vertical leaky wave antennas. BACKGROUND

[0002] In recent years, non-contact vital sign detection (such as respiration, heartbeat) technology has shown broad application prospects in medical monitoring, smart home, security monitoring and other fields. Millimeter wave radar has become a research hotspot in this field because it can penetrate clothing and detect small chest fluctuations and pulse vibrations.

[0003] Existing millimeter wave radar solutions mainly fall into two categories: one is mechanical scanning radar, which is large in size, has wear and tear, and has slow scanning speed; the other is phased array radar, which has flexible and fast beam control, but requires complex feed networks and expensive phase shifter components, resulting in high system cost and power consumption.

[0004] Microstrip leaky wave antenna (mLWA) as an alternative antenna solution, its beam pointing changes with operating frequency, and no phase shifter is needed to achieve electronic scanning, with the advantages of simple structure, low cost and easy integration. However, the application of leaky wave antennas in vital sign detection faces a fundamental contradiction: in order to scan and locate the target, the antenna needs to constantly change the frequency (and thus the beam pointing); but in order to detect weak vital sign signals with high precision, the beam needs to stably and continuously irradiate the same target point for coherent phase detection. This inherent conflict between scanning and measurement makes it difficult for traditional leaky wave antenna systems to achieve reliable vital sign monitoring.

[0005] It should be particularly noted that existing single leaky wave antenna or same-direction double leaky wave antenna solutions lack independent beam control capability in two orthogonal dimensions, and cannot achieve accurate three-dimensional spatial positioning to form a three-dimensional echo energy map, thus cannot solve the above-mentioned scanning and measurement contradiction.

[0006] Therefore, there is an urgent need for a new system architecture that can retain the low-cost, simple structure advantages of microstrip leaky wave antennas, while overcoming the scanning-measurement contradiction. SUMMARY

[0007] The main purpose of the present application is to propose a non-contact vital sign detection system and method based on double vertical leaky wave antennas, aiming to solve the inherent contradiction between scanning and precise measurement of leaky wave antennas through a unique two-stage working mode and the division and cooperation of double antennas in azimuth and elevation dimensions.

[0008] To achieve the above object, the application provides a non-contact vital sign detection system, comprising: A pair of orthogonally arranged microstrip leaky-wave antennas: used for transmitting and receiving horizontal polarization and vertical polarization signals respectively; A millimeter wave signal transmitting module: connected with the microstrip leaky-wave antennas, used for generating a linear frequency modulation continuous wave signal and controlling the microstrip leaky-wave antennas to perform frequency scanning in a set frequency range to form a virtual array and realize three-dimensional space energy distribution imaging; A signal processing module: used for performing distance-azimuth-elevation joint inversion on echo signals in a target locking stage to generate a three-dimensional energy graph and identify the spatial three-dimensional coordinates, posture and part of multiple locked targets; A monitoring module: used for extracting target vital sign information by small bandwidth frequency scanning or phase disturbance measurement around a fixed center frequency in a sign monitoring stage after the target is locked; A control module: used for coordinating the switching of the target locking stage and the sign monitoring stage, completing timing control and data fusion.

[0009] The further technical scheme of the application is that the pair of orthogonally arranged microstrip leaky-wave antennas comprises: A horizontal polarization leaky-wave antenna, whose beam pointing direction changes with frequency and scans in the azimuth angle dimension; A vertical polarization leaky-wave antenna, whose beam pointing direction changes with frequency and scans in the elevation angle dimension.

[0010] The further technical scheme of the application is that the signal processing module comprises a three-dimensional inversion unit and a feature recognition unit, wherein, The three-dimensional inversion unit is used for performing phase recovery and energy reconstruction on echo signals by using a distance-azimuth-elevation joint inversion algorithm; The feature recognition unit is used for extracting features of a generated three-dimensional energy graph by using a deep learning or template matching method, and used for identifying the spatial distribution and posture features of multiple targets.

[0011] The further technical scheme of the application is that the monitoring module is also used for detecting phase changes caused by slight movements by using a phase disturbance micro-displacement measurement method, and extracting a breathing frequency and a heartbeat frequency by using a fast Fourier transform and a band-pass filtering algorithm to realize non-contact vital sign monitoring.

[0012] The further technical scheme of the application is that the control module is also used for realizing system mode switching and resource scheduling based on a reinforcement learning algorithm, dynamically optimizing a frequency scanning range and a sampling rate by monitoring signal strength, noise level and energy consumption state in real time to realize adaptive balance of energy consumption and calculation delay.

[0013] The further technical scheme of the present application is that the system further comprises a data fusion and visualization module, which is used for fusing and displaying three-dimensional space perception results and vital sign data, generating a visual monitoring interface, and performing multi-target state tracking and historical data tracing.

[0014] To achieve the above-mentioned purpose, the present application further provides a non-contact vital sign detection method, which is applied to the non-contact vital sign detection system as described above, and comprises the following steps: Step S10, in the target locking stage, the horizontal polarization leaky wave antenna and the vertical polarization leaky wave antenna are controlled to perform cooperative frequency scanning in respective dimensions, so as to perform omnidirectional two-dimensional detection on the monitoring area; Step S20, the echo signal is processed, and the three-dimensional coordinates of at least one to-be-detected target in space are calculated by using a direction of arrival estimation algorithm, wherein the three-dimensional coordinates comprise azimuth angle, elevation angle and distance information; Step S30, in the vital sign monitoring stage, the corresponding working frequencies required for locking of the horizontal polarization leaky wave antenna and the vertical polarization leaky wave antenna are calculated according to the three-dimensional coordinates of the to-be-detected target in space determined in the target locking stage; Step S40, the horizontal polarization leaky wave antenna is controlled to stop scanning, and the working frequency thereof is fixed to the frequency corresponding to the azimuth angle; Step S50, the vertical polarization leaky wave antenna is controlled to stop scanning, and the working frequency thereof is fixed to the frequency corresponding to the elevation angle; Step S60, the beams of the horizontal polarization leaky wave antenna and the vertical polarization leaky wave antenna are made to intersect in space, and jointly and continuously irradiate the locked target point; Step S70, in the stable irradiation state, the phase information of the echo is collected and analyzed, and the vital sign features of the target are extracted by using a phase demodulation algorithm, wherein the vital sign features comprise respiratory and heartbeat waveforms.

[0015] The further technical scheme of the present application is that the three-dimensional coordinate estimation in step S20 is performed by using a two-dimensional MUSIC algorithm combined with distance FFT; The step S20 comprises: Step S201, constructing a signal model: scanning at N frequency points, and modeling the received signal as: x =α·a(θ,ϕ)+n (1) Wherein: x is a received signal vector; α is a complex amplitude, which comprises a target reflection coefficient and a phase term e −j4πR / λ ; a(θ, ϕ) is an array steering vector, and the elements thereof represent the phase delay of electromagnetic waves arriving at each virtual array element from the direction (θ, ϕ); n is an additive noise vector; and λ is a wavelength; Step S202, covariance matrix calculation and decomposition: calculate the covariance matrix R of the received data xx = E[xx H ], and perform eigenvalue decomposition, and divide the eigenvectors into signal subspace U s and noise subspace U n ; Step S203, spatial spectrum estimation and peak search: construct a two-dimensional MUSIC spatial spectrum function: P MUSIC (θ, ϕ) = 1 / aH(θ, ϕ)UnUHna(θ, ϕ) (2) Based on the orthogonal scanning characteristics of the horizontal and vertical antennas, by performing two-dimensional search in the azimuth and elevation angle dimensions, the peak position of the spectrum function P MUSIC is the estimated angle (θ peak , ϕ peak ) of the target; Step S204, distance estimation: perform fast Fourier transform on the echo signal, detect the position of the distance FFT spectrum peak, and calculate the accurate distance R of the target according to R = (c·∆t) / 2, wherein ∆t is the time delay; c is the speed of light.

[0016] The further technical scheme of the present application is that the step of collecting and analyzing the phase information of the echo in step S70 comprises: Step S701, analyze the phase-displacement relationship: The baseband complex signal of the radar echo can be expressed as S(t) = I(t) + jQ(t) = Ae jϕ(t) ; wherein I(t) is the real part, and Q(t) is the imaginary part.

[0017] The total phase is ϕ(t) = ϕ0+∆ϕ(t), ϕ0= 4πR0 / λ is the initial phase, and ∆ϕ(t) is the time-varying phase caused by the chest displacement x(t), which satisfies the relationship: ∆ϕ(t) = (4π / λ) x(t) (3) Step S702, extract the phase: Calculate the instantaneous phase: ϕ(t) = arctan2(Q(t), I(t)); Phase unwrapping is performed on ϕ(t) to obtain continuous phase change ϕ unwrapped (t); Subtract the initial phase to obtain the phase caused by pure displacement: ∆ϕ(t) = ϕunwrapped(t)− ϕ0; Convert into displacement signal: x(t) = (λ / 4π)·△φ(t), which x(t) is the original chest micro-motion signal containing breathing and heartbeat components; The step of extracting the target sign feature in the step S70 by the phase demodulation algorithm comprises: Step S703, preprocessing: band-pass filtering the displacement signal x(t) to remove direct current and high-frequency noise Step S704, breathing signal extraction: using a low-pass filter to directly extract a low-frequency and large-amplitude breathing signal x r (t) from the displacement signal x(t). Step S705, heartbeat signal extraction: taking the preprocessed displacement signal x(t) as the main input, which contains a strong breathing signal x r (t) and a weak heartbeat signal x h (t). Taking the extracted breathing signal x r (t) as the reference input, a least mean square adaptive filter is used to predict the breathing component in the main input with the reference input x r (t). Subtracting the filter output from the main input, an error signal e(t) = x(t)-y(t) is obtained, which is the purified heartbeat signal x h (t).

[0018] The further technical solution of the present application is that the step S705 further comprises: Step S706, fine band-pass filtering the heartbeat signal x h (t). Step S707, performing spectrum analysis or peak detection on the breathing signal x r (t) and the heartbeat signal x h (t) respectively to calculate the breathing rate and the heart rate.

[0019] The non-contact vital sign detection system and method of the present application has the following advantages: 1. The contradiction between scanning and measurement is fundamentally solved: through the two-stage mode of "scanning first and then measuring", the two conflicting tasks are separated in time, so that the system can obtain very high phase stability in the vital sign monitoring stage, which is the key to detecting weak vital signs.

[0020] 2. Realize two-dimensional scanning and three-dimensional positioning at low cost: by using horizontally and vertically orthogonal leaky-wave antennas, the system realizes two-dimensional electronic scanning and three-dimensional spatial positioning capability with the simplest hardware structure, avoiding the use of complex and expensive two-dimensional phased arrays, while ensuring the system performance while reducing the cost to the extreme.

[0021] 3. High system reliability: no mechanical moving parts, long service life; beam control is achieved through pure electronic means, switching is fast and reliable.

[0022] 4. Energy concentration, high signal-to-noise ratio: in the monitoring phase, the two beams intersect at the target point, all the energy is continuously focused on the target point, and a signal-to-noise ratio comparable to high-end radar is obtained.

[0023] 5. Flexibility and intelligence: when the target moves beyond the current beam range, the system can automatically switch back to the first stage from the second stage, re-lock the target, and has adaptive tracking capability. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the drawings shown.

[0025] Figure 1 is a flowchart of a preferred embodiment of the non-contact vital sign detection method of the present application.

[0026] The implementation of the purpose of the present application, functional characteristics and advantages will be further described with reference to the drawings. DETAILED DESCRIPTION

[0027] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0028] The present application proposes a non-contact vital sign detection system based on double vertical leaky-wave antenna, which relates to a dual-polarized leaky-wave radar system based on near-field virtual multiple-input multiple-output (NF-MIMO), which solves the inherent contradiction between scanning and precise measurement of leaky-wave antenna through two-stage working mode and the division and cooperation of double antenna in azimuth and elevation.

[0029] The working process of the non-contact vital sign detection system based on the double vertical leaky-wave antenna includes a target locking stage and a vital sign monitoring stage. The calculation scheme adopted by the non-contact vital sign detection system based on the double vertical leaky-wave antenna mainly comprises the following steps: (1) in the target locking stage, a horizontal polarization antenna and a vertical polarization antenna respectively emit a frequency-modulated continuous wave (FMCW) signal, a virtual array is formed in space through frequency scanning, near-field NF-MIMO three-dimensional imaging is realized, and a three-dimensional echo energy distribution map is generated; (2) the system performs spatial feature extraction and target identification on the three-dimensional energy map based on a range-azimuth-elevation joint inversion algorithm, and determines the positions, postures and key parts (such as the chest cavity and the neck) of multiple targets; and (3) after the target is locked, the system switches to the vital sign monitoring stage, small-bandwidth scanning or phase disturbance measurement is performed around a fixed center frequency, and non-contact high-precision detection of target vital signs (such as respiration and heartbeat) is realized.

[0030] The non-contact vital sign detection system based on the double vertical leaky-wave antenna can realize a multi-view virtual array through frequency scanning and polarization multiplexing, and can obtain three-dimensional near-field sensing capability without multi-channel receiving hardware, so that the system complexity and cost are significantly reduced.

[0031] Specifically, the preferred embodiment of the non-contact vital sign detection system based on the double vertical leaky-wave antenna comprises a pair of orthogonally arranged microstrip leaky-wave antennas, a millimeter wave signal transmitting module, a signal processing module, a monitoring module and a control module.

[0032] The pair of orthogonally arranged microstrip leaky-wave antennas are respectively used for transmitting and receiving horizontal polarization and vertical polarization signals.

[0033] The millimeter wave signal transmitting module is connected with the microstrip leaky-wave antennas, and is used for generating a frequency-modulated continuous wave signal and controlling the microstrip leaky-wave antennas to perform frequency scanning in a set frequency range, so as to form a virtual array and realize three-dimensional spatial energy distribution imaging.

[0034] The signal processing module is used for performing range-azimuth-elevation joint inversion on echo signals in the target locking stage, generating a three-dimensional energy map, and identifying the spatial three-dimensional coordinates, postures and key parts (such as the chest cavity and the neck) of multiple locked targets.

[0035] The monitoring module is used for extracting target vital sign information through small-bandwidth scanning or phase disturbance measurement around a fixed center frequency in the vital sign monitoring stage. In the monitoring stage of the embodiment, double beams intersect at a target point in space, all energy is continuously focused on the target point, and a signal-to-noise ratio comparable to high-end radar is obtained. In the vital sign monitoring stage, the extraction of all vital signs is based on stable phase information at a fixed frequency.

[0036] A control module is configured to coordinate the switching between the target locking stage and the vital sign monitoring stage, complete timing control and data fusion.

[0037] In the embodiment, the pair of orthogonally arranged microstrip leaky-wave antennas includes a horizontally polarized leaky-wave antenna and a vertically polarized leaky-wave antenna.

[0038] The horizontally polarized leaky-wave antenna has a beam pointing direction that changes with frequency and scans in the azimuth angle dimension, and the vertically polarized leaky-wave antenna has a beam pointing direction that changes with frequency and scans in the elevation angle dimension.

[0039] In the embodiment, the working mechanism of the horizontally polarized leaky-wave antenna and the vertically polarized leaky-wave antenna arranged orthogonally is as follows: The application adopts horizontally and vertically orthogonally arranged double leaky-wave antennas, which is the basis and core of realizing the system function. The horizontally arranged antenna has a beam pointing direction that changes with frequency and mainly scans in the azimuth angle dimension, and the vertically arranged antenna has a beam pointing direction that changes with frequency and mainly scans in the elevation angle dimension. The horizontally arranged antenna and the vertically arranged antenna realize the "cross locking" of the beam in space through frequency control.

[0040] The horizontally and vertically orthogonally arranged double leaky-wave antennas have the following advantages: 1. Realize complete two-dimensional scanning: in the target locking stage, the horizontally polarized leaky-wave antenna is responsible for azimuth angle scanning, and the vertically polarized leaky-wave antenna is responsible for elevation angle scanning, and the two work together to be equivalent to a simple two-dimensional electronic scanning array, so that the complete angle information (azimuth angle θ and elevation angle ϕ) of the target in space can be quickly detected and located.

[0041] 2. Realize accurate spatial intersection locking: in the vital sign monitoring stage, the two antennas are fixed at specific frequencies at which the beam pointing directions of the target θ and ϕ are fixed, and the beams produce spatial intersection at the target point (such as the human chest), forming a stable irradiation area. This design ensures that all energy is continuously focused on the target point in the monitoring stage, greatly improving the signal-to-noise ratio and phase stability.

[0042] 3. Solve the problem of missing dimension of the same direction antenna: if the two antennas are in the same direction (such as both horizontally or both vertically), the system will lack one-dimensional scanning and locking ability, and cannot determine the accurate position of the target in the elevation angle or azimuth angle, so it cannot realize reliable spatial positioning and beam intersection, and it is difficult to solve the inherent contradiction between scanning and measurement.

[0043] The embodiment adopts horizontally polarized leaky-wave antennas and vertically polarized leaky-wave antennas arranged orthogonally, and the system naturally obtains independent beam control capability in two orthogonal dimensions of azimuth and elevation, which provides necessary physical basis for subsequent two-stage working modes, i.e., first target scanning and positioning in a two-dimensional space, and then precise measurement through spatial intersection of double beams, thereby fundamentally solving the inherent contradiction between scanning and measurement of the leaky-wave antenna. In addition, the embodiment realizes two-dimensional electronic scanning and three-dimensional spatial positioning capability by using horizontally and vertically orthogonally arranged leaky-wave antennas with the simplest hardware, avoids using a complex and expensive two-dimensional phased array, and ensures system performance while extremely reducing cost. The embodiment has no mechanical moving parts and has a long service life; and beam control is realized through pure electronic means, which is quick and reliable.

[0044] The embodiment separates the two conflicting tasks in time through the two-stage mode of "scanning first and then measuring", so that the system can obtain extremely high phase stability in the vital sign monitoring stage, and fundamentally solves the contradiction between scanning and measurement, which is the key to detecting weak vital signs.

[0045] Further, in the embodiment, the signal processing module includes a three-dimensional inversion unit and a feature recognition unit.

[0046] The three-dimensional inversion unit is configured to perform phase recovery and energy reconstruction on the echo signal by using a range-azimuth-elevation joint inversion algorithm.

[0047] The feature recognition unit is configured to extract features of the generated three-dimensional energy map by using a deep learning or template matching method, for identifying spatial distribution and attitude features of multiple targets.

[0048] Further, in the embodiment, the monitoring module is further configured to detect phase changes caused by micro-movements of parts such as the chest and neck by using a phase perturbation micro-displacement measurement method, and extract the respiratory frequency and heartbeat frequency by using a fast Fourier transform (FFT) and a band-pass filtering algorithm, to realize non-contact vital sign monitoring.

[0049] Further, in the embodiment, the control module is further configured to realize system mode switching and resource scheduling based on a reinforcement learning algorithm, dynamically optimize the frequency scanning range and sampling rate by monitoring signal strength, noise level and energy consumption state in real time, to realize adaptive balance of energy consumption and calculation delay.

[0050] Further, in the embodiment, the system further includes a data fusion and visualization module, which is configured to fuse and display three-dimensional spatial perception results and vital sign data, generate a visual monitoring interface, and track multiple target states and trace historical data.

[0051] The non-contact vital sign detection system has the following advantages: 1. The contradiction between scanning and measuring is fundamentally solved: through the two-stage mode of "scanning first and measuring later", the two conflicting tasks are separated in time, so that the system can obtain high phase stability in the vital sign monitoring stage, which is the key to detecting weak vital signs.

[0052] 2. Two-dimensional scanning and three-dimensional positioning are realized at low cost: by using horizontally and vertically orthogonal leaky wave antennas, the system realizes two-dimensional electronic scanning and three-dimensional spatial positioning capability with the simplest hardware structure, avoiding the use of complex and expensive two-dimensional phased arrays, while ensuring system performance while reducing cost to the extreme.

[0053] 3. High system reliability: no mechanical moving parts, long service life; beam control is realized by pure electronic means, switching is fast and reliable.

[0054] 4. Energy concentration, high signal-to-noise ratio: in the monitoring stage, the double beams intersect at the target point, all the energy is continuously focused on the target point, and a signal-to-noise ratio comparable to high-end radar is obtained.

[0055] 5. Flexibility and intelligence: when the target moves beyond the current beam range, the system can automatically switch back to the first stage from the second stage, re-lock the target, and has adaptive tracking capability.

[0056] To achieve the above purpose, the present application also provides a non-contact vital sign detection method, which is applied to the non-contact vital sign detection system as described in the above embodiments, as shown in Figure 1 The method comprises the following steps: Step S10, in the target locking stage, control the horizontal polarization leaky wave antenna and the vertical polarization leaky wave antenna to perform coordinated frequency scanning in their respective dimensions, and perform omnidirectional two-dimensional detection on the monitoring area; Step S20, process the echo signal, and calculate the three-dimensional coordinates of at least one target to be measured in space through a direction of arrival estimation algorithm, the three-dimensional coordinates including azimuth angle, elevation angle and distance information; Step S30, in the vital sign monitoring stage, according to the three-dimensional coordinates of the target to be measured in space determined in the target locking stage, calculate the corresponding working frequencies required for the horizontal polarization leaky wave antenna and the vertical polarization leaky wave antenna to lock; Step S40, control the horizontal polarization leaky wave antenna to stop scanning, and fix its working frequency at the frequency corresponding to the azimuth angle; Step S50, control the vertical polarization leaky wave antenna to stop scanning, and fix its working frequency at the frequency corresponding to the elevation angle; Step S60, the beams of the horizontally polarized leaky-wave antenna and the vertically polarized leaky-wave antenna are made to intersect in space, and jointly and continuously irradiate the locked target point; Step S70, in the stable irradiation state, phase information of the echo is collected and analyzed, and a sign feature of the target is extracted through a phase demodulation algorithm, the sign feature including a breathing waveform and a heartbeat waveform.

[0057] In this embodiment, in the target locking stage, a two-dimensional MUSIC algorithm combined with distance FFT is used for three-dimensional coordinate estimation.

[0058] Specifically, in the step S20, a two-dimensional MUSIC algorithm combined with distance FFT is used for three-dimensional coordinate estimation. The step S20 includes: Step S201, constructing a signal model: the system scans at N frequency points, and the received signal is modeled as: x = α · a (θ, ϕ) + n (1) Wherein: x is a received signal vector; α is a complex amplitude, including a target reflection coefficient and a phase term e −j4πR / λ ; a(θ, ϕ) is an array steering vector, the elements of which represent the phase delay when electromagnetic waves arrive at each virtual array element from the direction (θ, ϕ); n is an additive noise vector; λ is the wavelength.

[0059] Step S202, covariance matrix calculation and decomposition: calculate the covariance matrix R xx =E[xx H ] of the received data, and perform eigenvalue decomposition on it, and divide the eigenvectors into a signal subspace U s and a noise subspace U n ; Step S203, spatial spectrum estimation and peak search: construct a two-dimensional MUSIC spatial spectrum function: P MUSIC (θ, ϕ) = 1 / aH(θ, ϕ)UnUHna(θ, ϕ) (2) Based on the orthogonal scanning characteristics of the horizontal and vertical antennas, through two-dimensional search in the azimuth and elevation angle dimensions, the peak position of the spectrum function P MUSIC is the estimated angle (θ peak , ϕ peak ) of the target. Step S204, distance estimation: perform fast Fourier transform on the echo signal, detect the position of the distance FFT spectrum peak, and calculate the accurate distance R of the target according to R=(c·∆t) / 2, wherein ∆t is the time delay; c is the speed of light.

[0060] In this embodiment, during the vital signs monitoring stage, the core is to use phase analysis and waveform extraction algorithms to demodulate the micro-motion signals caused by breathing and heartbeat from the stable echo phase.

[0061] Specifically, in this embodiment, the step of acquiring and analyzing the phase information of the echo in step S70 includes: Step S701, analyze the phase-displacement relationship: The baseband complex signal of the radar echo can be expressed as S(t) = I(t) + jQ(t) = Ae jϕ(t) Where I(t) is the real part, Q(t)s is the imaginary part, the total phase ϕ(t) = ϕ0 + ∆ϕ(t), ϕ0 = 4πR0 / λ is the initial phase, and ∆ϕ(t) is the time-varying phase caused by the thoracic displacement x(t), satisfying the following relationship: Δϕ(t) = (4π / λ)x(t) (3) Step S702, extract phase: Calculate the instantaneous phase: ϕ(t) = arctan2(Q(t), I(t)); Phase unwinding of ϕ(t) yields a continuous phase change ϕ. unwrapped (t); Subtracting the initial phase, we obtain the phase caused by the pure displacement: ∆ϕ(t)=ϕunwrapped(t)−ϕ0; Converted to a displacement signal: x(t) = (λ / 4π)·∆ϕ(t), which is the original thoracic cavity micromotion signal containing respiratory and heartbeat components.

[0062] In this embodiment, step S70 combines the breathing and heartbeat waveform extraction algorithm to separate breathing and heartbeat from the displacement signal x(t), and adopts an adaptive noise cancellation algorithm.

[0063] The step S70, which involves extracting the target's vital signs using a phase demodulation algorithm, includes: Step S703, Preprocessing: Bandpass filtering (e.g., 0.1-5 Hz) is applied to the displacement signal x(t) to remove DC and high-frequency noise. Step S704, Respiratory signal extraction: Use a low-pass filter (cutoff frequency ~0.8Hz) to directly extract the low-frequency, high-amplitude respiratory signal x from the displacement signal x(t). r (t); Step S705, Heartbeat signal extraction: The preprocessed displacement signal x(t) is used as the main input, which includes the strong respiratory signal x. r (t) and weak heartbeat signal x h (t); Extracted respiratory signal x r Using (t) as the reference input, a minimum mean square adaptive filter is employed, with the reference input x... r (t) is used to predict the respiratory component in the main input; Subtracting the filter output from the main input yields the error signal e(t) = x(t)−y(t), which is the purified heartbeat signal x. h (t).

[0064] Furthermore, in this embodiment, post-processing and parameter calculation steps are included after step S705.

[0065] Specifically, after step S705, the method further includes: Step S706, for the heartbeat signal x h (t) Perform fine bandpass filtering (e.g., 0.8-2.5 Hz); Step S707, respectively analyze the respiratory signal x r (t) and heartbeat signal x h (t) Perform spectral analysis or peak detection to calculate respiratory rate and heart rate.

[0066] The beneficial effects of the non-contact vital sign detection method of the present invention are: 1. It fundamentally solves the contradiction between scanning and measurement: By adopting a two-stage mode of "scan first, then measure", the two conflicting tasks are separated in time, enabling the system to achieve extremely high phase stability during the vital sign monitoring stage, which is the key to detecting weak vital signs.

[0067] 2. Achieving 2D scanning and 3D positioning at low cost: By using leaky wave antennas placed horizontally and vertically orthogonally, the system achieves 2D electronic scanning and 3D spatial positioning capabilities with the simplest hardware configuration, avoiding the use of complex and expensive 2D phased arrays, thus ensuring system performance while minimizing costs.

[0068] 3. High system reliability: No moving mechanical parts, long lifespan; beam control is achieved through pure electronic means, with rapid and reliable switching.

[0069] 4. Concentrated energy and high signal-to-noise ratio: During the monitoring phase, the dual beams converge in the target space, and all energy is continuously focused on the target point, achieving a signal-to-noise ratio comparable to that of high-end radars.

[0070] 5. Flexibility and intelligence: When the target moves out of the current beam range, the system can automatically switch from the second stage back to the first stage to re-lock the target, and has adaptive tracking capabilities.

[0071] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent structural transformations made under the concept of the present invention using the contents of the present invention specification and drawings, or direct / indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A non-contact vital sign detection system, characterized in that, include: A pair of orthogonally arranged microstrip leaky antennas: used for transmitting and receiving horizontally polarized and vertically polarized signals, respectively; Millimeter-wave signal transmitting module: connected to the microstrip leaky antenna, used to generate linear frequency modulated continuous wave signals and control the microstrip leaky antenna to perform frequency scanning within a set frequency range to form a virtual array and realize three-dimensional spatial energy distribution imaging; Signal processing module: used to perform range-azimuth-elevation joint inversion on echo signals during the target locking phase, generate a three-dimensional energy map, and identify the spatial three-dimensional coordinates, attitude, and location of multiple locked targets; Monitoring module: After the target is locked, during the vital signs monitoring phase, it is used to extract the target's vital signs information by using a small bandwidth frequency sweep or phase perturbation measurement near a fixed center frequency; The control module is used to coordinate the switching between the target locking phase and the vital signs monitoring phase, and to complete the timing control and data fusion.

2. The non-contact vital sign detection system according to claim 1, characterized in that, The pair of orthogonally arranged microstrip leaky antennas include: A horizontally polarized leaky antenna whose beam direction changes with frequency and scans in the azimuth dimension. A vertically polarized leaky antenna whose beam direction changes with frequency as it scans along the elevation dimension.

3. The non-contact vital sign detection system according to claim 2, characterized in that, The signal processing module includes a three-dimensional inversion unit and a feature recognition unit, wherein... The three-dimensional inversion unit is used to perform phase recovery and energy reconstruction of the echo signal using a range-azimuth-elevation joint inversion algorithm. The feature recognition unit is used to extract features from the generated three-dimensional energy map through deep learning or template matching methods, and is used to identify the spatial distribution and posture features of multiple targets.

4. The non-contact vital sign detection system according to any one of claims 1 to 3, characterized in that, The monitoring module is also used to detect phase changes caused by minute movements by employing a phase perturbation micro-displacement measurement method, and to extract respiratory and heart rates through fast Fourier transform and bandpass filtering algorithms to achieve non-contact vital sign monitoring.

5. The non-contact vital sign detection system according to claim 1, characterized in that, The control module is also used to realize system mode switching and resource scheduling based on reinforcement learning algorithms. By monitoring signal strength, noise level and energy consumption status in real time, it dynamically optimizes the frequency scanning range and sampling rate to achieve an adaptive balance between energy consumption and computing latency.

6. The non-contact vital sign detection system according to claim 1, characterized in that, The system also includes a data fusion and visualization module, which is used to fuse and display the three-dimensional spatial perception results with vital sign data, generate a visual monitoring interface, and perform multi-target status tracking and historical data tracing.

7. A non-contact method for detecting vital signs, characterized in that, The method is applied to the non-contact vital sign detection system as described in any one of claims 1 to 6, and the method includes the following steps: Step S10: During the target locking phase, control the horizontally polarized leaky antenna and the vertically polarized leaky antenna to perform cooperative frequency scanning in their respective dimensions to conduct all-round two-dimensional detection of the monitored area. Step S20: Process the echo signal and calculate the three-dimensional coordinates of at least one target in space using a direction of arrival estimation algorithm. The three-dimensional coordinates include azimuth, elevation and distance information. Step S30: In the vital signs monitoring stage, based on the three-dimensional coordinates of the target in space determined in the target locking stage, calculate the corresponding operating frequencies that the horizontally polarized leaky antenna and the vertically polarized leaky antenna need to lock. Step S40: Control the horizontally polarized leaky antenna to stop scanning and fix its operating frequency at the frequency corresponding to the azimuth angle; Step S50: Control the vertically polarized leaky antenna to stop scanning and fix its operating frequency at the frequency corresponding to the elevation angle; Step S60: The beams of the horizontally polarized leaky antenna and the vertically polarized leaky antenna intersect in space and continuously illuminate the locked target point together. Step S70: Under stable irradiation conditions, the phase information of the echo is collected and analyzed, and the vital signs of the target are extracted by the phase demodulation algorithm. The vital signs include respiratory and heartbeat waveforms.

8. The non-contact vital sign detection method according to claim 7, characterized in that, In step S20, a combination of two-dimensional MUSIC algorithm and distance FFT is used to estimate three-dimensional coordinates. Step S20 includes: Step S201, Constructing the signal model: Scanning at N frequency points, the received signal is modeled as follows: x = α·a(θ,ϕ)+n (1) Where: x is the received signal vector; α is the complex amplitude, including the target reflection coefficient and the phase term e determined by the distance R. −j4πR / λ a(θ, ϕ) is the array steering vector, whose elements characterize the phase delay of electromagnetic waves arriving at each virtual array element from the direction (θ, ϕ); n is the additive noise vector; λ is the wavelength. Step S202, Covariance Matrix Calculation and Decomposition: Calculate the covariance matrix R of the received data. xx =E[xx H ], and perform feature decomposition on it, dividing the feature vector into signal subspace U s and noise subspace U n ; Step S203, Spatial Spectrum Estimation and Peak Search: Constructing a Two-Dimensional MUSIC Spatial Spectrum Function: P MUSIC (θ,ϕ) = 1 / aH(θ,ϕ)UnUHna(θ,ϕ) (2) Based on the orthogonal scanning characteristics of horizontal and vertical antennas, the spectral function P is obtained through a two-dimensional search in the azimuth and elevation dimensions. MUSIC The peak position is the estimated angle of the target (θ). peak ϕ peak ); Step S204, distance estimation: Perform a fast Fourier transform on the echo signal, detect the position of the distance FFT spectrum peak, and calculate the precise distance R of the target according to R=(c·∆t) / 2, where ∆t is the time delay and c is the speed of light.

9. The non-contact vital sign detection method according to claim 8, characterized in that, The step of acquiring and analyzing the phase information of the echo in step S70 includes: Step S701, analyze the phase-displacement relationship: The baseband complex signal of the radar echo can be expressed as S(t) = I(t) + jQ(t) = Ae jϕ(t) Wherein, the total phase ϕ(t) = ϕ0 + ∆ϕ(t), ϕ0 = 4πR0 / λ is the initial phase, and ∆ϕ(t) is the time-varying phase caused by the thoracic displacement x(t), satisfying the following relationship: Δϕ(t) = (4π / λ)x(t) (3) Step S702, extract phase: Calculate the instantaneous phase: ϕ(t) = arctan2(Q(t), I(t)); Phase unwinding of ϕ(t) yields a continuous phase change ϕ. unwrapped (t); Subtracting the initial phase, we obtain the phase caused by the pure displacement: ∆ϕ(t)=ϕunwrapped(t)−ϕ0; Converted to displacement signal: x(t) = (λ / 4π)·∆ϕ(t), which is the original thoracic cavity micro-motion signal containing respiratory and heartbeat components; The step S70, which involves extracting the target's vital signs using a phase demodulation algorithm, includes: Step S703, Preprocessing: Perform bandpass filtering on the displacement signal x(t) to remove DC and high-frequency noise. Step S704, Respiratory signal extraction: Use a low-pass filter to directly extract the low-frequency, high-amplitude respiratory signal x from the displacement signal x(t). r (t); Step S705, Heartbeat signal extraction: The preprocessed displacement signal x(t) is used as the main input, which includes the strong respiratory signal x. r (t) and weak heartbeat signal x h (t); Extracted respiratory signal x r Using (t) as the reference input, a minimum mean square adaptive filter is employed, with the reference input x... r (t) is used to predict the respiratory component in the main input; Subtracting the filter output from the main input yields the error signal e(t) = x(t)−y(t), which is the purified heartbeat signal x. h (t).

10. The non-contact vital sign detection method according to claim 9, characterized in that, Following step S705, the following is also included: Step S706, for the heartbeat signal x h (t) Perform fine bandpass filtering; Step S707, respectively analyze the respiratory signal x r (t) and heartbeat signal x h (t) Perform spectral analysis or peak detection to calculate respiratory rate and heart rate.

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