Millimeter wave living body detection radar system

Abstract

The invention provides a millimeter wave living body detection radar system. The millimeter wave living body detection radar system comprises a millimeter wave transceiving antenna array, a transceiving front end, a frequency synthesis module, a radar control processing module and a display control computer. According to the invention, the technology of combining millimeter wave radar imaging and Doppler detection is adopted to detect insects carried in a luggage bag according to the detection requirement of the insects carried in the luggage bag; a Ka working frequency band is adopted, and the capability of penetrating materials such as foams, cartons and clothes is achieved; insects are detected by acquiring micro-Doppler information of a target and adopting a technology of combining millimeter-wave radar imaging and Doppler detection; the two-dimensional radar imaging capability and the original data storage capability are realized; a multiple-input multiple-output (MIMO) sparse array is used, compared with a real array, the number of antenna units used by the MIMO sparse array is far smaller than the number of image pixels, and cost and difficulty are reduced. The azimuth optimal resolution is less than or equal to 6mm, and the range resolution is less than or equal to 30mm.

Description

Technical Field

[0001] This invention relates to the field of measurement and testing technology, and specifically to a millimeter-wave liveness detection radar system. Background Technology

[0002] Customs officials measure insects during import and export quarantine, primarily to identify species, assess risks, and prevent the invasion of harmful alien species. However, effective detection methods are currently lacking.

[0003] Millimeter-wave radar is a type of radar that operates in the millimeter-wave band. Millimeter waves typically refer to the 30–300 GHz frequency range (wavelength 1–10 mm), with wavelengths between microwaves and centimeter waves. Millimeter-wave radar combines the advantages of microwave radar and photoelectric radar.

[0004] Therefore, a system that uses millimeter-wave radar to detect insects is needed. Summary of the Invention

[0005] This invention addresses the problem of insect detection by providing a millimeter-wave liveness detection radar system, comprising a millimeter-wave transceiver antenna array, a transceiver front-end, a frequency synthesis module, a radar control and processing module, and a display and control computer. Specifically designed for detecting insects tucked in luggage, this invention employs a combination of millimeter-wave radar imaging and Doppler detection technology. It utilizes the Ka band, enabling it to penetrate materials such as foam, cardboard, and clothing. By acquiring the target's micro-Doppler information, it combines millimeter-wave radar imaging and Doppler detection to detect insects. It features two-dimensional radar imaging capabilities and the ability to store raw data. The system uses a multiple-transmit, multiple-receive (MIMO) sparse array, which, compared to a solid array, uses far fewer antenna elements than image pixels, reducing cost and complexity. The optimal azimuth resolution of this invention is ≤6mm, and the range resolution is ≤30mm.

[0006] This invention provides a millimeter-wave liveness detection radar system, comprising a millimeter-wave transceiver antenna array, a transceiver front end, a frequency synthesis module, a radar control and processing module, and a display and control computer, which are connected in sequence. The antenna array includes at least two millimeter-wave radar antenna subarrays, each of which includes at least two transmitting antenna elements and at least two receiving antenna elements; the transmitting antenna elements transmit Ka-band signals, and the receiving antenna elements receive the echo Ka-band signals reflected from the target; The transceiver front end includes the same number of Ka-band transceiver modules as the number of millimeter-wave radar antenna subarrays. Each Ka-band transceiver module includes a transmitting unit and a receiving unit. The transmitting unit multiplies the signal output from the frequency synthesis module to obtain the Ka-band signal and then outputs it to the transmitting antenna unit. The receiving unit combines the echo signal output from the receiving antenna unit and mixes it with the local oscillator signal to obtain the intermediate frequency signal, which is then output to the radar control and processing module. The frequency synthesis module includes a connected C-band sweep frequency module and a Ku-band upconversion module. The C-band sweep frequency module generates a C-band Chirp signal, and the Ku-band upconversion module converts the C-band Chirp signal to a 10.4GHz~14GHz signal after doubling the frequency. The signal is then split into two outputs: one output to the local oscillator distribution network and the other output to the transmitting antenna unit. The frequency synthesis module also performs clock distribution. The radar control and processing module includes a signal acquisition and processing module for range pulse compression, BP kernel calculation, Doppler information calculation, and high-speed transmission, and a control module for receiving control, transmitting control, AD acquisition synchronization, and data processing synchronization. The range resolution of the millimeter-wave liveness detection radar system is ≤30mm. It can detect live bodies with a size of ≤30mm by acquiring BP imaging or Doppler information of the target.

[0007] In a preferred embodiment of the millimeter-wave liveness detection radar system described in this invention, each transmitting antenna unit corresponds to one transmitting channel, each receiving antenna unit corresponds to one receiving channel, and both transmitting and receiving antenna units are arranged in a square shape. The antenna array is a MIMO sparse array, which includes 6 millimeter-wave radar antenna subarrays. Each millimeter-wave radar antenna subarray includes 16 transmit antenna elements and 16 receive antenna elements.

[0008] In the millimeter-wave liveness detection radar system described in this invention, as a preferred embodiment, the maximum power of the receiving unit is: ; Among them, G t For the gain of the transmitting antenna element, G r For the gain of the receiving antenna element, P t λ is the transmission power, σ is the operating wavelength, σ is the radar cross section of the metal disk of the security scanner, and R is the optical path difference from the transmitting antenna to the target.

[0009] The millimeter-wave liveness detection radar system of the present invention, as a preferred embodiment, includes a C-band sweep frequency module comprising an FPGA connected to a signal acquisition and processing module, a digital-to-analog converter and a VCO connected in sequence to one output terminal of the FPGA, and a digital-to-analog converter, a bandpass filter and a frequency divider connected in sequence to the other output terminal of the FPGA, wherein the input terminal of the frequency divider is connected to the output terminal of the VCO and then connected to a Ku-band upconversion module; Range resolution is: ; Where c is the speed of light and B is the system bandwidth. κ The main lobe broadening factor is caused by the range-direction pulse compression window function; The main lobe broadening coefficient was adjusted by reducing the sidelobe to below -40dB and adding a Taylor window function during pulse compression. κ ; The sweep bandwidth of the VCO is obtained based on the system bandwidth B and the frequency multiplication factor; Pulse repetition period of C-band Chirp signal , among which, T scan N represents the data acquisition time for a single frame of imaging. TR This represents the total number of equivalent transmit and receive antenna elements; The C-band Chirp signal is generated to realize a single-line linear frequency modulated continuous wave signal with a bandwidth of 1.8 GHz, an output power of ≥0 dBm, a sweep period of 6 μs to 16 μs, and spurious emissions of -50 dBc.

[0010] The millimeter-wave liveness detection radar system of the present invention, as a preferred embodiment, includes the following steps in the BP kernel calculation method: S1, for each received signal Pulse compression is performed to obtain ,in, k For wave number, Let m be the coordinates of the transmission channel. Let be the coordinates of receiving channel n, and z be the Z coordinate of the projection position; S2, to BP focusing imaging was performed to obtain : ; in, This represents the distance from the launch channel to the projection position. Let j be the distance from the receiving channel to the projection position, and j be the imaginary part.

[0011] In a preferred embodiment of the millimeter-wave liveness detection radar system described in this invention, in step S1, ; in, δi For located The scattering coefficient of the target unit, This is the optical path difference from the electromagnetic wave illuminating the target through the transmitting antenna element.

[0012] In a preferred embodiment of the millimeter-wave liveness detection radar system described in this invention, the pulse compression of the ideal signal in step S1 is as follows: ; Where IFT stands for Fourier Transform. k Wave number; Based on ideal pulse compression, the dispersion of the channel is compensated by mixing with the reference channel, and the delay is compensated by multiplying by linear phase.

[0013] The millimeter-wave liveness detection radar system of the present invention, as a preferred embodiment, includes the following steps in its signal acquisition and processing module for Doppler information analysis: SⅠ. A set of matched filters is used on the receiving antenna of each millimeter-wave transceiver antenna array to process the received mixed signal. Each filter is matched to a specific transmitted waveform. , For the first Orthogonal signals transmitted through each transmission channel are received from each physical receiving channel according to their energy levels. Separate from Signals from different transmission channels ; SⅡ, all According to the virtual array element index Arranged to form a length of data vector Data vector For the received signal of the virtual array; SⅢ, Collect continuous pulses or time-domain snapshots over a specified period to obtain a length of... slow time series , The number of coherent processing intervals. The processing time for the Lth coherent; SⅣ, for slow time series Performing an FFT yields: ; The method for detecting living organisms with a size of 30 mm or less using Doppler information is as follows: when a velocity of... v When the target is reached, then in all M×N virtual channels In the middle, they are all at the same Doppler frequency. A peak value appears at λ, where λ is the operating wavelength.

[0014] In a preferred embodiment of the millimeter-wave liveness detection radar system described in this invention, in step SⅠ, at the first... On each receiving channel, the echo signal from the target, after down-conversion to baseband, is as follows: ; Where α is the complex amplitude, which includes the target scattering coefficient and path loss; The transmitted waveform has a time delay The waveform afterward; For the Doppler frequency shift term, where ; For from the first m The transmission spatial phase from each transmitting antenna to the target; To go from the goal to the first n The spatial phase of each receiving antenna.

[0015] ; in, It is a convolution; since the waveforms are orthogonal, the output energy is maximized when the filter matches its own waveform; when it matches other waveforms, the output is zero.

[0016] In a preferred embodiment of the millimeter-wave liveness detection radar system described in this invention, the display and control computer is connected to the radar control and processing module via a fiber optic interface, and performs liveness detection by issuing detection commands and receiving returned liveness detection information.

[0017] This invention addresses the need for detecting insects tucked in luggage by employing a combination of millimeter-wave radar imaging and Doppler detection technology to achieve insect detection.

[0018] The present invention has the following advantages: This invention uses the Ka band, which has the ability to penetrate materials such as foam, cardboard boxes, and clothing; by acquiring the micro-Doppler information of the target, it uses a combination of millimeter-wave radar imaging and Doppler detection technology to detect insects; it has two-dimensional radar imaging capabilities and the ability to store raw data; it uses a multiple-transmit multiple-receive (MIMO) sparse array, which, compared to a real array, uses far fewer antenna elements than the number of image pixels, reducing cost and complexity. Attached Figure Description

[0019] Figure 1 A structural block diagram of a millimeter-wave liveness detection radar system; Figure 2 This is a schematic diagram of a millimeter-wave radar antenna subarray for a millimeter-wave liveness detection radar system. Figure 3A flowchart illustrating the workflow of a millimeter-wave liveness detection radar system; Figure 4 A functional block diagram of a C-band frequency sweeping module for a millimeter-wave liveness detection radar system; Figure 5 This is a schematic diagram of a Ku-band channel frequency multiplication module for a millimeter-wave liveness detection radar system. Figure 6 This is a schematic diagram of the transmitting front-end module of a millimeter-wave liveness detection radar system. Figure 7 This is a schematic diagram of the receiving front-end module of a millimeter-wave liveness detection radar system. Figure 8 This is a functional block diagram of the signal acquisition and processing module of a millimeter-wave liveness detection radar system. Figure 9 This is a functional block diagram of the control module of a millimeter-wave liveness detection radar system.

[0020] Figure label: 1. Antenna array; 11. Transmitting antenna unit; 12. Receiving antenna unit; 2. Transceiver front end; 3. Frequency synthesis module; 31. C-band sweep frequency module; 32. Ku-band up-conversion module; 4. Radar control and processing module; 41. Signal acquisition and processing module; 42. Control module; 5. Display and control computer. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example 1

[0022] like Figures 1-9 As shown in the accompanying drawings, a millimeter-wave liveness detection radar system is described in further detail, taking a millimeter-wave liveness detection radar with an optimal azimuth resolution of ≤6mm and a range resolution of ≤30mm as an example.

[0023] like Figure 1 The diagram shows a block diagram of a millimeter-wave liveness detection radar system, which mainly consists of a millimeter-wave transceiver antenna array 1, a transceiver front-end 2, a frequency synthesis module 3, a radar control and processing module 4, and a display and control computer 5.

[0024] like Figure 2 The diagram shows a millimeter-wave transceiver antenna array 1.

[0025] like Figure 3 The diagram shows the workflow of a millimeter-wave liveness detection radar.

[0026] like Figure 4The C-band sweep frequency module 31 shown is used to generate C-band Chirp signals and perform up-conversion.

[0027] like Figure 5 This is a schematic diagram of a Ku-band upconverter module 32, which is mainly used for frequency multiplication, transmission distribution, local oscillator distribution, and clock distribution.

[0028] Figure 6 This is a block diagram of the transmitter front-end module, used to distribute the transmitted signal.

[0029] Figure 7 This is a block diagram of the receiving front-end module, used to collect the received signal and mix it with the local oscillator signal to obtain the intermediate frequency signal.

[0030] Figure 8 , Figure 9 The radar control and processing module is a functional block diagram used for acquiring and processing intermediate frequency signals and for system control.

[0031] The functions of each module will be described in detail below.

[0032] Antenna Array 1: To meet the requirements of imaging range and resolution, the millimeter-wave radar antenna array comprises six subarrays. Each subarray contains 16 receiving antenna elements 12 and 16 transmitting antenna elements 11, arranged in a U-shape, such as... Figure 2 As shown, blue represents the transmitting antenna element and red represents the receiving antenna element. Each transmitting antenna element 11 corresponds to one transmitting channel, and each receiving antenna element 12 corresponds to one receiving channel.

[0033] Frequency synthesis module 3: Frequency synthesis module 3 mainly includes C-band sweep frequency module 31 and Ku-band upconversion module 32.

[0034] Spatial resolution in the range direction can be calculated using the following formula: ; In the formula, c is the speed of light, and B is the system bandwidth. κ This is the main lobe broadening coefficient caused by the range-direction pulse compression window function.

[0035] The required spatial resolution in the range direction is 30mm. To reduce the sidelobes to below -40dB, a Taylor window function is added during pulse compression, which broadens the main lobe by approximately 1.2 times. This allows us to calculate a system bandwidth of 6GHz. Considering the frequency multiplication factor of 4 in the terahertz transceiver link, the sweep bandwidth of the VCO frequency sweep can be calculated to be at least 1.5GHz.

[0036] The FMCW pulse repetition period mainly depends on the azimuth sampling rate on the time axis, and the pulse repetition period can be expressed as: ; In the formula T scan N represents the data acquisition time for a single frame of imaging. TR This represents the equivalent number of transmit and receive antenna elements.

[0037] In this system, T scan <5ms, N TR =192, and the longest pulse repetition period can be calculated to be approximately 26μs. Assuming the switching time of the transmitting unit is <250ns (on / off), the pulse width can be designed to be 16μs, the pulse repetition period can be set to 16.5μs, and the single-frame imaging data acquisition time is 5ms, which meets the design requirements.

[0038] The generation of C-band Chirp signals requires a single-line linear frequency modulated continuous wave signal with a bandwidth of 1.8 GHz, an output power of ≥0 dBm, a sweep period of 6 μs to 16 μs, and spurious emissions of -50 dBc.

[0039] The Ku-band channel frequency multiplier module mainly consists of five parts: frequency multiplication, transmit distribution, local oscillator distribution, and clock distribution. Its main functions are as follows: 1) The C-band frequency sweep module 31 is multiplied by 2 to reach 10.4GHz~14GHz, and then outputs in two paths. One path is sent to the local oscillator distribution network, and the other path is sent to the transmitter distribution network.

[0040] 2) The uplink RF signal is transmitted to the RF front-end after being split into 6 channels by a delay line (RF cable, 1.25m). The uplink LO signal is directly input to the local oscillator distribution network and then split into 6 channels before being transmitted to the RF front-end.

[0041] Ka-band transceiver front-end 2: Ka-band transceiver front-end 2 has a total of 6 Ka-band transceiver modules, each module has 16 transceiver units, corresponding to 16 transmit antennas and 16 receive antennas.

[0042] The target echo signal power can be calculated using radar equations. When calculating, the size of the target is taken into account, and a metal disk with a distance of 1.0m and a diameter of 0.3m is selected as the reference for the part with the strongest reflection.

[0043] In a Ka-band security scanner system, the RCS of the metal disc is: ; According to the radar equations, the maximum power of the receiving front end can be calculated as follows: ; Considering the current antenna G t and G r Both are 5dB, assuming feeder loss G loss The power reaching the receiver front end is 3dB. Set the transmit power. The P1dB of the front-end input is -15.5dBm, and the P1dB of the output is 4dBm. Therefore, the receiver gain must be 19.5dBc to ensure that the output meets the AD sampling requirements.

[0044] Radar Control and Processing Module 4: The radar control and processing module mainly includes a signal acquisition and processing module 41 and a control module 42. The signal acquisition and processing module 41 comprises three parts: range pulse compression (including DDC down-conversion, IFFT, delay correction, and phase correction), BP kernel calculation, and high-speed transmission. The echo signal can be represented as: ; In the formula k For wave number, For the coordinates of the transmitting unit, For the coordinates of the receiving unit, For located The scattering coefficient of the target unit, This is the optical path difference from the transmitting antenna to the target.

[0045] The BP imaging algorithm mainly includes the following two steps: (1) For the signal of each receiving channel Pulse compression, specifically pulse compression of an ideal signal, can be expressed as: ; In reality, channels exhibit dispersion and group delay. During pulse compression, the dispersion of the channel needs to be compensated by mixing with a reference channel, and the delay needs to be compensated by multiplying by a linear phase.

[0046] (2) To Perform BP focusing imaging: ; In the formula The distance from the transmitting unit to the projection position is [missing information]. This represents the distance from the receiving unit to the projection position. The BP coefficient is mainly determined through a lookup table.

[0047] (3) Assume a target with a radial velocity of .

[0048] No. The orthogonal signals transmitted by the transmitting antennas are .

[0049] In the On each receiving antenna, the echo signal from the target (after down-conversion to baseband) can be represented as: ; Formula Explanation: Complex amplitude, including target scattering coefficient, path loss, etc.

[0050] The transmitted waveform has a time delay. The later version.

[0051] The Doppler frequency shift term is the core of velocity detection, in which... , For wavelength, For speed.

[0052] From the first The transmission spatial phase from each transmitting antenna to the target.

[0053] From the goal to the first The spatial phase of each receiving antenna.

[0054] On each receiving antenna, a set of matched filters is used (each filter matches a specific transmit waveform). To process the received mixed signals.

[0055] ; in This represents convolution. Because the waveforms are orthogonal, when the filter matches its own waveform (…), s m right s m ), with maximum output energy; matched to other waveforms ( s m right s k ,k≠m When ), the output is almost zero.

[0056] Thus, from each physical receive channel In, it was separated Signals from different transmission channels .

[0057] All According to the virtual array element index Arrange them to form a long data vector. Its length is This vector represents the received signal of the virtual array.

[0058] To detect moving targets, it is necessary to analyze how the signal changes over time. We collect a series of continuous pulses (or time-domain snapshots).

[0059] Assuming that it was collected Data processed at coherent intervals (CPI). For each virtual element We have a length of Slow time series: ; For this slow time series Perform FFT (Pulse Doppler) processing: ; If there exists a velocity of The goal, then in all One virtual channel In the middle, they will all be at the same Doppler frequency. A peak appears at that point.

[0060] The control module 42 mainly implements functions such as receiving control, transmitting control, AD acquisition synchronization, and data processing synchronization of the front-end chip.

[0061] External display and control unit: The external display and control unit is used to monitor the liveness detection status and is connected to the signal acquisition and processing module via a fiber optic interface. It performs liveness detection by issuing detection commands and receiving returned liveness detection information.

[0062] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A millimeter-wave liveness detection radar system, characterized in that: It includes a millimeter-wave transceiver antenna array (1), a transceiver front end (2), a frequency synthesis module (3), a radar control and processing module (4), and a display and control computer (5) that are connected in sequence. The antenna array (1) includes at least two millimeter-wave radar antenna subarrays, each of which includes at least two transmitting antenna elements (11) and at least two receiving antenna elements (12); the transmitting antenna elements (11) transmit Ka-band signals, and the receiving antenna elements (12) receive Ka-band echo signals reflected from the target; The transceiver front end (2) includes a number of Ka-band transceiver modules that are the same as the number of millimeter-wave radar antenna subarrays. Each Ka-band transceiver module includes a transmitting unit and a receiving unit. The transmitting unit multiplies the signal output by the frequency synthesis module (3) to obtain a Ka-band signal and then outputs it to the transmitting antenna unit (11). The receiving unit combines the echo signal output by the receiving antenna unit (12) and mixes it with the local oscillator signal to obtain an intermediate frequency signal, which is then output to the radar control and processing module (4). The frequency synthesis module (3) includes a connected C-band sweep frequency module (31) and a Ku-band upconversion module (32). The C-band sweep frequency module (31) generates a C-band Chirp signal. The Ku-band upconversion module (32) converts the C-band Chirp signal to a 10.4GHz~14GHz signal after doubling the frequency. The signal is then split into two outputs: one output to the local oscillator distribution network and the other output to the transmitting antenna unit (11). The frequency synthesis module (3) also performs clock distribution. The radar control and processing module (4) includes a signal acquisition and processing module (41) for range pulse compression, BP kernel calculation, Doppler information calculation, and high-speed transmission, and a control module (42) for receiving control, transmitting control, AD acquisition synchronization, and data processing synchronization. The range resolution of the millimeter-wave liveness detection radar system is ≤30mm. It can detect live bodies with a size of ≤30mm by acquiring BP imaging or Doppler information of the target.

2. The millimeter-wave liveness detection radar system according to claim 1, characterized in that: Each of the transmitting antenna units (11) corresponds to one transmitting channel, and each of the receiving antenna units (12) corresponds to one receiving channel. Each of the transmitting antenna units (11) and each of the receiving antenna units (12) are arranged in a square shape. The antenna array (1) is a MIMO sparse array, and the antenna array (1) includes 6 millimeter-wave radar antenna subarrays, each of which includes 16 transmitting antenna elements (11) and 16 receiving antenna elements (12).

3. The millimeter-wave liveness detection radar system according to claim 1, characterized in that: The maximum power of the receiving unit is: ； Among them, G t For the transmit antenna element gain, G r For the gain of the receiving antenna element, P t λ is the transmission power, σ is the operating wavelength, σ is the radar cross section of the metal disk of the security scanner, and R is the optical path difference from the transmitting antenna to the target.

4. The millimeter-wave liveness detection radar system according to claim 1, characterized in that: The C-band sweep frequency module (31) includes an FPGA connected to the signal acquisition and processing module (41), a digital-to-analog converter and a VCO connected in sequence to one output terminal of the FPGA, and a digital-to-analog converter, a bandpass filter and a frequency divider connected in sequence to the other output terminal of the FPGA. The input terminal of the frequency divider is connected to the output terminal of the VCO and then connected to the Ku-band upconversion module (32). Range resolution is: ； Where c is the speed of light and B is the system bandwidth. κ The main lobe broadening factor is caused by the range-direction pulse compression window function; The main lobe broadening coefficient was adjusted by reducing the sidelobe to below -40dB and adding a Taylor window function during pulse compression. κ ; The sweep bandwidth of the VCO is obtained based on the system bandwidth B and the frequency multiplication factor; Pulse repetition period of C-band Chirp signal , among which, T scan N represents the data acquisition time for a single frame of imaging. TR This represents the total number of equivalent transmit and receive antenna elements; The C-band Chirp signal is generated to realize a single-line linear frequency modulated continuous wave signal with a bandwidth of 1.8 GHz, an output power of ≥0 dBm, a sweep period of 6 μs to 16 μs, and spurious emissions of -50 dBc.

5. A millimeter-wave liveness detection radar system according to claim 1, characterized in that: The BP kernel calculation method includes the following steps: S1, for each received signal Pulse compression is performed to obtain ,in, k For wave number, Let m be the coordinates of the transmission channel. Let be the coordinates of receiving channel n, and z be the Z coordinate of the projection position; S2, to BP focusing imaging was performed to obtain : ； in, This represents the distance from the launch channel to the projection position. Let j be the distance from the receiving channel to the projection position, and j be the imaginary part.

6. A millimeter-wave liveness detection radar system according to claim 5, characterized in that: In step S1, in, δ i For located The scattering coefficient of the target unit, This is the optical path difference from the electromagnetic wave illuminating the target through the transmitting antenna element.

7. A millimeter-wave liveness detection radar system according to claim 6, characterized in that: In step S1, the pulse compression of the ideal signal is as follows: ； Where IFT stands for Fourier Transform. k Wave number; Based on ideal pulse compression, the dispersion of the channel is compensated by mixing with the reference channel, and the delay is compensated by multiplying by linear phase.

8. A millimeter-wave liveness detection radar system according to claim 1, characterized in that: The method for Doppler information analysis by the signal acquisition and processing module (41) includes the following steps: SⅠ. A set of matched filters is used on the receiving antenna of each of the millimeter-wave transceiver antenna arrays (1) to process the received mixed signal. Each filter is matched to a specific transmitted waveform. , For the first Orthogonal signals transmitted through each transmission channel are received from each physical receiving channel according to their energy levels. Separate from Signals from different transmission channels ; SⅡ, all According to the virtual array element index Arranged to form a length of data vector The data vector For the received signal of the virtual array; SⅢ, Collect continuous pulses or time-domain snapshots over a specified period to obtain a length of... slow time series , The number of coherent processing intervals. The processing time for the Lth coherent; SⅣ, for slow time series Performing an FFT yields: ； The method for detecting living organisms with a size of 30 mm or less using Doppler information is as follows: when a velocity of... v When the target is reached, then in all M×N virtual channels In the middle, they are all at the same Doppler frequency. A peak value appears at λ, where λ is the operating wavelength.

9. A millimeter-wave liveness detection radar system according to claim 8, characterized in that: In step SⅠ, at the first On each receiving channel, the echo signal from the target, after down-conversion to baseband, is as follows: ； Where α is the complex amplitude, which includes the target scattering coefficient and path loss; The transmitted waveform has a time delay The waveform afterward; For the Doppler frequency shift term, where ; For from the first m The transmission spatial phase from each transmitting antenna to the target; To go from the goal to the first n The spatial phase of each receiving antenna: ； in, It is a convolution; since the waveforms are orthogonal, the output energy is maximized when the filter matches its own waveform; when it matches other waveforms, the output is zero.

10. A millimeter-wave liveness detection radar system according to claim 1, characterized in that: The display and control computer (5) is connected to the radar control and processing module (4) through a fiber optic interface, and performs liveness detection by issuing detection commands and receiving the returned liveness detection information.

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