A high spatio-temporal resolution millimeter wave radar imaging system

Abstract

This invention discloses a high spatiotemporal resolution millimeter-wave radar imaging system, comprising: a U-shaped antenna array module, wherein the transmitting and receiving antennas are symmetrically distributed in a U-shape, with an element spacing greater than or equal to half a wavelength, adapted to the SAR imaging mechanism, and using an electronic scanning scheme to achieve beam scanning; a radio frequency (RF) module, employing a cyclic one-transmit-multiple-receive mode, completing data acquisition for all transmitting and receiving channels by cyclically switching the transmitting elements to ensure high system refresh rate and spatiotemporal resolution; a signal processing module, receiving multi-channel echo signals, rearranging the echo signals, and using a hardware-parallel accelerated time-domain backpropagation (BP) algorithm for imaging; and a control module, using a microcontroller to control the RF chip of the RF module. This invention verifies the applicability of antenna spacing greater than or equal to half a wavelength in near-field SAR imaging mechanisms, overcomes the dependence of traditional MIMO systems on antenna half-wavelength spacing, achieves high spatiotemporal resolution near-field imaging, and reduces system complexity and cost.

Description

Technical Field

[0001] This invention relates to the field of millimeter-wave radar hardware system technology, and in particular to a high spatiotemporal resolution millimeter-wave radar imaging system. Background Technology

[0002] Millimeter-wave radar, as a core component for high-precision environmental perception, is widely used in intelligent transportation, industrial inspection, and security monitoring. Its spatiotemporal resolution, imaging quality, and degree of engineering directly determine its adaptability to various application scenarios. With technological advancements, the U-shaped array, capable of simultaneously covering both horizontal and elevation two-dimensional detection, has become an important structural form for acquiring three-dimensional high-resolution imaging results.

[0003] Existing U-shaped array radar systems all employ a Multiple-Input Multiple-Output (MIMO) architecture, using waveform diversity to create a virtual aperture and improve resolution. However, constrained by the Nyquist sampling theorem, traditional MIMO systems require the antenna element spacing to be less than or equal to half a wavelength; otherwise, aliasing between echoes will occur, leading to angle measurement errors. This constraint significantly increases the integration difficulty of the antenna array, as well as the system cost and complexity. Furthermore, the binding of the MIMO architecture to the U-shaped array makes it difficult for existing systems to balance imaging accuracy and real-time performance, resulting in poor adaptability to near-field high-resolution scenarios requiring high refresh rates.

[0004] Synthetic Aperture Radar (SAR) is a technology that uses the relative motion between a target and a radar to create a virtual aperture, thereby acquiring high-resolution azimuth images. SAR imaging, based on the principle of synthetic aperture, can improve angular resolution without increasing the number of physical antennas, offering advantages such as strong anti-interference capabilities and high imaging quality. However, there is currently no imaging scheme that combines a U-shaped array with the SAR system.

[0005] In summary, how to reduce the integration difficulty and system cost of a U-shaped array while meeting spatial sampling constraints, and simultaneously improve imaging resolution and data refresh rate, is a technical challenge faced by those skilled in the art. Existing technical solutions have shortcomings in one or more of the above aspects, and have not yet formed a complete solution that balances imaging accuracy, real-time performance, system complexity, and engineering feasibility. Summary of the Invention

[0006] Purpose of the invention: The purpose of this invention is to provide a high spatiotemporal resolution millimeter-wave radar imaging system that combines SAR imaging mechanism with a sparse array to achieve high-resolution near-field imaging while reducing system complexity and cost.

[0007] Technical solution: To achieve the above-mentioned objectives, the present invention provides a high spatiotemporal resolution millimeter-wave radar imaging system, comprising:

[0008] The U-shaped antenna array module consists of a transmitting antenna array and a receiving antenna array, which are symmetrically distributed in a U-shape. The interval between the transmitting antenna elements and the receiving antenna elements is greater than or equal to half a wavelength, which is compatible with the SAR imaging mechanism and can achieve beam scanning in conjunction with the electronic scanning scheme.

[0009] The radio frequency module adopts a cyclic one-transmit-multiple-receive mode. In each round of transmitting and receiving radio frequency signals, one transmitting array element transmits the signal and multiple receiving array elements receive the echo signal. Data acquisition of all transmitting and receiving channels is completed by cyclically switching the transmitting array element.

[0010] The signal processing module is used to receive multi-channel echo signals, rearrange the echo signals, and perform imaging using a hardware-parallel accelerated back projection (BP) algorithm in the time domain.

[0011] The control module uses a microcontroller to control the RF chip of the RF module.

[0012] Preferably, in the U-shaped antenna array module, the transmitting antenna array includes two parts, one above and one below, and the other left and right, and the receiving antenna array includes two parts, one left and one right, and the other above and one below.

[0013] Preferably, the radio frequency module includes N radio frequency chips, each radio frequency chip integrating P transmit channels and Q receive channels; the N radio frequency chips together constitute NP transmit channels and NQ receive channels; the NQ analog signal echoes of the receive channels are uniformly digitally sampled by the AD sampling module.

[0014] Preferably, the cyclic one-to-many transmit / receive mode is implemented as follows: a microcontroller cyclically controls the RF chip's transmit and receive operations, with each cycle controlling one transmitting element to transmit a signal and M receiving elements to receive echo signals; collecting complete NQ channels of signals requires transmission from the same transmitting element. Secondary radar signals, among which This represents the rounding up operator; the microcontroller switches and controls the transmitting array elements, cyclically acquiring data NP times to obtain the final NP×NQ radar echo signals.

[0015] Preferably, the adaptation method of the U-shaped antenna array to the SAR imaging mechanism is to simulate the spatial motion of the transmitting antenna by electronic scanning switching, construct an equivalent synthetic aperture, and process the echo signal received by the array using the SAR imaging algorithm to achieve three-dimensional imaging.

[0016] Preferably, before imaging the echo signal, the projection relationship is adjusted according to the spatial position between the target and the U-shaped antenna array, and the acquired echo data is preprocessed to adapt to the subsequent time-domain BP algorithm, specifically expressed as follows:

[0017] ;

[0018] in Represents the radar-acquired signal of a single target. Indicates slow time. To save time, and This indicates the position coordinates of the transmitting and receiving antennas. This indicates rearrangement of the echo signal. This represents the data rearrangement operator, which is used to determine the transmit antenna number and receive antenna number in the acquisition timing sequence according to the timing configuration of the cyclic one-to-many transmission mode, and fill the acquired signal into a three-dimensional matrix with the transmit antenna number as the row dimension, the receive signal number as the column dimension, and the AD sampling number as the third dimension.

[0019] Preferably, a time-domain backpropagation (BP) algorithm is used for 3D imaging. The first step is to perform phase compensation on the distance-focused signal, and the second step is to interpolate and accumulate the coherent signals. The overall imaging process is represented as follows:

[0020] ;

[0021] in This represents the signal after data rearrangement and interpolation. The position coordinates are The sum of the distances from each grid point to the receiving and transmitting antennas is expressed as:

[0022] ;

[0023] and These are the position coordinates of the transmitting and receiving antennas, respectively; the phase compensation filter is represented as...

[0024] ;

[0025] in An exponential function with the natural constant as its base. represents an imaginary number, Here, c represents the carrier frequency, and c represents the speed of light. This represents the final image. , These represent the upper and lower limits of the y-coordinate of the receiving antenna, respectively. , These represent the upper and lower limits of the x-coordinate of the transmitting antenna, respectively.

[0026] As a preferred method, the accumulation of data for each transmitting and receiving antenna is performed in parallel during the imaging process, using hardware acceleration to accumulate multiple slow-time sampling points simultaneously.

[0027] Preferably, in each round of transmission and reception of the radar imaging system, the signal source first generates a local oscillator signal to the radio frequency chip. After receiving the local oscillator signal, the radio frequency chip transmits a millimeter-wave signal. After receiving the echo signal, the radio frequency chip receives the echo signal and samples it using an analog-to-digital converter (ADC) chip. After data sampling, the data is transmitted to a field programmable gate array (FPGA) chip. The FPGA chip converts the sampled echo signal and transmits it to the signal processing module for data storage.

[0028] Preferably, in the control module, the microcontroller is responsible for controlling the signal source and the FPGA chip, thereby controlling the sequence of signal transmission, signal acquisition and data storage of the entire system; the control signal of the RF chip is output by the microcontroller, and the four RF chips are grouped together; the microcontroller first transmits the control signal to the signal source, the signal source transmits the signal to the RF chip, then the microcontroller controls the RF chip to complete the transmission and reception process, and finally the microcontroller controls the FPGA chip to receive and store the ADC sampling signal.

[0029] Beneficial effects: Compared with the prior art, the present invention has the following significant effects:

[0030] 1. This invention combines the SAR imaging mechanism with a sparse array in the shape of a square, and relaxes the antenna element spacing to more than or equal to half a wavelength, breaking through the limitation of the traditional MIMO system that the antenna element spacing must be less than or equal to half a wavelength, thus reducing the integration difficulty of the antenna array and the system cost.

[0031] 2. Compared to traditional mechanical scanning methods, which require a longer time to acquire data per round, this invention achieves a high refresh rate for system imaging—reaching 10Hz or higher—through an electronic scanning combined with a cyclic transmit-receive-multiple-receive mode. Furthermore, this invention employs a SAR imaging mechanism with an antenna spacing greater than or equal to half a wavelength. With the same number of antenna elements, a longer aperture can be obtained, enabling higher spatial resolution imaging, achieving sub-centimeter resolution in both azimuth and lateral dimensions.

[0032] 3. In the signal processing module, this invention rearranges the data and uses a hardware-parallel accelerated time-domain BP algorithm for imaging, which can achieve fast and high-precision imaging while being compatible with the U-shaped array.

[0033] 4. This invention provides a complete and engineering-feature-feature-feature-resolved high spatiotemporal resolution radar imaging system, which combines the advantages of high resolution, high refresh rate, low cost and low complexity, and is suitable for near-field high-precision imaging application scenarios. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the system structure according to an embodiment of the present invention;

[0036] Figure 2 This is a schematic diagram of the chip distribution in an embodiment of the present invention;

[0037] Figure 3 This is a schematic diagram of chip grouping in an embodiment of the present invention;

[0038] Figure 4 This is a diagram showing the chip grouping and numbering in an embodiment of the present invention;

[0039] Figure 5 This is a timing diagram of the cyclic one-to-many transmit / receive mode in an embodiment of the present invention;

[0040] Figure 6 This is a simulation diagram of the vertical polarization gain of a single antenna in this invention;

[0041] Figure 7 This is a simulation diagram of the horizontal polarization gain of a single antenna in this invention.

[0042] Figure 8 The image shows a simulated slice of the antenna spacing in an embodiment of the present invention, with each slice having an antenna spacing of 0.5 times the wavelength.

[0043] Figure 9 The image shows a simulated slice of the antenna spacing of 0.75 times the wavelength in an embodiment of the present invention.

[0044] Figure 10 This is a simulation slice diagram showing the antenna spacing as a single wavelength in an embodiment of the present invention;

[0045] Figure 11 The image shows a simulated slice of the antenna spacing, which is 1.25 times the wavelength, in an embodiment of the present invention.

[0046] Figure 12 The image shows a simulated slice of the antenna spacing, which is 1.5 times the wavelength, in an embodiment of the present invention.

[0047] Figure 13 This is a simulation 3D result diagram from an embodiment of the present invention. Detailed Implementation

[0048] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0049] This invention provides a high spatiotemporal resolution millimeter-wave radar imaging system, mainly comprising a U-shaped antenna array module, a radio frequency (RF) module, a signal processing module, and a control module. The U-shaped antenna array module consists of a transmitting antenna array and a receiving antenna array, symmetrically distributed in a U-shape. The spacing between the transmitting and receiving antenna elements is greater than or equal to half a wavelength, adapting to the SAR imaging mechanism and enabling beam scanning in conjunction with an electronic scanning scheme. The RF module employs a cyclic one-transmit-multiple-receive mode, where one transmitting element transmits a signal and multiple receiving elements receive the echo signals in each round of RF signal transmission and reception. Data acquisition for all transmission and reception channels is completed by cyclically switching the transmitting element. The signal processing module receives multi-channel echo signals, rearranges the echo signals, and uses a hardware-parallel accelerated time-domain backpropagation (BP) algorithm for imaging. The control module uses a microcontroller to control the RF chip of the RF module.

[0050] In this embodiment, a high refresh rate for system imaging is achieved through electronic scanning combined with a cyclic one-to-many transmission and multiple-receiver mode. Furthermore, by employing a SAR imaging mechanism with an antenna spacing greater than or equal to half a wavelength, a longer aperture can be obtained with the same number of antenna elements. A longer aperture enables imaging with higher spatial resolution. The following section will combine... Figure 1 Each module is described in detail.

[0051] 1. U-shaped antenna array module

[0052] In this embodiment, the spacing between the transmitting antenna element and the receiving antenna element is greater than or equal to half a wavelength. With the same number of antenna elements, a larger antenna spacing can create a longer aperture, which in turn enables higher resolution imaging. Specifically, in a U-shaped antenna array module, the transmitting antenna array comprises two parts: top and bottom (or left and right), and the receiving antenna array comprises two parts: left and right (or top and bottom). In this embodiment, the transmitting antenna array is distributed in the left and right parts of the module, and the receiving antenna array is distributed in the top and bottom parts of the module, as an example.

[0053] After simulating and verifying the imaging performance of the U-shaped array, the system scheme was determined to be a scheme using chips capable of transmitting analog signals plus external high-speed AD sampling. Taking sixteen chips with three transmit and four receive terminals, and a three-quarter wavelength spacing as an example (see figure)... The final chip distribution diagram is as follows: Figure 2 As shown in the figure, the gray area is the radio frequency board, the smaller brown squares are the antenna transceiver elements, and the larger yellow squares are the radio frequency chips.

[0054] 2. Radio Frequency Module

[0055] In this embodiment, the RF module adopts a cyclic one-transmit-multiple-receive mode, completing data acquisition for all transmit and receive channels by cyclically switching the transmit array elements to ensure high system refresh rate and spatiotemporal resolution. Specifically, the RF module includes N RF chips, each integrating P transmit channels and Q receive channels; the N RF chips together constitute NP transmit channels and NQ receive channels; the NQ analog signal echoes of the receive channels are uniformly digitally sampled by the AD sampling module.

[0056] In practical applications, the implementation of the RF module transceiver link can be as follows: adopting a cyclic one-to-many transmission mode, in each round of transmission and reception, the signal source first generates a local oscillator signal to the RF chip, the RF chip transmits a microwave signal after receiving the local oscillator signal, the RF chip receives the echo signal and the ADC chip samples it, the sampled data is transmitted to the FPGA chip, the FPGA chip converts the sampled echo signal into a form that is easy to store after data conversion, and finally transmits it to the signal processing module for data storage.

[0057] Specifically, based on the principle of cyclic one-to-many transmission and multiple-to-receive and the chip numbering grouping, the cyclic one-to-many transmission and multiple-to-receive mode is implemented by a microcontroller cyclically controlling the RF chip's transmission and reception. In a single cycle, one transmitting element can transmit a signal and M receiving elements can receive the echo signal. Therefore, collecting the complete NQ channel signals requires transmission from the same transmitting element. Secondary radar signals, among which This represents the floor function operator. The microcontroller switches and controls the transmitting array elements, performing NP data acquisition cycles to obtain the final NP×NQ radar echo signals. Each signal has N AD samples. r Taking a sixteen-chip, three-transmit, four-receiver configuration as an example, it is divided into four groups, each group containing four chips and twelve transmit antenna elements, resulting in the following chip grouping diagram: Figure 3 As shown. Chip number grouping is as follows. Figure 4 As shown. The chip transceiver process is designed as follows. Figure 5The transmission sequence is as follows: transmission elements are transmitted sequentially from group one to group four, and within each group, transmission follows the order shown in the table. Taking C1.Tx1 in transmission element group one as an example, with sixteen 3-transmit, 4-receive chips and a total of sixty-four receiving channels, C1.Tx1 needs to transmit four rounds of signals, with sixteen receiving channels receiving the echo signal in each transmission. After each group completes a full round of transmission and reception, a signal of size NP×NQ×N can be obtained. r The three-dimensional echo signal matrix.

[0058] 3. Signal processing module

[0059] In this embodiment, the signal processing module receives multi-channel echo signals and uses a hardware-parallel accelerated time-domain backpropagation (BP) algorithm for imaging. Specifically, the adaptation method of the U-shaped antenna array to the SAR imaging mechanism is to rapidly switch the simulated spatial motion of the transmitting antenna through electronic scanning to construct an equivalent synthetic aperture, and then process the echo signals received by the array using the SAR imaging algorithm to achieve three-dimensional high-resolution imaging.

[0060] A data acquisition scheme employing electronic scanning and cyclic one-to-many transmission is used. Before imaging the echo signal, the projection relationship is adjusted according to the spatial position between the target and the U-shaped antenna array. The acquired echo data is preprocessed to adapt to the subsequent time-domain backpropagation algorithm, specifically expressed as follows:

[0061] ;

[0062] in Represents the radar-acquired signal of a single target. This indicates slow time, specifically the time sequence of radar transmitted signals. Fast time refers to the time sequence of each radar signal propagation. and This indicates the position coordinates of the transmitting and receiving antennas. This indicates rearrangement of the echo signal. This represents the data rearrangement operator, which is used to determine the transmit antenna number and receive antenna number in the acquisition timing sequence according to the timing configuration of the cyclic one-to-many transmission mode, and fill the acquired signal into a three-dimensional matrix with the transmit antenna number as the row dimension, the receive signal number as the column dimension, and the AD sampling number as the third dimension.

[0063] Specifically, it is known that the final total number of NP×NQ×N rThe radar initially acquires a one-dimensional signal at each sampling point. During the data rearrangement stage, the signal processing module performs matrix reconstruction on the echo data. The specific mapping rule is as follows: the system treats the NQ received signals corresponding to each transmit antenna as a data vector. Based on the timing configuration of the cyclic transmit-receive mode, it determines the transmit antenna number and receive antenna number in the acquisition timing sequence, filling the target matrix with the transmit antenna number as the row index. Within this row vector, the spatial arrangement of each signal is determined by its receive antenna number. That is, the row dimension of the matrix corresponds to the transmit antenna number, and the column dimension corresponds to the receive signal number. The final result is a matrix of size NP×NQ×N. r A three-dimensional matrix.

[0064] Figure 1 The diagram above illustrates the simulation imaging algorithm flow of the time-domain backpropagation (BP) algorithm for echo signals from a U-shaped antenna array. In this embodiment, due to the use of a U-shaped sparse array suitable for near-field applications, the antenna geometry has been optimized, with the transmitting and receiving antennas positioned at opposite ends of the U-shape. Therefore, the original time-domain BP algorithm needs corresponding optimization, and a BP algorithm optimized based on the near-field transceiver split geometry is adopted. The first part is imaging preprocessing, which rearranges the echo data into a projection-ready form. Simultaneously, the imaging grid is divided by the imaging area and the grid resolution; among which... The remaining video phase compensation filter can be constructed as follows:

[0065] ;

[0066] in Indicates distance frequency, Indicates frequency modulation;

[0067] The second part describes 3D imaging using a time-domain backpropagation (BP) algorithm. The first step involves phase compensation of the focused signal, and the second step involves interpolation and accumulation of the coherent signals. The overall imaging process is represented as follows:

[0068] ;

[0069] in This represents the signal after data rearrangement and interpolation. The position coordinates are The sum of the distances from each grid point to the receiving and transmitting antennas is expressed as:

[0070] ;

[0071] and These are the position coordinates of the transmitting and receiving antennas, respectively; the phase compensation filter is represented as...

[0072] ;

[0073] in An exponential function with the natural constant as its base. represents an imaginary number, Here, c represents the carrier frequency, and c represents the speed of light. This represents the final image. , These represent the upper and lower limits of the y-coordinate of the receiving antenna, respectively. , These represent the upper and lower limits of the x-coordinate of the transmitting antenna, respectively. For a U-shaped antenna, the receiving antenna coordinates only change along the y-axis; the x-coordinate of the receiving antenna is not a variable and does not need to be accumulated. Similarly, there is no need to accumulate the y-coordinate of the transmitting antenna. During the imaging process, the echo signals received by each pair of transmitting and receiving antennas can be accumulated simultaneously using hardware acceleration for multiple slow-time sampling points. Theoretically, with sufficient hardware resources, the imaging time can approach the backward projection time of a single slow-time sampling point.

[0074] 4. Control Module

[0075] In this embodiment, the microcontroller in the control module is responsible for controlling the signal source and the FPGA chip, thereby controlling the sequence of signal transmission, signal acquisition and data storage of the entire system; the control signal of the RF chip is output by the microcontroller, and the four RF chips are grouped together; the microcontroller first transmits the control signal to the signal source, the signal source transmits the signal to the RF chip, then the microcontroller controls the RF chip to complete the transmission and reception process, and finally the microcontroller controls the FPGA chip to receive and store the ADC sampling signal.

[0076] Taking a three-transmitter, four-receiver chip as an example, a U-shaped near-field imaging radar system includes sixteen radio frequency (RF) chips. Two ADC chips are responsible for acquiring analog signals from the RF chips, and two FPGA chips are responsible for data conversion, facilitating the conversion of data returned by the ADC chips into a data format recognizable by the microcontroller. Sixteen differential quad-in-one multiplexers integrate the intermediate frequency (IF) signals, and another chip provides the LO (Local Receiver) signal. The microcontroller controls the entire chip's transmit and receive process. In this example, the refresh rate can reach 10Hz.

[0077] After determining the overall system architecture, the performance of individual antennas was simulated to verify their capabilities. The simulation results for the vertical and horizontal polarization gains of a single antenna are shown below. Figure 6 and Figure 7 As shown, by Figure 6 and Figure 7 It can be seen that a single antenna can meet the imaging requirements of the system.

[0078] The effectiveness of this invention can be further demonstrated through the following simulation experiments.

[0079] SAR Simulation Parameters and Results: Key simulation parameters are listed in Table 1. The three-dimensional coordinates of the nine target points are shown in Table 2. The two-dimensional azimuth and range coordinates of the central target point are 0, 0, and 0, respectively. To verify the system's imaging capability under antenna spacing greater than or equal to half a wavelength, the imaging results were obtained at antenna spacings of 0.5 times the wavelength, 0.75 times the wavelength, single wavelength, 1.25 times the wavelength, and 1.5 times the wavelength, as shown below. Figures 8-12 As shown in the simulation results, each imaging point is focused at the correct position, and the dB plot exhibits a standard two-dimensional sinc function shape, demonstrating the effectiveness of the proposed algorithm. Table 3 shows the three-dimensional resolution for each antenna spacing. Since the number of antennas is fixed, a larger antenna spacing results in a larger two-dimensional aperture and higher resolution. The table shows that this system can achieve three-dimensional high-resolution imaging tasks exceeding half a wavelength.

[0080] Table 1 Simulation parameters of the square-shaped radar SAR

[0081]

[0082] Table 2 Simulation point coordinates

[0083]

[0084] Table 3. 3D resolution of simulation points

[0085]

[0086] To highlight the three-dimensional imaging capability of this system, the stereo simulation experiment expanded the simulation points in Table 2 along the second-dimensional coordinate system twice, that is, the second-dimensional coordinate system was extended from... Change to and With other coordinates unchanged, a three-dimensional cube lattice is formed. Simulations are performed using the same parameters, and the results are as follows: Figure 13 As shown in the figure. Therefore, it can be seen that the optimized BP algorithm of this invention can complete the task of three-dimensional high-resolution imaging.

[0087] Any aspects of this invention not described in detail are well-known to those skilled in the art.

[0088] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A high spatiotemporal resolution millimeter-wave radar imaging system, characterized in that, include: The U-shaped antenna array module consists of a transmitting antenna array and a receiving antenna array, which are symmetrically distributed in a U-shape. The interval between the transmitting antenna elements and the receiving antenna elements is greater than or equal to half a wavelength, which is compatible with the SAR imaging mechanism and can achieve beam scanning in conjunction with the electronic scanning scheme. The radio frequency module adopts a cyclic one-transmit-multiple-receive mode. In each round of transmitting and receiving radio frequency signals, one transmitting array element transmits the signal and multiple receiving array elements receive the echo signal. Data acquisition of all transmitting and receiving channels is completed by cyclically switching the transmitting array element. The signal processing module is used to receive multi-channel echo signals, rearrange the echo signals, and perform imaging using a hardware-parallel accelerated time-domain BP algorithm. The control module uses a microcontroller to control the RF chip of the RF module.

2. The high spatiotemporal resolution millimeter-wave radar imaging system according to claim 1, characterized in that, In the U-shaped antenna array module, the transmitting antenna array consists of two parts: top and bottom, and left and right; the receiving antenna array consists of two parts: left and right, and top and bottom.

3. The high spatiotemporal resolution millimeter-wave radar imaging system according to claim 1, characterized in that, The radio frequency module includes N radio frequency chips, each of which integrates P transmit channels and Q receive channels; the N radio frequency chips together constitute NP transmit channels and NQ receive channels; the NQ analog signal echoes of the receive channels are uniformly digitally sampled by the AD sampling module.

4. The high spatiotemporal resolution millimeter-wave radar imaging system according to claim 3, characterized in that, The implementation of the cyclic one-transmit-multiple-receive mode is as follows: the microcontroller cyclically controls the RF chip to transmit and receive, and in one cycle, it controls one transmitting array element to transmit a signal and M receiving array elements to receive the echo signal. Collecting the complete NQ channel signal requires transmission from the same transmitter element. Secondary radar signals, among which This represents the rounding up operator; the microcontroller switches and controls the transmitting array elements, cyclically acquiring data NP times to obtain the final NP×NQ radar echo signals.

5. The high spatiotemporal resolution millimeter-wave radar imaging system according to claim 1, characterized in that, The adaptation method of the U-shaped antenna array to the SAR imaging mechanism is to simulate the spatial motion of the transmitting antenna by electronic scanning switching, construct an equivalent synthetic aperture, and process the echo signal received by the array using the SAR imaging algorithm to achieve three-dimensional imaging.

6. The high spatiotemporal resolution millimeter-wave radar imaging system according to claim 5, characterized in that, Before imaging the echo signal, the projection relationship is adjusted according to the spatial position between the target and the U-shaped antenna array. The acquired echo data is then preprocessed to adapt to the subsequent time-domain BP algorithm, specifically as follows: ； in Represents the radar-acquired signal of a single target. Indicates slow time. To save time, and This indicates the position coordinates of the transmitting and receiving antennas. This indicates rearrangement of the echo signal. This represents the data rearrangement operator, which is used to determine the transmit antenna number and receive antenna number in the acquisition timing sequence according to the timing configuration of the cyclic one-to-many transmission mode, and fill the acquired signal into a three-dimensional matrix with the transmit antenna number as the row dimension, the receive signal number as the column dimension, and the AD sampling number as the third dimension.

7. The high spatiotemporal resolution millimeter-wave radar imaging system according to claim 6, characterized in that, Three-dimensional imaging is performed using a time-domain backpropagation (BP) algorithm. The first step is to perform phase compensation on the focused signal, and the second step is to interpolate and accumulate the coherent signals. The overall imaging process is represented as follows: ； in This represents the signal after data rearrangement and interpolation. The position coordinates are The sum of the distances from each grid point to the receiving and transmitting antennas is expressed as: ； and These are the position coordinates of the transmitting and receiving antennas, respectively; the phase compensation filter is represented as... ； in An exponential function with the natural constant as its base. represents an imaginary number, Here, c represents the carrier frequency, and c represents the speed of light. This represents the final image. , These represent the upper and lower limits of the y-coordinate of the receiving antenna, respectively. , These represent the upper and lower limits of the x-coordinate of the transmitting antenna, respectively.

8. The high spatiotemporal resolution millimeter-wave radar imaging system according to claim 7, characterized in that, During the imaging process, the accumulation of data for each transmitting and receiving antenna is performed in parallel, using hardware acceleration to accumulate multiple slow-time sampling points simultaneously.

9. The high spatiotemporal resolution millimeter-wave radar imaging system according to claim 1, characterized in that, In each round of transmission and reception of the radar imaging system, the signal source first generates a local oscillator signal to the radio frequency chip. After receiving the local oscillator signal, the radio frequency chip transmits a millimeter-wave signal. After receiving the echo signal, the radio frequency chip receives the echo signal and the ADC chip samples it. After data sampling, the data is transmitted to the FPGA chip. The FPGA chip converts the sampled echo signal and transmits it to the signal processing module for data storage.

10. The high spatiotemporal resolution millimeter-wave radar imaging system according to claim 9, characterized in that, In the control module, the microcontroller is responsible for controlling the signal source and the FPGA chip, thereby controlling the sequence of signal transmission, signal acquisition and data storage of the entire system; the control signal of the RF chip is output by the microcontroller, and the four RF chips are grouped together; the microcontroller first transmits the control signal to the signal source, the signal source transmits the signal to the RF chip, then the microcontroller controls the RF chip to complete the transmission and reception process, and finally the microcontroller controls the FPGA chip to receive the ADC sampling signal and transfer it.

Images