Millimeter wave linear array three-dimensional imaging radar system

Abstract

The invention provides a millimeter wave linear array three-dimensional imaging radar system. The millimeter wave linear array three-dimensional imaging radar system comprises a W-frequency-band transceiving antenna array, a W-frequency-band transceiving channel, a radar signal processor and a clock / local oscillation frequency source, the W-band transmit-receive antenna array is arranged by using an MIMO architecture and is connected to one side, facing a target, of the aerial carrier platform. According to the method, an MIMO architecture is adopted for arraying, and special processing such as period extraction is carried out on a sparse arraying method for the W frequency band. In addition, under the condition of the same number of antenna units in sparse array arrangement, the array size is increased, the system resolution is improved, and meanwhile the cost of a radar system is reduced; a system combining a downward-looking linear array technology and a downward-looking synthetic aperture radar technology is adopted, the resolution in the elevation direction is greatly improved, reliability is enhanced, long-distance, large-range and efficient continuous operation can be achieved, and an effective means is provided for mountain deformation and landslide monitoring, earthquake disaster damage evaluation, agriculture and forestry pest and disease monitoring and the like under atrocious weather conditions.

Description

Technical Field

[0001] This invention relates to the field of radar technology, and more specifically to a millimeter-wave linear array three-dimensional imaging radar system. Background Technology

[0002] The millimeter-wave linear array three-dimensional imaging radar system is a three-dimensional imaging system that can accurately obtain three-dimensional information about the ground and ground targets, and can work in all weather and all time.

[0003] To address the need for accurate emergency mapping of 3D geographic entities, there is an urgent need to solve the problem that traditional SAR can only acquire 2D images. In areas with steep terrain and complex environments, 3D targets will be severely aliased on 2D images, resulting in many targets being unclear, indistinguishable, and difficult to understand. This makes it impossible to form the ability to construct 3D environments and interpret targets in detail, thus failing to achieve the effect of accurate mapping of 3D geographic entities.

[0004] The main factor contributing to the low resolution of current millimeter-wave linear array 3D imaging radar systems is the antenna frequency band. However, with the increase in antenna frequency band, existing antennas are unable to meet the requirements for grating lobes.

[0005] Therefore, there is a need for a high-resolution, high-reliability, long-range, wide-area, and highly efficient continuous three-dimensional imaging radar system. Summary of the Invention

[0006] This invention addresses the resolution and reliability issues of three-dimensional imaging radar systems by providing a millimeter-wave linear array three-dimensional imaging radar system. It employs a combination of downward-looking linear array technology and downward-looking synthetic aperture radar technology, significantly improving elevation resolution and enhancing reliability. This system enables long-distance, wide-area, and highly efficient continuous operation, providing an effective means for monitoring mountain deformation and landslides under harsh weather conditions, assessing earthquake damage, and monitoring agricultural and forestry pests and diseases.

[0007] This invention provides a millimeter-wave linear array three-dimensional imaging radar system, comprising a W-band transceiver antenna array, a W-band transceiver channel, a radar signal processor, and a clock / local oscillator frequency source connected in sequence to the W-band transceiver channel; The W-band transceiver antenna array uses a MIMO architecture and is deployed on the target-facing side of the carrier platform; The radar signal generated by the radar signal processor is mixed and amplified by the W-band transceiver channel and then radiated to the ground through the transmitting front end of the W-band transceiver antenna array. The echo signal scattered by the ground target is received by the W-band receiving front end of the W-band transceiver antenna array, and then amplified and mixed by the W-band transceiver channel before being output to the radar signal processor for digital sampling and real-time signal processing. The acquired compressed three-dimensional image is then transmitted to the ground intelligence processing software for processing, while the raw data received by the radar is recorded for use by the ground playback system.

[0008] The millimeter-wave linear array three-dimensional imaging radar system described in this invention, as a preferred embodiment, includes a W-band transceiver antenna array comprising N W-band transmitting antenna subarrays and M W-band receiving antenna elements. The W-band transmit antenna subarrays are uniformly distributed with a spacing of Ln / N, where Ln is the total length of the W-band transmit antenna array. The W-band receiving antenna unit is divided into two W-band receiving antenna arrays, which are symmetrically distributed at both ends of the W-band transceiver antenna array. Each W-band receiving antenna array includes M / 2 W-band receiving antenna units.

[0009] In a preferred embodiment of the millimeter-wave linear array three-dimensional imaging radar system described in this invention, each W-band receiving antenna array includes an odd number of W-band receiving antenna subarrays and an even number of W-band receiving antenna subarrays. The odd number of W-band receiving antenna subarrays are W-band receiving antenna elements located at odd positions when uniformly distributed, and the even number of W-band receiving antenna subarrays are W-band receiving antenna elements located at even positions when uniformly distributed. In each W-band receiving antenna array, the even-numbered W-band receiving antenna subarrays are shifted to the right by Ln / N: ; Where R(2:2:M / 2) is the position when the receiving antennas are evenly distributed with a spacing of 2 W-band receiving antennas starting from the second W-band receiving antenna element, and R'(2:2:M / 2) is the position after R(2:2:M / 2) is shifted to the right.

[0010] In a preferred embodiment of the millimeter-wave linear array three-dimensional imaging radar system described in this invention, the W-band transmitting antenna subarray is composed of a single W-band transmitting antenna or a phased array antenna array; the beam pointing of the W-band transmitting antenna is controlled by controlling the phase and amplitude of each phased array element in the phased array antenna array. The W-band receiving antenna element can be a single W-band receiving antenna or a W-band receiving antenna array. The element spacing dx of the subarray in the W-band receiving antenna array is λ / 4. The number of units m ≤ L / N 2 / dx.

[0011] In a preferred embodiment of the millimeter-wave linear array three-dimensional imaging radar system described in this invention, when the millimeter-wave linear array three-dimensional imaging radar system is working, N1 W-band transmitting antenna subarrays simultaneously transmit W-band signals, where N1 takes a value from 1 to N, and N W-band receiving antenna elements simultaneously receive echo signals. The dimensions of the vertical track antenna are determined based on the relationship between beamwidth θ and antenna aperture λ / D, where D is the antenna aperture. ; Where h is the flight altitude of the millimeter-wave linear array three-dimensional imaging radar, and Wg is the swath width in the vertical track direction; the W-band transmitting antenna subarray can achieve a swath width of NN×Wg by scanning NN angles through the gimbal in the pitch direction. The size of the antenna along the flight path is determined by both the repetition rate and the radar's effective range. PRF≥2V / D tV ; Where PRF is the pulse repetition frequency, V is the velocity, and D is the pulse repetition frequency. tV The dimensions of the transmitting antenna in the direction of flight.

[0012] In a preferred embodiment of the millimeter-wave linear array three-dimensional imaging radar system described in this invention, the effective range R of the millimeter-wave linear array three-dimensional imaging radar system is: ; Among them, P t This represents the system's peak transmit power. Let G be the total duration of the transmitted pulse, G be the gain of the transmitting and receiving antennas, and λ be the operating wavelength. The target scattering coefficient, Where k is the range resolution, k is the Boltzmann constant, and T0 is the operating temperature of the millimeter-wave linear array 3D imaging radar system. F n Let L be the noise figure of the millimeter-wave linear array three-dimensional imaging radar system, and L be the attenuation of the millimeter-wave linear array three-dimensional imaging radar system. =M m / (N*PRF), where N is the number of W-band transmit antenna subarrays in the W-band transceiver antenna array, and M m The number of pulses participating in coherent accumulation.

[0013] In the millimeter-wave linear array three-dimensional imaging radar system described in this invention, as a preferred embodiment, the antenna in the W-band transceiver antenna array is a pyramidal horn antenna. The W-band transmitting antenna subarray and the W-band receiving antenna unit are reciprocal.

[0014] In a preferred embodiment of the millimeter-wave linear array three-dimensional imaging radar system described in this invention, the W-band transceiver channel includes N W-band transmit channels and M W-band receive channels. The W-band echo signals received by the M-channel W-band receiving antenna unit enter the M-channel W-band receiving channel respectively. Each signal is filtered by low-noise amplifier for image rejection and then down-converted to the X-band by a subharmonic mixer. The high local oscillator is multiplied to provide a point frequency high local oscillator frequency source. The X-band signal is then filtered and amplified by a second down-conversion module to obtain an intermediate frequency signal, which is output to the M-channel AD unit for digital processing. In the N-channel W-band transmission channel, after the DA generates a signal, it is first up-converted to the X-band and then up-converted to the W-band. In the X-band, it is first switched to two signals by an RF switch, and then switched by a W-band switch to generate two 1-to-N / 2-channel W-band paths. Finally, after multi-stage power amplification, the W-band transmission signal is obtained and output to the N-channel W-band transmission antenna subarray.

[0015] The millimeter-wave linear array three-dimensional imaging radar system of the present invention, in a preferred embodiment, includes an AD chip, a DA chip, at least two acquisition processing boards, and at least two data processing boards in the radar signal processor. The radar signal processor generates and acquires waveforms through AD and DA chips. The FPGA on the acquisition and processing board generates and controls the radar operating timing and controls internal and external communication. The FPGA on the data processing board performs digital signal preprocessing.

[0016] The millimeter-wave linear array three-dimensional imaging radar system of the present invention, in a preferred embodiment, further includes a servo control system, a POS positioning system, and a power supply module; The radar signal processor and POS positioning system are both connected to the servo control system. The W-band transceiver antenna array is connected to the carrier platform through the servo control system. The POS positioning system is an IMF inertial navigation system. On an aircraft's flight path, a millimeter-wave linear array 3D imaging radar can image a rectangular area at a time. The working process is as follows: when the aircraft is flying over the target, the W-band transceiver antenna array on the aircraft platform transmits millimeter-wave signals to illuminate the target. The W-band transceiver antenna array receives the millimeter-wave echoes and completes the 3D image acquisition through a 3D imaging algorithm. The spatial 3D coordinates of the target surface points are determined based on the MIMO array imaging in the vertical track direction, the altitude range image, and the azimuth synthetic aperture radar imaging, thus achieving 3D imaging. During signal processing, the echo signal is averaged every MM pulses before subsequent signal processing. The value of MM ranges from 1 to 128. At the same time, the repetition rate of the signal processing is reduced by MM times. The complexity of signal processing is reduced by increasing the aperture of the antenna in the flight direction.

[0017] The present invention has the following advantages: This invention employs a MIMO architecture for array deployment, and for the W-band, special processing such as periodic decimation is applied to the sparse array method. Furthermore, the sparse array increases the array size with the same number of antenna elements, improving system resolution while reducing radar system costs. The combination of downward-looking array technology and downward-looking synthetic aperture radar technology significantly improves elevation resolution and enhances reliability, enabling long-range, wide-area, and highly efficient continuous operation. This provides an effective means for monitoring mountain deformation and landslides under harsh weather conditions, assessing earthquake damage, and monitoring agricultural and forestry pests and diseases. Attached Figure Description

[0018] Figure 1 A block diagram of a millimeter-wave linear array three-dimensional imaging radar system; Figure 2 This is a diagram showing the positions of array antenna elements and equivalent antenna elements in a millimeter-wave linear array three-dimensional imaging radar system. Figure 3 This is the radiation pattern of a subarray antenna element in a millimeter-wave linear array three-dimensional imaging radar system. Figure 4a A simulation diagram of the MIMO cross-track directional resolution of a millimeter-wave linear array three-dimensional imaging radar system; Figure 4b This is a schematic diagram of the edge resolution of a millimeter-wave linear array three-dimensional imaging radar system. Figure 4c This is a schematic diagram of the intermediate resolution of a millimeter-wave linear array three-dimensional imaging radar system. Figure 5 A block diagram illustrating the transceiver channel principle of a millimeter-wave linear array three-dimensional imaging radar system; Figure 6 This is a schematic diagram of an antenna design for a millimeter-wave linear array three-dimensional imaging radar system.

[0019] Figure label: 1. W-band transceiver antenna array; 11. W-band transmit antenna subarray; 12. W-band receive antenna element; 121. Odd-numbered W-band receive antenna subarray; 122. Even-numbered W-band receive antenna subarray; 2. W-band transceiver channel; 21. W-band transmit channel; 22. W-band receive channel; 3. Radar signal processor; 4. Clock / local oscillator frequency source; 5. Servo control system; 6. POS positioning system. Detailed Implementation

[0020] 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

[0021] A millimeter-wave linear array three-dimensional imaging radar system addresses the challenge of antenna size reduction in the W-band due to its high carrier frequency and short wavelength. While W-band radar systems allow for smaller antennas, achieving half-wavelength dimensions with physical antenna elements presents difficulties in array deployment. This invention employs a MIMO architecture for array deployment, incorporating special processing techniques such as periodic decimation in the sparse array method for the W-band. Furthermore, the sparse array method increases the array size while maintaining the same number of antenna elements, improving system resolution and reducing radar system cost.

[0022] like Figure 1 As shown, the millimeter-wave linear array three-dimensional imaging radar system of the present invention mainly includes a W-band transceiver antenna array 1, a W-band transceiver channel 2, a radar signal processor 3, a clock / local oscillator frequency source 4, a servo control system 5, a POS positioning system, and a power supply module.

[0023] When the millimeter-wave linear array 3D imaging radar system is operating, the radar signal processor 3 generates a radar operating signal according to the received relevant parameters. After mixing in the W-band transceiver channel 2, the signal is sent to the transmitter for power amplification and then radiated to the ground through the W-band transmitting front end. The echo signal scattered by the ground target is received by the W-band receiving front end, amplified and mixed in the receiving channel, and then sent to the radar signal processor 3 for digital sampling and real-time signal processing. Finally, the acquired compressed 3D image is transmitted to the ground intelligence processing software through the image transmission module for processing. At the same time, the raw data received by the radar is recorded for use by the ground playback system.

[0024] On an aircraft's flight path, a millimeter-wave linear array 3D imaging radar can image a rectangular area at a time. Its basic operation is as follows: when the aircraft flies over the target, the MIMO array antenna transmission system on the aircraft platform emits millimeter-wave signals to illuminate the target. The MIMO array antenna receives the millimeter-wave echoes and uses 3D imaging algorithms to acquire a 3D image. The spatial 3D coordinates of points on the target surface are determined based on MIMO array imaging in the vertical flight path direction, altitude range image, and azimuth synthetic aperture radar imaging, thus achieving 3D imaging.

[0025] Antenna array design The W-band transceiver antenna array 1 in this scheme adopts a MIMO array design, where N is the number of W-band transmit antenna elements 11, the length of the W-band transmit antenna array is Ln, the W-band transmit antenna elements are evenly distributed with a spacing of Ln / N, and the number of W-band transmit antenna subarrays can be 1 to 48.

[0026] The number of W-band receiving antenna elements 12 is M. These elements are located at both ends of the array, forming two large arrays. Each large subarray consists of M / 2 smaller subarrays. The spacing between the M / 2 smaller subarrays is 2Ln / N / M. To increase the spacing and avoid array errors, the positions R(1:M) of the W-band receiving antenna elements (from element 1 to element M) can be taken at intervals, and Ln / N is added to these points. This means that even-numbered W-band receiving antenna subarrays 122 are shifted to the right by Ln / N, while odd-numbered W-band receiving antenna subarrays 121 remain unchanged. The specific formula is as follows: R'(2:2:M / 2)=R(2:2:M / 2)+Ln / N.

[0027] Where R(2:2:M) represents the rightward shift of the second W-band receiving antenna element by Ln / N, with an interval of 2 W-band receiving antenna elements, until all M W-band receiving antenna elements are present. This arrangement can significantly reduce the grating lobes of the W-band receiving antennas.

[0028] Each receiving element can consist of a single antenna or a small array antenna. If it is an array antenna, the element spacing dx of each subarray is λ / 4. The number of units m ≤ L / N 2 / dx.

[0029] Each W-band transmitting antenna element 11 can be composed of a single antenna or a phased array antenna array. If it is composed of a phased array antenna, the beam direction of the transmitting antenna can be controlled by controlling the phase and amplitude of each phased array element. Figure 2 This demonstrates a specific example of an array configuration, showing a configuration with 16 transmitting antenna elements (located in...). Figure 2 The lower part) and the number of receiving antenna elements is 16 (located in the lower part) Figure 2 The diagram showing the positions of the array antenna elements and the equivalent antenna element positions (located in the upper part) Figure 2 (Central section). In practice, the number of transmitting antenna elements can be any value from 1 to 48. The position of the transmitting antenna element is represented by TX, and the position of the receiving element is represented by RX. The equivalent antenna element position is (TX+RX) / 2, and the equivalent antenna element position is as follows: Figure 2 The image shows the midpoint between the transmitting and receiving antennas. The radiation pattern of the subarray elements is shown below. Figure 3 As shown. The equivalent antenna, arranged according to the above rules, yields antenna patterns ranging from -8° to 8°, with 1° intervals, as shown below. Figure 4a As shown. The resolution is 0.23 degrees when the scanning angle is 8 degrees. Figure 4b As shown, when the scanning angle is 0 degrees, the resolution is 0.12 degrees. Figure 4c As shown.

[0030] When a millimeter-wave linear array 3D imaging radar is operating, N1 W-band transmitting antenna elements transmit simultaneously, where N1 ranges from 1 to (N-1). N W-band receiving antenna subarrays receive simultaneously. The value of N1 depends on the radar's effective range. The size of the subarray is determined by the antenna beamwidth; a wider beamwidth results in a wider swath on the ground.

[0031] First, determine the flight altitude h and the required swath width Wg in the vertical track direction for a millimeter-wave linear array 3D imaging radar. Calculate the beamwidth based on the flight altitude and swath width; the formula for calculating the antenna element beamwidth θ is 2*arctan(Wg / 2h). Then, determine the relationship between beamwidth θ and antenna aperture λ / D, where D is the antenna aperture. This determines the dimensions of the vertical track 3D antenna. The antenna dimensions along the track direction are determined by the repetition frequency (RF) and the radar's effective range. PRF ≥ 2*V / D tV PRF is the pulse repetition frequency, V is the velocity, and D is the pulse repetition frequency. tV The dimensions of the transmitting antenna in the direction of flight.

[0032] The radar equation is shown below, P t This represents the system's peak transmit power. Let G be the total duration of the transmitted pulse, G be the gain of the transmitting and receiving antennas, and λ be the operating wavelength. It is the target scattering coefficient. Where is the distance resolution, k is the Boltzmann constant, T0 is the system operating temperature, Fn is the system noise figure, and L is the system attenuation. =M m / (N*PRF), where N is the number of transmit antenna elements, M m The number of pulses participating in coherent accumulation. N can be 1 to 48.

[0033] ; According to the antenna range formula, the higher the antenna gain, the greater the range; conversely, a higher antenna gain requires a larger antenna size D. tV The larger the value, the larger the antenna size, according to PRF>=2*V / D tV The lower the system repetition rate, the better. The system requires each transmitting unit to complete one transmission and one echo reception to complete a full data acquisition; therefore, the more transmitting antenna elements there are, the higher the repetition rate.

[0034] The size of the range antenna is determined by the range beamwidth; the larger the beamwidth, the smaller the antenna size is required.

[0035] ; Where h is the height of the flight platform. Let θ = λ / D be the beamwidth of the transmitting antenna in the elevation direction. To obtain a wider swath, the transmitting antenna can be scanned in the elevation direction by a gimbal, achieving a swath width of NN*Wg by scanning NN angles.

[0036] Antenna Unit Design The W-band front-end antenna can adopt various antenna design forms. This article takes the pyramidal horn design as an example, where the antenna element is divided into receiving and transmitting parts. This antenna easily achieves low sidelobe characteristics.

[0037] Based on the subsystem's requirements for low sidelobes and high gain antennas, a pyramidal horn antenna can be used for both transmitting and receiving to achieve the required single-channel beamwidth. The pyramidal horn antenna has the following shape... Figure 6 As shown.

[0038] W-band radar transceiver channel 2 like Figure 5 As shown, the W-band radar transceiver channel 2 is the core component of the W-band multi-function radar. It employs N W-band transmit channels 21 and M W-band transceiver channels 22, arranged in a MIMO array configuration. The main functions of the W-band transmit channel 21, W-band receive channel 22, and clock / local oscillator frequency source module 4 are as follows: 1) It is responsible for converting the S-band intermediate frequency signal generated by 1 DA to the X-band through two frequency conversions, and then splitting the signal into N W-band signals through the X-band and W-band switching and power amplification, and transmitting them through the transmitting antenna.

[0039] 2) Responsible for amplifying the echo signals received by the N W-band receiving antennas with low noise, and then downconverting them to N intermediate frequencies for digital processing by the N AD converters at the back end.

[0040] 3) Clock / Local Oscillator Frequency Source Module 4 generates high and low local oscillator signals to support multiple up and down conversions.

[0041] 4) Generate a clock signal to provide a clock for AD and DA.

[0042] After receiving the W-band signal, the W-band receiving antenna (M-channel) sends it to the M-channel W-band receiving channel 22. Each signal passes through a low-noise amplifier, is filtered by image rejection, and then down-converted to the X-band by a subharmonic mixer. The high-frequency local oscillator is multiplied to provide a point-frequency high-frequency source. The first intermediate frequency of the X-band is then down-converted to the second intermediate frequency by a second down-conversion module, filtered, amplified, and fed to the A / D converter (N-channel).

[0043] When the number of transmit channels is selected as N, for transmit channel 21 in the W band, the D / A converter generates one signal, which is converted to the W band after passing through the same secondary up-conversion as the receiving array. In the X band, it is first switched to two signals by the RF SPDT switch, and then switched by the W band SP8T switch to generate two 1-to-8 W band paths. Finally, the W band undergoes multi-stage power amplification to push each signal to 6W and send it to the transmit antenna (a total of N paths).

[0044] W-band radar signal processor 3 Based on the signal processor's functions, AD and DA chips need to be selected to generate and acquire waveforms. The FPGA acquisition and processing board generates and controls the radar's operating timing, as well as handles various internal and external communication controls. Furthermore, the FPGA data processing board implements digital signal preprocessing. According to the signal processor's design requirements and main functions, this design's signal processor consists of N / 2 acquisition and processing boards and 2 data processing boards, as shown in the block diagram below: The signal processor consists of an acquisition and processing board and a data processing board. The acquisition and processing board realizes AD acquisition, DA transmission, echo storage, radar working timing generation and control, and the data processing board realizes digital signal preprocessing and external communication.

[0045] Real-time digital signal processing is implemented in the signal processor to obtain a 3D point target image. The data is then transmitted to the ground display terminal via a data transmission module. During echo signal acquisition, when the number of transmitting units N is large, the repetition rate (RF) increases by a factor of N. To reduce the RF and improve the signal-to-noise ratio, the echo signal is averaged every M / M pulses before further processing. M / M can range from 1 to 128, with 32 being preferred. This reduces the RF by a factor of M / M, effectively increasing the aperture of the flight direction antenna and reducing the complexity of signal processing.

[0046] In this embodiment, the W-band transceiver antenna array 1 uses a lightweight material antenna with 16 receiving channels and is connected to a two-axis servo stabilization platform. This isolates aircraft attitude disturbances and controls the antenna beam pointing, enabling a downward-looking 3D imaging mode. The antenna employs a MIMO antenna array design with 16 transmitting and 16 receiving channels, connected to a three-axis servo stabilization platform. This isolates aircraft attitude disturbances and controls the antenna beam pointing, enabling a downward-looking 3D imaging mode. When the aircraft flies over the target, the MIMO array antenna transmitting system on the aircraft platform transmits millimeter-wave signals to illuminate the target. The MIMO array antenna receives the millimeter-wave echoes and focuses them onto the detector to acquire ranging and intensity images. The spatial 3D coordinates of points on the target surface are determined based on the transorbital MIMO array directional imaging, the altitude-dimensional range image, and the synthetic aperture radar imaging along the orbital direction, thus achieving 3D imaging. The radar signal processor 3 uses a single-board design to implement system control, signal generation, acquisition and processing, and data electrical interface with the aircraft. The transmitter uses a solid-state power amplifier, providing high reliability.

[0047] 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 linear array three-dimensional imaging radar system, characterized in that: It includes a W-band transceiver antenna array (1), a W-band transceiver channel (2), a radar signal processor (3), and a clock / local oscillator frequency source (4) connected in sequence to the W-band transceiver channel (2). The W-band transceiver antenna array (1) is deployed using a MIMO architecture and connected to the target-facing side of the carrier platform; The radar signal generated by the radar signal processor (3) is mixed and amplified by the W-band transceiver channel (2) and then radiated to the ground through the transmitting front end of the W-band transceiver antenna array (1). The echo signal scattered by the ground target is received by the W-band receiving front end of the W-band transceiver antenna array (1), and then amplified and mixed by the W-band transceiver channel (2) before being output to the radar signal processor (3) for digital sampling and real-time signal processing. The obtained compressed three-dimensional image is then transmitted to the ground intelligence processing software for processing, and the original data received by the radar is recorded for use by the ground playback system.

2. The millimeter-wave linear array three-dimensional imaging radar system according to claim 1, characterized in that: The W-band transceiver antenna array (1) includes N W-band transmit antenna subarrays (11) and M W-band receive antenna elements (12). The W-band transmitting antenna subarray (11) is uniformly distributed with a spacing of Ln / N, where Ln is the total length of the W-band transmitting antenna array; The W-band receiving antenna unit (12) is divided into two W-band receiving antenna arrays, which are symmetrically distributed at both ends of the W-band transceiver antenna array (1). Each W-band receiving antenna array includes M / 2 W-band receiving antenna units (12).

3. The millimeter-wave linear array three-dimensional imaging radar system according to claim 2, characterized in that: Each of the W-band receiving antenna arrays includes an odd number of W-band receiving antenna subarrays (121) and an even number of W-band receiving antenna subarrays (122). The odd number of W-band receiving antenna subarrays (121) are W-band receiving antenna elements located at odd positions when uniformly distributed, and the even number of W-band receiving antenna subarrays (122) are W-band receiving antenna elements located at even positions when uniformly distributed. Each of the even-numbered W-band receiving antenna subarrays (122) in the W-band receiving antenna array is shifted to the right by Ln / N: ； Where R(2:2:M / 2) is the position when the receiving antennas are evenly distributed with a spacing of 2 W-band receiving antennas starting from the second W-band receiving antenna element, and R'(2:2:M / 2) is the position after R(2:2:M / 2) is shifted to the right.

4. The millimeter-wave linear array three-dimensional imaging radar system according to claim 2, characterized in that: The W-band transmitting antenna subarray (11) is composed of a single W-band transmitting antenna or a phased array antenna array; the beam pointing of the W-band transmitting antenna is controlled by controlling the phase and amplitude of each phased array element in the phased array antenna array. The W-band receiving antenna element (12) is a single W-band receiving antenna or a W-band receiving antenna array, and the element spacing dx of the subarray in the W-band receiving antenna array is λ / 4~ The number of units m ≤ L / N 2 / dx.

5. A millimeter-wave linear array three-dimensional imaging radar system according to claim 2, characterized in that: When the millimeter-wave linear array three-dimensional imaging radar system is working, N1 of the W-band transmitting antenna subarrays (11) simultaneously transmit W-band signals, N1 takes the value of 1 to (N-1), and N of the W-band receiving antenna elements (12) simultaneously receive echo signals. The dimensions of the vertical track antenna are determined based on the relationship between beamwidth θ and antenna aperture λ / D, where D is the antenna aperture. ； Where h is the flight altitude of the millimeter-wave linear array three-dimensional imaging radar, and Wg is the swath width in the vertical track direction; the W-band transmitting antenna subarray (11) can achieve a swath width of NN×Wg by scanning NN angles through the gimbal in the pitch direction. The size of the antenna along the flight path is determined by both the repetition rate and the radar's effective range. PRF≥2V / D tV ; Where PRF is the pulse repetition frequency, V is the velocity, and D is the pulse repetition frequency. tV The dimensions of the transmitting antenna in the direction of flight.

6. The millimeter-wave linear array three-dimensional imaging radar system according to claim 1, characterized in that: The effective range R of the millimeter-wave linear array three-dimensional imaging radar system is: ； Among them, P t This represents the system's peak transmit power. Let G be the total duration of the transmitted pulse, G be the gain of the transmitting and receiving antennas, and λ be the operating wavelength. The target scattering coefficient, Where k is the range resolution, k is the Boltzmann constant, and T0 is the operating temperature of the millimeter-wave linear array 3D imaging radar system. F n Let L be the noise figure of the millimeter-wave linear array three-dimensional imaging radar system, and L be the attenuation of the millimeter-wave linear array three-dimensional imaging radar system. =M m / (N*PRF), where N is the number of W-band transmit antenna subarrays (11) in the W-band transceiver antenna array (1), and M m The number of pulses participating in coherent accumulation.

7. A millimeter-wave linear array three-dimensional imaging radar system according to claim 2, characterized in that: The antenna in the W-band transceiver antenna array (1) is a pyramidal horn antenna; The W-band transmitting antenna subarray (11) and the W-band receiving antenna unit (12) are reciprocal.

8. A millimeter-wave linear array three-dimensional imaging radar system according to claim 2, characterized in that: The W-band transceiver channel (2) includes N W-band transmit channels (21) and M W-band receive channels (22). The W-band echo signals received by the M-channel W-band receiving antenna unit (12) enter the M-channel W-band receiving channel (22). Each signal is filtered by a low-noise amplifier and then down-converted to the X-band by a subharmonic mixer. The high local oscillator is multiplied to provide a point-frequency high local oscillator frequency source. The X-band signal is then filtered and amplified by a second down-conversion module to obtain an intermediate frequency signal, which is then output to the M-channel AD unit for digital processing. In the N-way W-band transmission channel (21), after the DA generates a signal, it is first up-converted to the X-band and then up-converted to the W-band. In the X-band, it is first switched to two signals by an RF switch, and then switched by a W-band switch to generate two 1-to-N / 2 W-band paths. Finally, after multi-stage power amplification, the W-band transmission signal is obtained and output to the N-way W-band transmission antenna subarray (11).

9. A millimeter-wave linear array three-dimensional imaging radar system according to claim 1, characterized in that: The radar signal processor (3) includes an AD chip, a DA chip, at least two acquisition processing boards and at least two data processing boards; The radar signal processor (3) generates and acquires waveforms through AD and DA chips. The FPGA of the acquisition and processing board generates and controls the radar working timing and controls internal and external communication. The FPGA of the data processing board performs digital signal preprocessing.

10. A millimeter-wave linear array three-dimensional imaging radar system according to claim 1, characterized in that: It also includes a servo control system (5), a POS positioning system (6), and a power supply module; The radar signal processor (3) and the POS positioning system (6) are both connected to the servo control system (5). The W-band transceiver antenna array (1) is connected to the carrier platform through the servo control system (5). The POS positioning system (6) is an IMF inertial navigation system. On the aircraft's flight path, the millimeter-wave linear array three-dimensional imaging radar can image a rectangular area at a time. The working process is as follows: when the aircraft is flying over the target, the W-band transceiver antenna array (1) on the carrier platform transmits millimeter-wave signals to illuminate the target. The W-band transceiver antenna array (1) receives the millimeter-wave echo and completes the three-dimensional image acquisition through the three-dimensional imaging algorithm. The spatial three-dimensional coordinates of the target surface points are determined according to the vertical track direction MIMO array direction imaging, the height dimension range image and the azimuth direction synthetic aperture radar imaging to achieve three-dimensional imaging. During signal processing, the echo signal is averaged every MM pulses before subsequent signal processing. The value of MM ranges from 1 to 128. At the same time, the repetition rate of the signal processing is reduced by MM times. The complexity of signal processing is reduced by increasing the aperture of the antenna in the flight direction.

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