A downward-looking three-dimensional ground imaging radar system and method

Abstract

The present application provides a downward-looking three-dimensional terrain imaging radar system, comprising: an array antenna, a radio frequency and beam control device, a signal processing device, and an integrated display and control device; the signal processing device generates a chirp pulse signal, the radio frequency and beam control device performs digital-to-analog conversion, filtering, phase shifting, and amplification on the signal, the array antenna performs beam synthesis on it, generates a radar signal and transmits it to the target scene; the array antenna is further used to receive the radar echo signal returned from the target scene, the radio frequency and beam control device performs filtering, amplification, phase shifting, and beam synthesis on the radar echo signal, the signal processing device performs analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing on it, and generates a three-dimensional topographic map directly below the flight platform; the present application generates a three-dimensional topographic map directly below the radar through real aperture super-resolution processing of the radar echo signal.

Description

Technical Field

[0001] This application relates to the field of radar, and in particular to a downward-looking three-dimensional terrain imaging radar system. Background Art

[0002] Currently, airborne radar high-resolution imaging technology has been widely applied in fields such as topographic mapping, terrain matching, material airdrop, and flight safety. This technology usually achieves high resolution in the range direction through pulse compression technology, high resolution in the azimuth direction through synthetic aperture technology (SAR), and obtains elevation information through interferometric processing (InSAR), thereby achieving three-dimensional high-resolution imaging.

[0003] The high-resolution imaging airborne radar based on SAR must operate in a side-looking or squint mode. Since the range direction of the SAR image actually shows the distance from the target to the radar, in areas with complex terrain such as mountains and cities, the distances from different scattering points to the radar may be the same. Therefore, their scattered echoes will fall into the same range cell of the radar system, forming aliasing, which is called layover. When the slope of the observation area is relatively large, higher terrain will block the backslope area. As Figure 1 shown, at this time, the radar cannot receive the scattered signals in this area, and the signal echoes in this area are manifested as thermal noise or speckle noise, which is called shadow. For layover and shadow areas, due to incorrect phase information, correct filtering and phase unwrapping cannot be performed. Not only can the elevation information of this area not be correctly estimated, but it will also affect the elevation estimation of adjacent normal areas, resulting in inevitable geometric distortion and shadow effects in the imaging result, affecting the imaging quality. At the same time, the existing SAR imaging technology cannot achieve high-resolution imaging of the area directly below the platform, which also greatly limits its applications in fields such as radar-assisted guidance, terrain matching, automatic landing, remote sensing, and anti-collision mechanisms. Summary of the Invention

[0004] In view of the above problems, this application provides a downward-looking three-dimensional terrain imaging radar system, which generates a three-dimensional topographic map directly below the radar by performing pulse compression, real-aperture super-resolution, and interferometric processing on the radar echo signal.

[0005] This application provides a downward-looking three-dimensional terrain imaging radar system, including: an array antenna, a radio frequency and beam control device, a signal processing device, and a comprehensive display and control device;

[0006] The signal processing device is used to generate a linear frequency modulation pulse signal and transmit the linear frequency modulation pulse signal to the radio frequency and beam control device;

[0007] The radio frequency and beam control device is used to perform digital-to-analog conversion, filtering, phase shifting, and amplification on the linear frequency modulation pulse signal, and transmit the linear frequency modulation pulse signal after digital-to-analog conversion, filtering, phase shifting, and amplification to the array antenna;

[0008] The array antenna includes a plurality of array elements; the plurality of array elements are used to perform beam synthesis on the chirp pulse signals after digital-to-analog conversion, filtering, phase shifting, and amplification, generate radar signals, and transmit them to the target scene. Among them, the radar signals include multiple beams, and the pointing directions of the multiple beams include directly below the radar system; the array antenna is also used to receive the radar echo signals returned from the target scene and transmit the radar echo signals to the RF and beam control device;

[0009] Among them, both the radar signals and the radar echo signals include 25 beam pointings;

[0010] The numbers of the 25 beam pointings are -12, -11, ……, -1, 0, 1, ……, 11, 12. The 25 beam pointings are divided into 5 segments, which are respectively:

[0011] The first segment: -12, -11, -10, -9;

[0012] The second segment: -8, -7, -6, -5, -4;

[0013] The third segment: -3, -2, -1, 0, 1, 2, 3;

[0014] The fourth segment: 4, 5, 6, 7, 8;

[0015] The fifth segment: 9, 10, 11, 12;

[0016] The beam pointings of the third segment are in the directly downward viewing direction of the flight platform;

[0017] The RF and beam control device is also used to perform filtering, amplification, phase shifting, and beam synthesis processing on the radar echo signals, and transmit the radar echo signals after filtering, amplification, phase shifting, and beam synthesis to the signal processing device;

[0018] The signal processing device is also used to perform analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing on the radar echo signals sent by the RF and beam control device, generate a three-dimensional topographic map of the directly downward view of the flight platform, and transmit the three-dimensional topographic map of the directly downward view of the flight platform to the integrated display and control device;

[0019] Among them, the processing sequence of the signal processing device for the 5 segments of the echo signals is as follows:

[0020] The signal processing device performs analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing on the beam of the third segment, and then sequentially performs analog-to-digital conversion, pulse compression, synthetic aperture, and interference processing on the beams of the second segment, the fourth segment, the fifth segment, and the first segment, so as to generate all three-dimensional topographic maps of the radar signals reaching the target scene;

[0021] The integrated display and control device is used to display the three-dimensional topographic map directly below the flight platform.

[0022] In one example, the array antenna includes array antenna A and array antenna B;

[0023] In a possible implementation, the array elements of array antenna A are used to perform beam synthesis on the chirp pulse signal after digital-to-analog conversion, filtering, phase shifting, and amplification, generate a radar signal, and transmit it to the target scene;

[0024] Array antenna A and array antenna B are also used to receive the radar echo signal returned from the target scene and transmit the radar echo signal to the RF and beam control device;

[0025] In a possible implementation, both array antenna A and array antenna B are 2×32 array antennas, located on both sides of the fuselage respectively, and the array surfaces of array antenna A and array antenna B face directly downward, with the long axis perpendicular to the flight path direction.

[0026] In one example, the RF and beam control device is multiple SOC RF chips.

[0027] In one example, the frequency of the chirp pulse signal is 12 GHz, the wavelength is 0.025 m, the bandwidth is 100 MHz, the pulse width is 1 μs, the PRF is 12195 Hz, the PRI is 82 μs, and the range resolution after pulse compression is 1.5 m.

[0028] In one example, the specific application of the signal processing device for processing the third beam of the radar echo signal sent by the RF and beam control device:

[0029] The signal processing device performs analog-to-digital conversion on the radar echo signal sent by the RF and beam control device, processes the radar echo signal after analog-to-digital conversion through pulse compression technology to generate range-direction high-resolution data; processes the range-direction high-resolution data through real-aperture super-resolution technology to generate high-resolution imaging in the vertical flight path direction directly below the fuselage; processes the range-direction high-resolution data through synthetic aperture technology to generate high-resolution imaging in the flight path direction; processes the high-resolution imaging in the vertical flight path direction and the high-resolution imaging in the flight path direction through interferometry processing to generate elevation information; the signal processing device is also used to register and synthesize the high-resolution imaging in the vertical flight path direction, the high-resolution imaging in the flight path direction, and the elevation information to generate a three-dimensional topographic map directly below.

[0030] In one example, the signal processing device is also specifically used for:

[0031] Perform analog-to-digital conversion on the second, fourth, fifth, and first beams of the radar echo signal sent by the RF and beam control device;

[0032] Process the second, fourth, fifth, and first beam segments after analog-to-digital conversion through pulse compression technology to generate range-direction high-resolution data;

[0033] Process the range-direction high-resolution data through synthetic aperture technology to generate cross-track high-resolution imaging;

[0034] Process the cross-track high-resolution imaging through interferometric processing technology to generate elevation information;

[0035] Register and synthesize the high-resolution imaging in the direction perpendicular to the flight track, cross-track high-resolution imaging, and elevation information corresponding to the third beam segment, as well as the cross-track high-resolution imaging and elevation information corresponding to the second, fourth, fifth, and first beam segments to generate a three-dimensional topographic map directly below the flight platform.

[0036] This application also provides an imaging method for generating a three-dimensional terrain directly below, including:

[0037] S1: Perform digital-to-analog conversion, filtering, phase shifting, and amplification on the generated chirp pulse signal;

[0038] S2; Perform beam synthesis on the chirp pulse signal that has undergone digital-to-analog conversion, filtering, phase shifting, and amplification to generate a radar signal and transmit it to the target scene; The radar signal includes multiple beam segments, and the pointing directions of the beam segments include directly below the radar system;

[0039] S3: Receive the radar echo signal returned from the target area and perform filtering, amplification, phase shifting, and beam synthesis on the radar echo signal;

[0040] S4: Perform analog-to-digital transformation, pulse compression, synthetic aperture, real aperture super-resolution, and interferometric processing on the radar echo signal that has undergone filtering, amplification, phase shifting, and beam synthesis;

[0041] S5: Generate a three-dimensional topographic map directly below the flight platform based on the data that has undergone analog-to-digital transformation, pulse compression, synthetic aperture, real aperture super-resolution, and interferometric processing.

[0042] Among them, both the radar signal and the radar echo signal include 25 beam pointings;

[0043] Both the radar signal and the radar echo signal include 25 beam pointings; The numbers of the 25 beam pointings are -12, -11, ……, -1, 0, 1, ……, 11, 12, and the 25 beam pointings are divided into 5 segments, which are respectively:

[0044] The first segment: -12, -11, -10, -9;

[0045] The second segment: -8, -7, -6, -5, -4;

[0046] Paragraph 3: -3, -2, -1, 0, 1, 2, 3;

[0047] Paragraph 4: 4, 5, 6, 7, 8;

[0048] Paragraph 5: 9, 10, 11, 12;

[0049] Among them, the beam direction of Paragraph 3 is the directly downward viewing direction of the flight platform;

[0050] Perform analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing on the beam of Paragraph 3, and then perform analog-to-digital conversion, pulse compression, synthetic aperture, and interference processing on the beams of Paragraph 2, Paragraph 4, Paragraph 5, and Paragraph 1 in sequence to generate all three-dimensional topographic maps of the radar signal reaching the target scene.

[0051] In an example, the specific order of processing the beam of Paragraph 3 is as follows:

[0052] Perform analog-to-digital transformation on the beam of Paragraph 3 of the radar echo signal that has been filtered, amplified, phase-shifted, and beam-combined;

[0053] Process the beam of Paragraph 3 after analog-to-digital conversion through pulse compression technology to generate range-direction high-resolution data;

[0054] Process the range-direction high-resolution data through real aperture super-resolution technology to generate high-resolution imaging in the direction perpendicular to the flight path;

[0055] Process the range-direction high-resolution data through synthetic aperture technology to generate high-resolution imaging in the flight path direction;

[0056] Process the high-resolution imaging in the direction perpendicular to the flight path and the high-resolution imaging in the flight path direction through interference processing technology to generate elevation information;

[0057] After registering and synthesizing the high-resolution imaging in the direction perpendicular to the flight path, the high-resolution imaging in the flight path direction, and the elevation information, generate a directly downward three-dimensional topographic map.

[0058] Advantages of this application:

[0059] 1. There are a total of 25 beams in the radar signal in this application. Among them, the beam of Paragraph 3 is used to detect the area directly below the array antenna A. Through the synthetic aperture, real aperture super-resolution, and interference processing of the beam of Paragraph 3 by the signal processing device, a three-dimensional topographic map of the directly downward view of the array antenna is obtained;

[0060] 2. There are a total of 2 array antennas in this application, adopting a one-transmit-two-receive mode, that is, the array antenna A is responsible for sending radar signals to the target scene, and the array antenna A and the array antenna B are used together to receive the radar echo signals returned from the target scene;

[0061] 3. This application performs analog-to-digital conversion, pulse compression, real-aperture super-resolution, and interference processing on radar echo signals, thereby avoiding layover and shadow in the imaging results. Brief Description of the Drawings

[0062] Figure 1 It is a schematic diagram of the SAR occlusion effect;

[0063] Figure 2 It is a block diagram of the composition of the radar system of this application;

[0064] Figure 3 It is a schematic diagram of the installation position of the array antenna of the radar system of this application;

[0065] Figure 4 It is a schematic diagram of the imaging principle of the radar system of this application;

[0066] Figure 5 It is a design block diagram of the SOC radio frequency chip in the radar system of this application;

[0067] Figure 6 It is a schematic diagram of the beam scanning in the vertical flight path direction of the radar system of this application;

[0068] Figure 7 It is a signal processing flow chart of the radar echo signal in the radar system of this application;

[0069] Figure 8 It is a connection block diagram of the radar system of this application. Detailed Embodiments

[0070] To make the objectives, technical solutions, and advantages of this application clearer, the following will combine the appended drawings in this application Figure 1-7 , and clearly and completely describe the technical solutions in this application. Obviously, the described embodiments are part of the embodiments of this application, rather than all of them. Based on the embodiments in this application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of this application.

[0071] Embodiment 1

[0072] As Figure 8 shown, this application provides a nadir three-dimensional imaging radar system, including: an array antenna, a radio frequency and beam control device, a signal processing device, and a comprehensive display and control device;

[0073] The signal processing device is used to generate a linear frequency modulation pulse signal and transmit the linear frequency modulation pulse signal to the radio frequency and beam control device;

[0074] A radio frequency and beam control device is used to perform digital-to-analog conversion, filtering, phase shifting, and amplification on a chirp pulse signal, and transmit the chirp pulse signal after digital-to-analog conversion, filtering, phase shifting, and amplification to an array antenna;

[0075] The array antenna includes a plurality of array elements; the plurality of array elements are used to perform beam synthesis on the chirp pulse signal after digital-to-analog conversion, filtering, phase shifting, and amplification, generate a radar signal and transmit it to a target scene. Among them, the radar signal includes a plurality of beams, and the pointing directions of the plurality of beams include directly below the radar system; the array antenna is also used to receive the radar echo signal returned from the target scene and transmit the radar echo signal to the radio frequency and beam control device;

[0076] The radio frequency and beam control device is also used to perform filtering, amplification, phase shifting, and beam synthesis processing on the radar echo signal, and transmit the radar echo signal after filtering, amplification, phase shifting, and beam synthesis to the signal processing device;

[0077] The signal processing device is also used to perform analog-to-digital conversion on the radar echo signal sent by the radio frequency and beam control device, process the radar echo signal after analog-to-digital conversion through pulse compression technology to generate high-resolution data in the range direction; process the high-resolution data in the range direction through real-aperture super-resolution technology to generate high-resolution imaging in the vertical flight path direction directly below the fuselage; process the high-resolution data in the range direction through synthetic aperture technology to generate high-resolution imaging in the flight path direction; process the high-resolution imaging in the vertical flight path direction and the high-resolution imaging in the flight path direction through interference processing technology to generate elevation information; register and synthesize the high-resolution imaging in the vertical flight path direction, the high-resolution imaging in the flight path direction, and the elevation information into a three-dimensional topographic map of the area directly below the flight platform, and transmit the three-dimensional topographic map of the area directly below the flight platform to the integrated display and control device;

[0078] The integrated display and control device is used to display the three-dimensional topographic map of the area directly below the flight platform.

[0079] In an embodiment of the present application, as Figure 3 shown, the array elements of array antenna A are used to perform beam synthesis on the chirp pulse signal after digital-to-analog conversion, filtering, phase shifting, and amplification, generate a radar signal and transmit it to a target scene;

[0080] Array antenna A and array antenna B are also used to receive the radar echo signal returned from the target scene and transmit the radar echo signal to the radio frequency and beam control device;

[0081] In a possible implementation manner, both array antenna A and array antenna B can be 2×32 array antennas, which are respectively located on both sides of the fuselage, and the array faces of array antenna A and array antenna B face directly downward, the long axis is perpendicular to the flight path direction, and they operate at 12 GHz;

[0082] In an alternative embodiment, as Figure 4 shown, during operation, the normal direction of the wide beam of the flight path always points to the directly downward viewing direction, and the narrow beam in the direction perpendicular to the flight path scans ±30° periodically; the element spacing in the direction perpendicular to the flight path and in the flight path direction of the antenna is both 16.5 mm, approximately equal to 2λ / 3, and the antenna size is 52.8 cm × 3 cm. The beam width in the direction perpendicular to the flight path of the antenna is 2.4°, and the beam width in the flight path direction is 42.5°;

[0083] In an alternative embodiment, at an altitude of 1500 m, the signal processing device receives the radar echo signal sent by the radio frequency and beam control device;

[0084] Among them, after the radar echo signal undergoes analog-to-digital conversion and pulse compression, the data of the range resolution can be obtained, and the range resolution is 1.5 m. The data of the range resolution is processed through synthetic aperture technology to obtain high-resolution imaging in the flight path direction, and the resolution in the flight path direction can reach 10 m. The data of the high resolution in the range direction is processed through real aperture super-resolution technology to obtain high-resolution imaging in the direction perpendicular to the flight path. The interferometric measurement technology is used to process the high-resolution imaging in the flight path direction and the high-resolution imaging in the direction perpendicular to the flight path to obtain the altitude value; among them, when the beam direction of the radar echo signal is within ±8.6°, the real aperture super-resolution technology is used to obtain high-resolution imaging in the direction perpendicular to the flight path, and the resolution is 6.6 m; when the beam direction of the radar echo signal is outside ±8.6°, the pulse compression technology can be used to obtain high-resolution imaging in the flight path direction, and the resolution is 10 m.

[0085] In the embodiment of the present application, the radio frequency and beam control device can be multiple Figure 5 general reconfigurable radio frequency SOC chips as

[0086] In an alternative embodiment, as Figure 5 shown, one receiving channel, one transmitting channel, and an on-chip digital calibration algorithm module, a high-speed digital control interface, a power management module, and a system status monitoring module are integrated in the SOC radio frequency chip;

[0087] In an alternative embodiment, the chip selects the SiGeBiCMOS process that meets high performance and high integration to ensure the integration of the system. The single chip has functions of amplification, filtering, phase shift, frequency conversion, and transceiver path;

[0088] In an alternative embodiment, the chip adopts the 0.13um SiGe BiCMOS process, so that the fT frequency of the device can reach more than 200 GHz, and the above chip combines an advanced circuit structure inside to ensure that the chip can be used at a working frequency of 4 GHz to 12 GHz. A sample-and-hold circuit is implemented in the SOC radio frequency chip to ensure direct radio frequency sampling at 4 GHz to 12 GHz;

[0089] In an alternative embodiment, the chip uses a low-noise amplifier with noise cancellation technology to reduce the impact of thermal noise and ensure the noise figure index. Through two-stage VGA adjustment, the first-stage VGA adjusts by 20 dB, the second-stage VGA adjusts by 40 dB, and the gain dynamic adjustment range is 60 dB;

[0090] In an alternative embodiment, the chip uses 24-bit sigma-delta fractional-N phase-locked loop technology to ensure the tuning resolution of the local oscillator frequency at the Hz level and meet the working frequency adjustment accuracy of 1 MHz; The chip adopts an on-chip tunable filter structure with a GM-C structure, and adjusts the filter frequency point and bandwidth by adjusting the transconductance value of the GM unit, and combines with the digital-domain filter to ensure this index; The chip integrates broadband phase shift implemented in a true-delay manner, ensuring a 360° phase adjustment range within the working frequency of 4G to 12G;

[0091] In an alternative embodiment, the chip meets sub-microsecond-level frequency point switching by adopting a radio frequency band-pass direct sampling receiver architecture and a sampling clock generation method of a DDS doubler, and combines with a QSPI control bus interface to achieve high-speed instruction issuance.

[0092] In the embodiments of the present application, the frequency of the linear frequency modulation pulse signal can be 12 GHz, the wavelength can be 0.025 m, the bandwidth can be 100 MHz, the pulse width can be 1 us, the pulse repetition frequency (PRF) can be 12195 Hz, the pulse repetition interval (PRI) can be 82 us, and the range resolution after pulse compression can be 1.5 m.

[0093] In this embodiment, as Figure 6 shown, both the radar signal and the radar echo signal include the same 25 beam directions; The radar signal includes 25 narrow beams, and each narrow beam can scan a range of 2.4° below the fuselage in the vertical direction of the flight path. The 25 narrow beams can scan a range of ±30° directly below the fuselage;

[0094] The numbers of the 25 beam directions are -12, -11, ……, -1, 0, 1, ……, 11, 12. The 25 beam directions are divided into 5 segments, which are respectively:

[0095] The 1st segment: -12, -11, -10, -9;

[0096] The 2nd segment: -8, -7, -6, -5, -4;

[0097] The 3rd segment: -3, -2, -1, 0, 1, 2, 3;

[0098] The 4th segment: 4, 5, 6, 7, 8;

[0099] Paragraph 5: 9, 10, 11, 12;

[0100] As Figure 7 shown, the beam direction of the third paragraph is the directly downward viewing direction of the flight platform. The signal processing device processes the echo signals of the five beams in the following order:

[0101] The signal processing device performs synthetic aperture, real aperture super-resolution, and interference processing on the third paragraph beam, and then sequentially performs synthetic aperture and interference processing on the second, fourth, fifth, and first paragraph beams, thereby generating all three-dimensional topographic maps of the radar signal reaching the target scene.

[0102] In the embodiment of the present application, the specific application of the signal processing device for processing the third paragraph beam in the radar echo signal sent by the radio frequency and beam control device:

[0103] The signal processing device performs analog-to-digital conversion on the radar echo signal sent by the radio frequency and beam control device, processes the radar echo signal after analog-to-digital conversion through pulse compression technology to generate high-resolution data in the range direction; processes the high-resolution data in the range direction through real aperture super-resolution technology to generate high-resolution imaging in the vertical flight path direction directly below the fuselage; processes the high-resolution data in the range direction through synthetic aperture technology to generate high-resolution imaging in the flight path direction; processes the high-resolution imaging in the vertical flight path direction and the high-resolution imaging in the flight path direction through interference processing technology to generate elevation information; the signal processing device is also used to register and synthesize the high-resolution imaging in the vertical flight path direction, the high-resolution imaging in the flight path direction, and the elevation information to generate a directly downward viewing three-dimensional topographic map.

[0104] In an alternative embodiment, the signal processing device is further specifically used for:

[0105] Perform analog-to-digital conversion on the second, fourth, fifth, and first paragraph beams of the radar echo signal sent by the radio frequency and beam control device;

[0106] Process the four beams after analog-to-digital conversion through pulse compression technology to generate high-resolution data in the range direction;

[0107] Process the high-resolution data in the range direction through synthetic aperture technology to generate high-resolution imaging in the flight path direction;

[0108] Process the high-resolution imaging in the flight path direction through interference processing technology to generate elevation information;

[0109] Register and synthesize the high-resolution imaging in the vertical flight path direction, the high-resolution imaging in the flight path direction, and the elevation information corresponding to the third paragraph beam, and the high-resolution imaging in the flight path direction and the elevation information corresponding to the other four beams to generate a directly downward viewing three-dimensional topographic map of the flight platform.

[0110] Working principle of this application: This application generates a chirp signal through a signal processing device. After the radio frequency and beam control device performs digital-to-analog conversion, filtering, phase shifting, and amplification on the chirp signal, the array antenna A synthesizes the beam of the chirp signal and transmits the generated radar signal to the target scene;

[0111] The array antenna A and the array antenna B receive the radar echo signal returned from the target scene. The radio frequency and beam control device filters, amplifies, phase-shifts, and synthesizes the beam of the radar echo signal. The signal processing device performs analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing on the radar echo signal sent by the radio frequency and beam control device, and generates a three-dimensional topographic map of the area directly below the flight platform. Finally, the integrated display and control device displays the three-dimensional topographic map of the area directly below the flight platform.

[0112] Embodiment 2

[0113] As Figure 2 shown, the signal processing device controls the radio frequency and beam control device through the FPGA and DSP. At the same time, it generates a chirp signal through the DA and transmits it to the radio frequency and beam control device;

[0114] The radio frequency and beam control device has an n-channel two-dimensional synthesis network inside, that is, n SOC radio frequency chips. The SHA, true delay phase shifter, amplifier, and radio frequency filter inside the SOC radio frequency chip complete the digital-to-analog conversion, filtering, phase shifting, and amplification of the chirp signal, and send it to the array antenna A and the array antenna B through the transceiver switch;

[0115] The transceiver switch in the radio frequency and beam control device is also used to receive the radar echo signals of the array antenna A and the array antenna B, and complete the filtering, amplification, phase shifting, and beam synthesis of the radar echo signals through the SHA, true delay phase shifter, amplifier, and radio frequency filter in the SOC radio frequency chip, and send the radar echo signals after filtering, amplification, phase shifting, and beam synthesis to the signal processing device;

[0116] The analog-to-digital conversion (ADC), programmable logic gate array (FPGA), and digital signal processing (DSP) of the signal processing device are used to perform analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing on the radar echo signals after filtering, amplification, phase shifting, and beam synthesis, so as to generate a three-dimensional topographic map of the area directly below the flight platform.

[0117] In an optional implementation manner, the FPGA and DSP of the signal processing device are also used to control the clock distribution module, and the clock distribution module is also used to send the sampling clock to the DA, ADC, and SOC radio frequency chips; and receive the sampling clock sent by the SOC radio frequency chip.

[0118] As Figure 3 shown, the distance between the central positions of the array antenna A and the array antenna B is the interference processing baseline length L.

[0119] As Figure 5 shown, the SOC RF chip can be divided into 8 regions in total: RX channel, RX sampling clock generation, TX local oscillator generation, TX channel, on-chip digital calibration algorithm, high-speed resin control interface, power management, and system status monitoring;

[0120] RX channel, after the RF signal sent by the signal processing device is input, it is processed in the RX channel through a low-noise amplifier, RF VGR, filter bank, true delay line, sample-and-hold amplifier, and RF VGA, and then sent by the output driver. Among them, the data generated by the RX sampling clock generation will be output together with the RF signal in the sample-and-hold amplifier;

[0121] RX sampling clock generation, through the reference clock input of the signal processing device, and then through a phase-locked loop, VCO, DDS, and X4 to output the sampling clock, and send the sampling clock to the signal processing device;

[0122] TX local oscillator generation, after the reference clock is input, it passes through a phase-locked loop and quadrature VCO clock distribution, and then is sent to the TX channel through two paths;

[0123] TX channel, receiving the input of the baseband signal (i.e., the radar echo signal), the baseband signal enters the TX channel through path 1 and path 0. Both baseband signals pass through the filter bank. Among them, the baseband signal of path 1 receives the data sent by the TX local oscillator generation after passing through the baseband VGA; the baseband signal of path 0 receives the data sent by the TX local oscillator after passing through the urgent amplifier. The baseband signals of path 0 and path 1 are added together and then converted into an RF signal through an RF amplifier, true delay line, and PA, and sent to the signal processing device.

[0124] Embodiment 3,

[0125] This application also provides an imaging method for generating a directly downward three-dimensional terrain, including:

[0126] S1: Perform digital-to-analog conversion, filtering, phase shifting, and amplification on the generated chirp pulse signal;

[0127] S2; Perform beam synthesis on the chirp pulse signal that has undergone digital-to-analog conversion, filtering, phase shifting, and amplification to generate a radar signal, and transmit it to the target scene; the radar signal includes multiple beams, and the pointing direction of the beams includes directly below the radar system;

[0128] S3: Receive the radar echo signal returned from the target area, and perform filtering, amplification, phase shifting, and beam synthesis on the radar echo signal;

[0129] S4: Perform analog-to-digital conversion, pulse compression, synthetic aperture, real-aperture super-resolution, and interferometric processing on the radar echo signals that have been filtered, amplified, phase-shifted, and beam-combined.

[0130] S5: Generate a three-dimensional topographic map of the area directly below the flight platform based on the data that has undergone analog-to-digital conversion, pulse compression, synthetic aperture, real-aperture super-resolution, and interferometric processing.

[0131] In this embodiment, the pointing direction of the third segment of the beam is the direction directly below the flight platform. Both the radar signal and the radar echo signal include 25 beam pointing directions. The numbers of the 25 beam pointing directions are -12, -11, ……, -1, 0, 1, ……, 11, 12. The 25 beam pointing directions are divided into 5 segments, which are respectively:

[0132] The first segment: -12, -11, -10, -9;

[0133] The second segment: -8, -7, -6, -5, -4;

[0134] The third segment: -3, -2, -1, 0, 1, 2, 3;

[0135] The fourth segment: 4, 5, 6, 7, 8;

[0136] The fifth segment: 9, 10, 11, 12;

[0137] Among them, perform analog-to-digital conversion, pulse compression, synthetic aperture, real-aperture super-resolution, and interferometric processing on the third segment of the beam, and then sequentially perform analog-to-digital conversion, pulse compression, synthetic aperture, and interferometric processing on the second segment, the fourth segment, the fifth segment, and the first segment of the beam to generate all three-dimensional topographic maps of the radar signal reaching the target scene.

[0138] In the embodiment of this application, the specific sequence of processing the third segment of the beam is as follows:

[0139] Perform analog-to-digital conversion on the third segment of the radar echo signal that has been filtered, amplified, phase-shifted, and beam-combined.

[0140] Process the third segment of the beam after analog-to-digital conversion through pulse compression technology to generate range-direction high-resolution data.

[0141] Process the range-direction high-resolution data through real-aperture super-resolution technology to generate high-resolution imaging in the direction perpendicular to the flight path.

[0142] Process the range-direction high-resolution data through synthetic aperture technology to generate high-resolution imaging in the flight path direction.

[0143] Process the high-resolution imaging in the direction perpendicular to the flight path and the high-resolution imaging in the flight path direction through interferometric processing technology to generate elevation information.

[0144] After registering and synthesizing the high-resolution imaging in the vertical flight path direction, the high-resolution imaging in the flight path direction, and the elevation information, a nadir three-dimensional topographic map is generated.

[0145] In practical applications, the present application can be used on flight units such as airplanes and drones.

[0146] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, the present application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the scope of the claims of the present application.

Claims

1. A downward-looking three-dimensional ground imaging radar system, characterized in that, Comprising: An array antenna, a radio frequency and beam control device, a signal processing device, and an integrated display and control device; The signal processing device is configured to generate a chirp pulse signal and transmit the chirp pulse signal to the radio frequency and the beam control device; The radio frequency and beam control device is configured to perform digital-to-analog conversion, filtering, phase shifting, and amplification on the chirp pulse signal, and transmit the chirp pulse signal after digital-to-analog conversion, filtering, phase shifting, and amplification to the array antenna; The array antenna includes a plurality of array elements; The plurality of array elements are configured to perform beam synthesis on the chirp pulse signal after digital-to-analog conversion, filtering, phase shifting, and amplification, generate a radar signal and transmit it to a target scene, wherein the radar signal includes a plurality of beams, and the pointing directions of the plurality of beams include directly below the radar system; the array antenna is further configured to receive a radar echo signal returned from the target scene and transmit the radar echo signal to the radio frequency and beam control device; Wherein, both the radar signal and the radar echo signal include 25 beam pointings; The 25 beam pointings are numbered -12, -11, ……, -1, 0, 1, ……, 11, 12, and the 25 beam pointings are divided into 5 segments, which are respectively: The 1st segment: -12, -11, -10, -9; The 2nd segment: -8, -7, -6, -5, -4; The 3rd segment: -3, -2, -1, 0, 1, 2, 3; The 4th segment: 4, 5, 6, 7, 8; The 5th segment: 9, 10, 11, 12; The beam pointing of the 3rd segment is the directly downward viewing direction of the flying platform; The radio frequency and beam control device is further configured to perform filtering, amplification, phase shifting, and beam synthesis processing on the radar echo signal, and transmit the radar echo signal after filtering, amplification, phase shifting, and beam synthesis to the signal processing device; The signal processing device is further configured to perform analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing on the radar echo signal sent by the radio frequency and beam control device, generate a three-dimensional topographic map of the directly downward view of the flying platform, and transmit the three-dimensional topographic map of the directly downward view of the flying platform to the integrated display and control device; Wherein, the processing sequence of the signal processing device for the 5 segments of light beams of the echo signal is as follows: The signal processing device performs analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing on the beam of the 3rd segment, and then sequentially performs analog-to-digital conversion, pulse compression, synthetic aperture, and interference processing on the beams of the 2nd segment, 4th segment, 5th segment, and 1st segment, so as to generate all three-dimensional topographic maps of the radar signal reaching the target scene; The integrated display and control device is configured to display the three-dimensional topographic map of the directly downward view of the flying platform.

2. The radar system according to claim 1, characterized in that, The array antenna includes array antenna A and array antenna B; The array elements of the array antenna A are configured to perform beam synthesis on the chirp pulse signal after digital-to-analog conversion, filtering, phase shifting, and amplification, generate the radar signal and transmit it to the target scene; The array antenna A and the array antenna B are also used to receive the radar echo signal returned from the target scene and transmit the radar echo signal to the RF and beam control device; Both the array antenna A and the array antenna B are 2×32 array antennas, which are located on both sides of the fuselage respectively. The array antenna A and the array antenna B face directly downward, and the long axis is perpendicular to the flight path direction.

3. The radar system according to claim 1, characterized in that, The RF and beam control device is multiple SOC RF chips.

4. The radar system according to claim 1, wherein The frequency of the linear frequency modulation pulse signal is 12 GHz, the wavelength is 0.025 m, the bandwidth is 100 MHz, the pulse width is 1 μs, the PRF is 12195 Hz, the PRI is 82 μs, and the range resolution after pulse compression is 1.5 m.

5. The radar system according to claim 1, characterized in that, The signal processing device is specifically used for: Performing analog-to-digital conversion on the third beam of the radar echo signal sent by the RF and beam control device; Processing the third beam after analog-to-digital conversion through the pulse compression technology to generate high-resolution data in the range direction; Processing the high-resolution data in the range direction through the real aperture super-resolution technology to generate a high-resolution image in the direction perpendicular to the flight path; Processing the high-resolution data in the range direction through the synthetic aperture technology to generate a high-resolution image in the flight path direction; Processing the high-resolution image in the direction perpendicular to the flight path and the high-resolution image in the flight path direction through the interferometric processing technology to generate elevation information; After registering and synthesizing the high-resolution image in the direction perpendicular to the flight path, the high-resolution image in the flight path direction, and the elevation information, generating the directly downward three-dimensional topographic map.

6. The radar system according to claim 1 or 5, characterized in that, The signal processing device is also specifically used for: Performing analog-to-digital conversion on the second, fourth, fifth, and first beams of the radar echo signal sent by the RF and beam control device; Processing the second, fourth, fifth, and first beams after analog-to-digital conversion through the pulse compression technology to generate high-resolution data in the range direction; Processing the high-resolution data in the range direction through the synthetic aperture technology to generate a high-resolution image in the flight path direction; Processing the high-resolution image in the flight path direction through the interferometric processing technology to generate elevation information; After registering and synthesizing the high-resolution image in the direction perpendicular to the flight path, the high-resolution image in the flight path direction, and the elevation information corresponding to the third beam, and the high-resolution image in the flight path direction and the elevation information corresponding to the second, fourth, fifth, and first beams, generating the directly downward three-dimensional topographic map of the flight platform.

7. An imaging method for generating a directly downward-looking three-dimensional terrain, characterized in that, Including: S1: Performing digital-to-analog conversion, filtering, phase shifting, and amplification on the generated linear frequency modulation pulse signal; S2: Performing beam synthesis on the linear frequency modulation pulse signal after digital-to-analog conversion, filtering, phase shifting, and amplification to generate a radar signal and transmitting it to the target scene; the radar signal includes multiple beams, and the pointing direction of the beams includes directly below the radar system; S3: Receiving the radar echo signal returned from the target area and performing filtering, amplification, phase shifting, and beam synthesis on the radar echo signal; S4: Perform analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing on the radar echo signals that have been filtered, amplified, phase-shifted, and beam synthesized; S5: Generate a three-dimensional topographic map of the area directly below the flight platform based on the data that has undergone analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing; Among them, both the radar signals and the radar echo signals include 25 beam directions; The numbers of the 25 beam directions are -12, -11, ……, -1, 0, 1, ……, 11, 12. The 25 beam directions are divided into 5 segments, which are respectively: The 1st segment: -12, -11, -10, -9; The 2nd segment: -8, -7, -6, -5, -4; The 3rd segment: -3, -2, -1, 0, 1, 2, 3; The 4th segment: 4, 5, 6, 7, 8; The 5th segment: 9, 10, 11, 12; The beam direction of the 3rd segment is the direction directly below the flight platform. Perform analog-to-digital conversion, pulse compression, synthetic aperture, real aperture super-resolution, and interference processing on the beam of the 3rd segment, and then sequentially perform analog-to-digital conversion, pulse compression, synthetic aperture, and interference processing on the beams of the 2nd segment, 4th segment, 5th segment, and 1st segment to generate all three-dimensional topographic maps of the radar signals reaching the target scene.

8. The imaging method according to claim 7, wherein The specific order of processing the beam of the 3rd segment is: Perform analog-to-digital conversion on the beam of the 3rd segment of the radar echo signals that have been filtered, amplified, phase-shifted, and beam synthesized; Process the beam of the 3rd segment after analog-to-digital conversion through the pulse compression technology to generate high-resolution data in the range direction; Process the high-resolution data in the range direction through the real aperture super-resolution technology to generate high-resolution imaging in the direction perpendicular to the flight path; Process the high-resolution data in the range direction through the synthetic aperture technology to generate high-resolution imaging in the flight path direction; Process the high-resolution imaging in the direction perpendicular to the flight path and the high-resolution imaging in the flight path direction through the interference processing technology to generate elevation information; After registering and synthesizing the high-resolution imaging in the direction perpendicular to the flight path, the high-resolution imaging in the flight path direction, and the elevation information, generate the three-dimensional topographic map of the area directly below.

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