Close-range correction method for multiple-input-multiple-output ground-based synthetic aperture radar
By performing digital cancellation, bandwidth adjustment and coherent superposition on the radar echo data of the MIMO-GBSAR system, the problem of poor robustness in complex environments is solved, and high-precision system correction and imaging effects are achieved.
Patent Information
- Application Number
- CN202510644363.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-19
- Publication Date
- 2025-07-29
Smart Images
Figure CN120386009A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of radar signal processing and imaging technology, and particularly to a near-distance calibration method for a multiple-input multiple-output ground-based synthetic aperture radar. Background Art
[0002] The ground-based synthetic aperture radar technology has the advantages of all-weather, all-day, high spatial resolution, and sub-millimeter deformation monitoring, and has been widely used in many fields such as landslide monitoring, mine pit deformation measurement, and building structural health monitoring. The traditional SISO (Single-Input Single-Output) mechanical scanning GBSAR system has defects such as long scanning time and poor real-time performance, and it is difficult to meet the real-time monitoring requirements in fast dynamic scenarios. To overcome such deficiencies, the MIMO (Multiple-Input Multiple-Output)-GBSAR (Ground-Based Synthetic Aperture Radar) technology has emerged. MIMO-GBSAR transmits and receives signals through multiple channels simultaneously, significantly improving the real-time performance and robustness of the radar system, and becoming a current research hotspot.
[0003] However, in the actual application process of the MIMO-GBSAR system, it faces many technical challenges. Among them, the inconsistency of array channels seriously affects the imaging performance of the system, and the system error is further exacerbated as the complexity of the external environment increases. For example, in the actual monitoring environment, factors such as temperature fluctuations, humidity changes, equipment aging, background clutter, and inter-channel coupling interference make the system error show obvious time-varying characteristics, greatly restricting the actual measurement accuracy of MIMO-GBSAR. Therefore, a dynamic calibration method with high anti-interference ability, convenience, and robustness is needed.
[0004] Most of the existing traditional calibration methods rely on ideal and stable environmental conditions, such as microwave anechoic chambers. Although this method has high accuracy, it lacks sufficient robustness and flexibility in complex on-site environments, is difficult to effectively extract reference target information, and is also difficult to eliminate background clutter and coupling interference, resulting in a significant decline in the calibration effect during actual application.
[0005] In view of the above problems, it is urgent to study a calibration method for the MIMO-GBSAR system suitable for complex environmental conditions to improve the on-site adaptability and actual measurement accuracy of the system. Therefore, in response to the above problems, the present invention innovatively proposes a method capable of realizing error calibration of the MIMO-GBSAR system in a near-distance complex environment. Summary of the Invention
[0006] The present application provides a near - distance calibration method for a multiple - input multiple - output ground - based synthetic aperture radar to solve the problems of poor robustness and difficulty in effectively dealing with the time - variability of system errors in the traditional calibration method of the MIMO - GBSAR system in a complex field environment.
[0007] In the first - aspect embodiment of the present application, a near - distance calibration method for a multiple - input multiple - output ground - based synthetic aperture radar includes the following steps: Obtain the original radar echo data of the multiple - input multiple - output ground - based synthetic aperture radar, and use the multiple - input multiple - output ground - based synthetic aperture radar to perform spatial domain measurement on the sky to obtain the coupled interference signal data of the multiple - input multiple - output ground - based synthetic aperture radar; perform digital cancellation processing on the original radar echo data and the coupled interference signal data to eliminate the coupled interference between the channels of the multiple - input multiple - output ground - based synthetic aperture radar, so as to obtain the radar echo data after eliminating the coupled interference; based on the radar echo data after eliminating the coupled interference, adjust the radar signal bandwidth of the multiple - input multiple - output ground - based synthetic aperture radar to obtain a radar with a broadband configuration, and use the radar with the broadband configuration to perform at least ten measurements on the scene with a reference target placed and the scene without a reference target placed to generate at least ten groups of radar data; perform coherent superposition on the at least ten groups of radar data to generate the radar echo data of the scene with a reference target placed after coherent accumulation and the radar echo data of the scene without a reference target placed after coherent accumulation; perform digital cancellation processing on the radar echo data of the scene with a reference target placed after coherent accumulation and the radar echo data of the scene without a reference target placed after coherent accumulation to generate broadband echo data after eliminating the mutual - coupling interference signal and the background clutter interference signal; perform band - pass filtering processing on the broadband echo data to generate broadband echo data after eliminating the additive error; based on the broadband echo data after eliminating the additive error, generate ideal point - target echo signal data according to the measured distance between the reference target and the multiple - input multiple - output ground - based synthetic aperture radar, and divide the ideal point - target echo signal data by the filtered signal to determine the calibration data under the broadband configuration; perform data fitting on the calibration data under the broadband configuration to generate calibration data that meets the preset narrow - band conditions; based on the original radar echo signal after eliminating the coupling error and the calibration data, obtain the calibrated original radar data.
[0008] Optionally, in an embodiment of the present application, the calculation formula for the radar echo data after eliminating the coupled interference is:
[0009]
[0010] where s narrow (n,m,t) is the radar echo signal under the narrow - band configuration, s couple (n,m,t) is the non - ideal coupling signal, A0 is the amplitude of the echo signal, A enmis the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents time, f0 is the carrier frequency of the reflected signal, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, t tX and t RX are both time delays, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, n is the transmitting channel serial number, m is the receiving channel serial number, N w is Gaussian white noise.
[0011] Optionally, in an embodiment of the present application, the calculation formula for the radar echo data without a reference target in the at least ten groups of radar data is:
[0012]
[0013] wherein, A0 is the amplitude of the echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents the time, is the distance between the transmitting antenna n and the receiving antenna m, c is the speed of light in vacuum, t TX and t RX are both the time delays, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, n is the transmitting channel serial number, m is the receiving channel serial number, i represents the i-th group of echo data, N w is the Gaussian white noise, N BG is the background noise.
[0014] Optionally, in an embodiment of the present application, the calculation formula for the broadband echo data eliminating the mutual coupling interference signal and the background clutter interference signal is:
[0015]
[0016] wherein, s Broad (n,m,t) is the radar echo data with a reference target after coherent accumulation, s BG (n,m,t) is the radar echo data without a reference target after coherent accumulation, A enm is the amplitude error of the transmitting channel n and the receiving channel m, A0 is the amplitude of the echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, wr is the distance - direction window function, t represents the time, is the distance between the target and the n - th transmitting antenna unit, is the distance between the target and the m - th receiving antenna unit, c is the speed of light propagating in the vacuum, is the distance between the target and the n - th transmitting antenna unit, is the distance between the target and the m - th receiving antenna unit, t TX and t RX are both the time delays, n is the serial number of the transmitting channel, m is the serial number of the receiving channel, is the phase error of the n - th transmitting channel, is the phase error of the m - th receiving channel, M res is the residual interference signal.
[0017] Optionally, in an embodiment of the present application, the calculation formula of the broadband echo data after eliminating the additive error is:
[0018]
[0019] where, A0 is the amplitude of the echo signal, A enm is the amplitude of the n - th transmitting channel and the m - th receiving channel, w r is the distance - direction window function, t represents the time, is the distance between the target and the n - th transmitting antenna unit, is the distance between the target and the m - th receiving antenna unit, c is the speed of light propagating in the vacuum, is the distance between the target and the n - th transmitting antenna unit, is the distance between the target and the m - th receiving antenna unit, t TX and t RX are both the time delays, n is the serial number of the transmitting channel, m is the serial number of the receiving channel, is the phase error of the n - th transmitting channel, is the phase error of the m - th receiving channel.
[0020] Optionally, in an embodiment of the present application, the calculation formula of the calibration data under the broadband configuration is:
[0021]
[0022] where, is the broadband echo signal after eliminating the additive error, s ideal (n,m,t) is the echo signal of an ideal point target, A enmare the amplitudes of the transmitting channel n and the receiving channel m, w r is the range window function, t represents the time, t TX and t RX are both the time delays, n is the transmitting channel number, m is the receiving channel number, is the phase error of the transmitting channel n, is the phase error of the receiving channel m.
[0023] Optionally, in an embodiment of the present application, the calculation formula for the calibration data satisfying the preset narrowband condition is:
[0024]
[0025] where n is the transmitting channel number, m is the receiving channel number, and t represents the time.
[0026] Optionally, in an embodiment of the present application, the calculation formula for the calibrated radar raw data is:
[0027]
[0028] where, is the measured radar echo signal after coupling error cancellation, s Narrow-cal (n, m, t) is the radar calibration data under narrowband configuration, A0 is the amplitude of the echo signal, w r is the range window function, t represents the time, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, n is the transmitting channel number, m is the receiving channel number, c is the speed of light in vacuum, N w is the Gaussian white noise.
[0029] The second aspect of the present application provides a near - field calibration device for a multiple - input multiple - output (MIMO) ground - based synthetic aperture radar, including: an acquisition module, configured to acquire the original radar echo data of the MIMO ground - based synthetic aperture radar, and perform spatial domain measurement on the sky using the MIMO ground - based synthetic aperture radar to obtain the coupled interference signal data of the MIMO ground - based synthetic aperture radar; an elimination module, configured to perform digital cancellation processing on the original radar echo data and the coupled interference signal data to eliminate the coupled interference between the channels of the MIMO ground - based synthetic aperture radar, so as to obtain the radar echo data after eliminating the coupled interference; a measurement module, configured to adjust the radar signal bandwidth of the MIMO ground - based synthetic aperture radar based on the radar echo data after eliminating the coupled interference to obtain a radar with a broadband configuration, and use the radar with the broadband configuration to perform at least ten measurements on the scene with a reference target placed and the scene without a reference target placed, so as to generate at least ten sets of radar data; a coherent superposition module, configured to perform coherent superposition on the at least ten sets of radar data to generate the radar echo data of the scene with a reference target placed after coherent accumulation and the radar echo data of the scene without a reference target placed after coherent accumulation; a cancellation processing module, configured to perform digital cancellation processing on the radar echo data of the scene with a reference target placed after coherent accumulation and the radar echo data of the scene without a reference target placed after coherent accumulation to generate broadband echo data after eliminating the mutual coupling interference signal and the background clutter interference signal; a band - pass filtering processing module, configured to perform band - pass filtering processing on the broadband echo data to generate broadband echo data after eliminating the additive error; a generation module, configured to generate ideal point - target echo signal data based on the broadband echo data after eliminating the additive error according to the measured distance between the reference target and the MIMO ground - based synthetic aperture radar, and divide the ideal point - target echo signal data by the filtered signal to determine the calibration data under the broadband configuration; a data fitting module, configured to perform data fitting on the calibration data under the broadband configuration to generate calibration data that meets the preset narrow - band conditions; a calibration module, configured to obtain the calibrated original radar data based on the original radar echo signal after eliminating the coupling error and the calibration data.
[0030] Optionally, in an embodiment of the present application, the calculation formula for the radar echo data after eliminating the coupled interference is:
[0031]
[0032] where s Narrow (n,m,t) is the radar echo signal under the narrow - band configuration, s couple (n,m,t) is the non - ideal coupling signal, A0 is the amplitude of the echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, w ris the range window function, t represents time, f0 is the carrier frequency of the reflected signal, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, t TX and t RX are both time delays, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, n is the transmitting channel serial number, m is the receiving channel serial number, N w is Gaussian white noise.
[0033] Optionally, in an embodiment of the present application, the calculation formula for the radar echo data without a reference target in the at least ten groups of radar data is:
[0034]
[0035] where A0 is the amplitude of the echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents the time, is the distance between the transmitting antenna n and the receiving antenna m, c is the speed of light in a vacuum, t TX and t RX are both the time delays, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, n is the transmitting channel serial number, m is the receiving channel serial number, i represents the i-th group of echo data, N w is the Gaussian white noise, N BG is the background noise.
[0036] Optionally, in an embodiment of the present application, the calculation formula for the broadband echo data eliminating the mutual coupling interference signal and the background clutter interference signal is:
[0037]
[0038] where s Broad (n,m,t) is the radar echo data with a reference target after coherent accumulation, s BG (n,m,t) is the radar echo data without a reference target after coherent accumulation, A enm is the amplitude error of the transmitting channel n and the receiving channel m, A0 is the amplitude of the echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents the time, is the distance between the target and the transmitting antenna unit n, is the distance between the target and the receiving antenna unit m, and c is the speed of light propagating in the vacuum, is the distance between the target and the transmitting antenna unit n, is the distance between the target and the receiving antenna unit m, t TX and t RX are both the time delays, n is the transmitting channel serial number, and m is the receiving channel serial number, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, N res is the residual interference signal.
[0039] Optionally, in an embodiment of the present application, the calculation formula of the broadband echo data after eliminating the additive error is:
[0040]
[0041] where A0 is the amplitude of the echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents the time, is the distance between the target and the transmitting antenna unit n, is the distance between the target and the receiving antenna unit m, and c is the speed of light propagating in the vacuum, is the distance between the target and the transmitting antenna unit n, is the distance between the target and the receiving antenna unit m, t TX and t RX are both the time delays, n is the transmitting channel serial number, and m is the receiving channel serial number, is the phase error of the transmitting channel n, is the phase error of the receiving channel m.
[0042] Optionally, in an embodiment of the present application, the calculation formula of the calibration data under the broadband configuration is:
[0043]
[0044] where, is the broadband echo signal after eliminating the additive error, s ideal (n,m,t) is the target echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, w ris the range window function, t represents the time, t TX and t RX are both the time delays, n is the transmitting channel number, m is the receiving channel number, is the phase error of the transmitting channel n, is the phase error of the receiving channel m.
[0045] Optionally, in an embodiment of the present application, the calculation formula for the calibration data satisfying the preset narrowband condition is:
[0046]
[0047] where n is the transmitting channel number, m is the receiving channel number, and t represents the time.
[0048] Optionally, in an embodiment of the present application, the calculation formula for the calibrated radar raw data is:
[0049]
[0050] where, is the measured radar echo signal after eliminating the coupling error, s Narrow-cal (n,m,t) is the radar calibration data under narrowband configuration, A0 is the amplitude of the echo signal, w r is the range window function, t represents the time, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, n is the transmitting channel number, m is the receiving channel number, c is the speed of light in vacuum, N w is the Gaussian white noise.
[0051] In the embodiments of the present application, by adjusting the radar transmission signal, it is extended from LFMCW (Linear Frequency Modulated Continuous Wave, narrowband linear frequency modulated continuous wave) to a broadband LFMCW signal to improve the resolution of the radar system, and thus more effectively extract reference target information. At the same time, an external calibration technology is adopted to obtain error compensation data, and the compensation data under broadband signal conditions is fitted and converted into the actual narrowband measurement conditions through data fitting, thereby realizing system calibration in complex environments. Thereby, the problems of poor robustness and difficulty in effectively coping with the time-variation of system errors in the traditional MIMO-GBSAR system calibration method in complex field environments are solved.
[0052] Additional aspects and advantages of the present application will be given in part in the following description, become apparent in part from the following description, or be learned through the practice of the present application. BRIEF DESCRIPTION OF THE DRAWINGS
[0053] The above-mentioned and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description of embodiments in conjunction with the drawings, where:
[0054] Figure 1 FIG. is a schematic diagram of a receiving and transmitting channel structure of a MIMO-GBSAR according to an embodiment of the present application;
[0055] Figure 2 FIG. is a flowchart of a near-field calibration method for a multiple-input multiple-output ground-based synthetic aperture radar provided according to an embodiment of the present application;
[0056] Figure 3 FIG. is a flowchart of a near-field calibration method for a MIMO-GBSAR system in a complex environment according to an embodiment of the present application;
[0057] Figure 4 FIG. is a comparison diagram of the imaging effects after calibrating radar raw data by a traditional calibration method and a patented calibration method according to an embodiment of the present application;
[0058] Figure 5 FIG. is a schematic diagram of the structure of a near-field calibration device for a multiple-input multiple-output ground-based synthetic aperture radar provided according to an embodiment of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0059] Embodiments of the present application will be described in detail below. Examples of the embodiments are shown in the drawings, where the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the drawings are exemplary and are intended to explain the present application and should not be construed as limiting the present application.
[0060] The following describes a near - range calibration method for a multiple - input multiple - output (MIMO) ground - based synthetic aperture radar (GBSAR) according to an embodiment of the present application. Aiming at the problems of poor robustness and difficulty in effectively coping with the time - variability of system errors in the traditional calibration method of the MIMO - GBSAR system mentioned in the above - mentioned background technology, the present application provides a near - range calibration method for a MIMO ground - based synthetic aperture radar. In this method, by adjusting the radar transmission signal, it is extended from a LFMCW signal to a wide - band LFMCW signal to improve the resolution of the radar system, and then more effectively extract the reference target information. At the same time, an external calibration technology is used to obtain error compensation data, and the compensation data under the wide - band signal condition is fitted and converted into the actual narrow - band measurement condition through data fitting, so as to realize the system calibration in a complex environment. Thus, the problems of poor robustness and difficulty in effectively coping with the time - variability of system errors in the traditional calibration method of the MIMO - GBSAR system are solved.
[0061] The present application provides a near - range calibration method for a MIMO ground - based synthetic aperture radar. Table 1 in the method is a symbol table, where, as shown in Table 1:
[0062] Table 1
[0063]
[0064]
[0065] Before introducing the specific implementation manner, first, an error signal model of the MIMO - GBSAR system is given. The MIMO - GBSAR system includes 12 transmitting antenna elements and 16 receiving antenna elements. Here, error analysis is carried out taking one set of transmitting and receiving antennas as an example. First, for a radar with LFMCW system, the radar transmission signal is defined as shown in formula (1), and the transmission gain is ignored here.
[0066]
[0067] Among them, s tx (·) represents the transmission signal; t represents time; w r is the range window function, usually a rectangular window function; f0 is the carrier frequency of the LFMCW signal; K is the frequency modulation rate of the LFMCW signal. The transmission signal is radiated into free space through the antenna. After propagating a distance of R T , it encounters a target and scatters. Part of the scattered signal propagates along the radar direction and is received by the receiving antenna after passing a distance of R R . At this time, the target - scattered signal received by the radar will have a certain time delay relative to the transmission signal. As shown in formula (2).
[0068]
[0069] Among them, s rx (·) represents the received signal; τ is the round-trip delay of the radar signal from transmission to the target and then to reception, as shown in Equation (3).
[0070]
[0071] Among them, c represents the speed of light in a vacuum. For a radar with an LFMCW system, demodulation is to directly mix the received signal with the transmitted signal and with the quadrature signal of the transmitted signal to achieve IQ demodulation. As shown in Equation (4) and Equation (5).
[0072]
[0073] Among them, s I (t) and s Q (t) represent the in-phase component and the quadrature component after mixing respectively. In actual operation, the duration of the transmitted signal covers the entire reception process, so the result of multiplying the two window functions here is w r (t - τ). At the same time, s rxQ (·) in Equation (5) represents the quadrature signal obtained by shifting the transmitted signal by 90 degrees in phase.
[0074] Here, the signal after mixing is further low-pass filtered to remove the high-frequency part, as shown in Equations (6) and (7).
[0075]
[0076] According to Euler's formula, the signal can be written in exponential form, as shown in Equation (8).
[0077]
[0078] Among them, s(·) is the echo signal after radar demodulation. At this time, there are still problems with the signal being skewed and the part exp(jπKτ 2 ) called the video residual term. It is necessary to perform "deskewing" processing on the signal to eliminate the influence. Perform a Fourier transform on the signal, as shown in Equation (9).
[0079]
[0080] In Equation (9) The third phase component exp(-j2πfτ) is the skewed term; S(·) represents the frequency-domain signal of the echo signal s(t); T p represents the duration of a single chirp of the LFMCW signal. The "deskewing" operation needs to compensate for the video residual term and the skewed term, and the compensation term is as shown in Equation (10).
[0081] H(f) = exp(-jπKτ 2 )exp(j2πfτ)(10)
[0082] Where H(·) is the frequency-domain expression of the compensation term.
[0083] Multiply formula (9) by the compensation term and perform the inverse Fourier transform to obtain the final echo data, as shown in formula (11).
[0084]
[0085] Ideally, represent the signal amplitude as A0, expand τ, and substitute the channel number into the formula. The ideal echo signal can be expressed as formula (12).
[0086]
[0087] Where s ideal (·) is the ideal echo signal; n and m represent the nth transmit channel and the mth receive channel respectively; and are the distances between the target and the nth transmit antenna element and between the target and the mth receive antenna element respectively.
[0088] The system errors of MIMO-GBSAR are mainly divided into two types: additive errors and multiplicative errors. Additive errors include inter-channel coupling, background clutter, and random noise. Multiplicative errors include the amplitude-frequency and phase-frequency responses of the LFMCW signal, amplitude and phase imbalance between channels, and on-chip transmission delay of signals between channels.
[0089] The structure of the nth transmit and mth receive channels of the MIMO-GBSAR system and the time delay of the entire system are as Figure 1 shown. The radar signal is radiated from the transmit antenna element after mixing, filtering, and amplification, and this process takes time t TX ( Figure 1 a), which is the time delay brought by the entire transmit channel; the transmitted radar signal reaches the target after a period of time, and the time required for this process is ( Figure 1 b); the transmitted signal is scattered after encountering the target, and a part of the scattered signal is received by the receive antenna element after time ( Figure 1 c); finally, the received signal enters the analog-to-digital converter for sampling after being amplified by the low-noise amplifier, mixed, and filtered by the low-pass filter, and the time experienced in this process can be expressed as t RX ( Figure 1 d). The time delays caused by the transmit and receive channels in this part of the time delay are unnecessary, that is, the error terms.
[0090] Upon further analysis, according to Figure 1 it can be known that the transmitted signal can be received by the receiving antenna not only after being scattered by the target. Since the MIMO-GBSAR system is a single-site coherent radar system, the distance between the transmitting and receiving antennas of the system is relatively close, which results in part of the transmitted signal directly radiating from the transmitting antenna to the receiving antenna. This is the coupling phenomenon between the transmitting and receiving antenna elements of the MIMO-GBSAR system. And the mutual coupling between antennas also takes a certain amount of time, which can be defined as t c ( Figure 1 e), and this time is generally considered to be the propagation delay of the electromagnetic wave caused by the distance between the transmitting and receiving antennas. As shown in formula (13).
[0091]
[0092] Among them, represents the distance between the nth transmitting antenna and the mth receiving antenna. According to the above analysis, it can be known that for the nth transmitting and the mth receiving channels, there is also a mutual coupling signal between the transmitting and receiving antennas. This signal also passes through the transmitting and receiving channels, generating corresponding time delays. However, different from general targets, the propagation delay of this signal in free space is t c , and only by replacing the propagation delay of the signal from the transmitting antenna to the target and then from the target to the receiving antenna in formula (12) with the mutual coupling delay t c , the model of the ideal mutual coupling signal s c (·) can be obtained, as shown in formula (14).
[0093]
[0094] The internal delay of the system will also affect the mutual coupling signal. At the same time, there are also certain gain errors in the devices in the receiving and transmitting channels, which results in differences in the amplitudes between different channels of the received signal. Therefore, it is assumed here that the amplitude error existing in the nth transmitting and the mth receiving channels is A enm .
[0095] Since the electronic devices in the transmitting and receiving channels have phase-frequency responses, that is, for different channels and different signal frequencies, the transmitting channel and the receiving channel will respectively superimpose an additional phase component on the signal. Here, the phase error introduced by the transmitting channel is defined as The phase error introduced by the receiving channel is defined as Its influence is expressed as
[0096] Finally, considering that there will be certain Gaussian white noise in the MIMO-GBSAR system during the actual measurement process, and for the calibration scenario, there is also background noise. Here, the Gaussian white noise is defined as N w , and the background noise is defined as N BG .
[0097] Therefore, in summary, the non-ideal echo signal of the MIMO-GBSAR system containing errors can be expressed in the form of formula (15). Where s represents the non-ideal echo signal. Since the transmit signal bandwidth will be changed later, but the signal model will not change, then s Broad and s Narrow are used to represent the echo data in the wideband configuration and the echo data in the narrowband configuration respectively.
[0098]
[0099] Specifically, Figure 2 is a schematic flow chart of a near-field calibration method for a multiple-input multiple-output ground-based synthetic aperture radar provided by an embodiment of the present application.
[0100] As Figure 2 shown, the near-field calibration method for a multiple-input multiple-output ground-based synthetic aperture radar includes the following steps:
[0101] In step S201, the original radar echo data of the multiple-input multiple-output ground-based synthetic aperture radar is obtained, and the multiple-input multiple-output ground-based synthetic aperture radar is used to perform airspace measurement on the sky to obtain the coupled interference signal data of the multiple-input multiple-output ground-based synthetic aperture radar.
[0102] During the actual execution process, as Figure 3 shown, the embodiment of the present application can configure the MIMO-GBSAR system according to the actual application, measure the target to be actually measured and collect the original radar echo data to obtain the original echo data s Narrow (n, m, t), whose form is as shown in formula (15). At the same time, the radar is used to measure the sky under the same configuration to obtain the coupled interference signal, and the coupled interference signal data is as shown in formula (16).
[0103] The embodiment of the present application can collect the original radar data under the actual MIMO-GBSAR application configuration, and at the same time use the multiple-input multiple-output ground-based synthetic aperture radar to perform airspace measurement on the sky to obtain the coupled interference signal.
[0104] Among them, the calculation formula of the coupled interference signal data is:
[0105]
[0106] where, A0 is the amplitude of the echo signal, A enm is the amplitude of the transmit channel n and the receive channel m, w r is the range window function, t represents time, f0 is the carrier frequency of the reflected signal, is the distance between the transmit antenna n and the receive antenna m, t TX and t RX are both time delays, is the phase error of the transmit channel n, is the phase error of the receive channel m, n is the transmit channel number, m is the receive channel number, N w is Gaussian white noise, s couple (·) represents the non-ideal coupling signal.
[0107] In step S202, digital cancellation processing is performed on the original radar echo data and the coupled interference signal data to eliminate the coupled interference between the multiple-input multiple-output ground-based synthetic aperture radar channels, so as to obtain the radar echo data after eliminating the coupled interference.
[0108] Specifically, the embodiments of the present application can perform digital cancellation processing on the original radar echo data and the coupled interference signal data to eliminate the coupled interference between the multiple-input multiple-output ground-based synthetic aperture radar MIMO-GBSAR channels, so as to obtain the radar echo data after eliminating the coupled interference, as shown in formula (17).
[0109] Among them, in an embodiment of the present application, the calculation formula of the radar echo data after eliminating the coupled interference is:
[0110]
[0111] Among them, s Narrow (n, m, t) is the radar echo signal under the narrowband configuration, corresponding to the original radar echo data, s couple (n, m, t) is the non-ideal coupling signal, A0 is the amplitude of the echo signal, A enm is the amplitude of the transmit channel n and the receive channel m, w r is the range window function, t represents time, f0 is the carrier frequency of the reflected signal, is the distance between the target and the transmit antenna element n, is the distance between the target and the receive antenna element m, t TX and t RX are both time delays, is the phase error of the transmit channel n, is the phase error of the receive channel m, n is the transmit channel number, m is the receive channel number, N w is Gaussian white noise.
[0112] In the embodiments of the present application, represents the measured radar data after eliminating the mutual coupling interference. Since N w is random, the N w in two measurements is different and cannot be directly eliminated. At the same time, for actual tests, N BG does not belong to clutter interference and is only considered as interference during the calibration process. Therefore, the measured echo data does not include this item. At the same time, Gaussian white noise does not affect the channel consistency, so it does not need to be processed during calibration.
[0113] In step S203, based on the radar echo data after eliminating the coupling interference, adjust the radar signal bandwidth of the multiple-input multiple-output ground synthetic aperture radar to obtain a radar with a broadband configuration, and use the radar with the broadband configuration to measure at least ten times the scenarios with and without a reference target placed, so as to generate at least ten groups of radar data.
[0114] In the actual execution process, the embodiments of the present application can expand the radar signal bandwidth to obtain a radar with a broadband configuration, use the radar with the broadband configuration to measure multiple times the scenarios with and without a reference target placed, obtain multiple groups of radar data, adjust the radar transmit signal bandwidth, adjust the relatively narrow bandwidth during remote measurement to a broadband to improve the range resolution of the system and narrow its measurement range. Place a corner reflector at a position about 5 meters directly in front of the radar as a reference target. Collect N groups of data with and without a reference target placed respectively under the broadband configuration, usually 20 groups. The echo data with a reference target placed is s Broad (n,m,t,i), and its form is as shown in formula (15), where i represents the i-th group of echo data. The echo data without a reference target placed is the background clutter and coupling signal, as shown in formula (18).
[0115] The embodiments of the present application expand the narrowband LFMCW of the long-distance test signal to a broadband signal, improve the resolution of the system, and thus extract the reference target information more easily and accurately, overcoming the defect that it is difficult to accurately extract the reference target by traditional narrowband methods in complex environments.
[0116] Among them, in an embodiment of the present application, the calculation formula for the radar echo data without a reference target placed in at least ten groups of radar data is:
[0117]
[0118] where A0 is the amplitude of the echo signal, and A enm is the amplitude of the transmit channel n and the receive channel m, w r is the range window function, t represents time, is the distance between the transmitting antenna n and the receiving antenna m, c is the speed of light in vacuum, and t TX and t RX are both time delays, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, n is the serial number of the transmitting channel, m is the serial number of the receiving channel, i represents the i-th group of echo data, and N w is Gaussian white noise, and N BG is the background noise, and s BG (·) represents the background echo data.
[0119] In step S204, at least ten groups of radar data are coherently superimposed to generate the radar echo data of the placed reference target after coherent accumulation and the radar echo data of the unplaced reference target after coherent accumulation.
[0120] As a possible implementation manner, the embodiments of the present application can coherently accumulate the N groups of echo data of the placed reference target and the radar echo data of the unplaced reference target in the broadband configuration to generate the radar echo data of the placed reference target after coherent accumulation and the radar echo data of the unplaced reference target after coherent accumulation, so as to suppress Gaussian white noise and improve the signal-to-noise ratio. The specific method is shown in formulas (19) and (20).
[0121] Among them, the calculation formulas of the radar echo data of the placed reference target after coherent accumulation and the radar echo data of the unplaced reference target after coherent accumulation are respectively:
[0122]
[0123] Among them, s Broad (n, m, t, i) is the radar echo data of the placed reference target after coherent accumulation, that is, the radar echo data of the placed reference target measured by the radar in the broadband configuration, and s BG (n, m, t, i) is the radar echo data of the unplaced reference target after coherent accumulation, that is, the background echo data after coherent accumulation. n is the serial number of the transmitting channel, m is the serial number of the receiving channel, t represents time, and i represents the i-th group of echo data.
[0124] In step S205, the radar echo data of the placed reference target after coherent accumulation and the radar echo data of the unplaced reference target after coherent accumulation are digitally canceled to generate broadband echo data that eliminates the mutual coupling interference signal and the background clutter interference signal.
[0125] In the actual execution process, the embodiment of the present application can perform digital cancellation processing on the echo data with the reference target placed after coherent accumulation and the radar echo data without the reference target placed after coherent accumulation to generate broadband echo data that eliminates the mutual coupling interference signal and the background clutter interference signal, so as to eliminate the mutual coupling interference signal and the background clutter interference signal. The processing process is shown in formula (21).
[0126] Among them, in an embodiment of the present application, the calculation formula for the broadband echo data that eliminates the mutual coupling interference signal and the background clutter interference signal is as follows:
[0127]
[0128] Among them, s Broad (n,m,t) is the radar echo data with the reference target placed after coherent accumulation, s BG (n,m,t) is the radar echo data without the reference target placed after coherent accumulation, A enm is the amplitude error between the transmitting channel n and the receiving channel m, A0 is the amplitude of the echo signal, A enm is the amplitude between the transmitting channel n and the receiving channel m, w r is the range window function, t represents time, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, c is the speed of light in a vacuum, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, t TX and t RX are both time delays, n is the transmitting channel number, m is the receiving channel number, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, N res is the residual interference signal, which is mainly caused by the change of the measurement background in the complex environment compared with the actual measurement background.
[0129] In step S206, band-pass filtering processing is performed on the broadband echo data to generate broadband echo data after eliminating the additive error.
[0130] Specifically, formula (21) in the embodiment of the present application is a single-frequency signal with a frequency of , and this frequency is mainly related to the target position. Therefore, a band-pass filter can be designed according to the actual position of the reference target, and band-pass filtering processing is performed on the broadband echo data to filter out the pure reference target information and eliminate the residual interference signal, that is, generate broadband echo data after eliminating the additive error. As shown in formula (22).
[0131] Among them, in one embodiment of the present application, the calculation formula for the broadband echo data after eliminating the additive error is:
[0132]
[0133] Among them, A0 is the amplitude of the echo signal, and A enm is the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents time, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, c is the speed of light in a vacuum, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, t TX and t RX are both time delays, n is the transmitting channel number, m is the receiving channel number, is the phase error of the transmitting channel n, is the phase error of the receiving channel m.
[0134] In step S207, based on the broadband echo data after eliminating the additive error, ideal point target echo signal data is generated according to the measured distance between the reference target and the multiple-input multiple-output ground-based synthetic aperture radar, and the ideal point target echo signal data is divided by the filtered signal to determine the calibration data in the broadband configuration.
[0135] In the actual execution process, the embodiment of the present application can generate ideal point target echo signal data based on the broadband echo signal after eliminating the additive error, using the measured distance between the reference target and the multiple-input multiple-output ground-based synthetic aperture radar, and divide it by the filtered signal to obtain the calibration data in the broadband configuration. As shown in formula (23).
[0136] Among them, in one embodiment of the present application, the calculation formula for the calibration data in the broadband configuration is:
[0137]
[0138] Among them, is the broadband echo signal after eliminating the additive error, s ideal (n,m,t) is the ideal point target echo signal, that is, the ideal echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents time, t TX and t RX are both time delays, n is the transmitting channel number, m is the receiving channel number, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, s Broad-cal (·) represents the calibration data under broadband configuration conditions.
[0139] In step S208, the calibration data under broadband configuration is subjected to data fitting to generate calibration data that meets the preset narrowband conditions.
[0140] As a possible implementation, the calibration data under broadband configuration (conditions) in the embodiments of the present application is converted into calibration data applicable to narrowband conditions through data fitting (such as spline interpolation). As shown in formula (24).
[0141] The embodiments of the present application effectively convert broadband calibration data into narrowband test data through data fitting, significantly improving the generality and flexibility of the calibration method, reducing the requirements for the calibration environment, and simplifying the calibration operation in actual engineering. The external calibration technology is used to obtain error compensation data, and the compensation data under broadband signal conditions is fitted and converted into actual narrowband measurement conditions through data fitting, thereby realizing system calibration in complex environments.
[0142] Among them, in an embodiment of the present application, the calculation formula for the calibration data that meets the preset narrowband conditions is:
[0143]
[0144] where n is the transmitting channel number, m is the receiving channel number, t represents time, s Narrow-cal (·) represents the calibration data under narrowband configuration conditions.
[0145] In step S209, based on the original radar echo signal after coupling error cancellation and the calibration data, the calibrated radar raw data is obtained.
[0146] In the actual execution process, the embodiments of the present application can divide the measured radar echo signal after coupling error cancellation by the calibration data applicable to narrowband conditions to achieve channel normalization, complete the entire calibration process, and obtain the calibrated radar raw data, which can achieve fast and efficient calibration in complex actual application environments and has high environmental adaptability and robustness. As shown in formula (25).
[0147] The embodiments of the present application transfer the calibration process to the close-range condition, quickly and effectively extract reference target information, timely capture and compensate for the time-varying system error caused by environmental factors, greatly enhancing the adaptability and accuracy of the calibration method, thereby improving the performance and reliability of the MIMO-GBSAR system in actual applications. The final calibration effect is as Figure 4 shown.
[0148] Among them, in one embodiment of the present application, the calculation formula of the corrected radar raw data is as follows:
[0149]
[0150] Among them, is the measured radar echo signal after coupling error elimination, s Narrow-cal (n,m,t) is the radar correction data under narrowband configuration, A0 is the amplitude of the echo signal, w r is the range window function, t represents time, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, n is the transmitting channel number, m is the receiving channel number, c is the speed of light in vacuum, N w is Gaussian white noise.
[0151] A near-field calibration method for a multiple-input multiple-output ground-based synthetic aperture radar according to an embodiment of the present application transfers the calibration process to near-field conditions, quickly and effectively extracts reference target information, timely captures and compensates for time-varying system errors caused by environmental factors, greatly enhances the adaptability and accuracy of the calibration method, and thus improves the performance and reliability of the MIMO-GBSAR system in practical applications. Thereby, the problems of poor robustness and difficulty in effectively coping with the time-variation of system errors in the calibration method of the traditional MIMO-GBSAR system are solved.
[0152] Next, a near-field calibration device for a multiple-input multiple-output ground-based synthetic aperture radar according to an embodiment of the present application is described with reference to the accompanying drawings.
[0153] Figure 5 is a schematic structural diagram of a near-field calibration device for a multiple-input multiple-output ground-based synthetic aperture radar according to an embodiment of the present application.
[0154] As Figure 5 shown, the near-field calibration device 10 for a multiple-input multiple-output ground-based synthetic aperture radar includes: an acquisition module 100, an elimination module 200, a measurement module 300, a coherent superposition module 400, a cancellation processing module 500, a band-pass filtering processing module 600, a generation module 700, a data fitting module 800, and a calibration module 900.
[0155] Specifically, the acquisition module 100 is configured to acquire the original radar echo data of the multiple-input multiple-output ground-based synthetic aperture radar, and perform spatial domain measurement on the sky using the multiple-input multiple-output ground-based synthetic aperture radar to acquire the coupled interference signal data of the multiple-input multiple-output ground-based synthetic aperture radar.
[0156] Cancellation module 200 is used to perform digital cancellation processing on the original radar echo data and the coupled interference signal data, eliminate the coupled interference between the multiple-input multiple-output (MIMO) ground-based synthetic aperture radar channels, and obtain the radar echo data after eliminating the coupled interference.
[0157] Measurement module 300 is used to adjust the radar signal bandwidth of the MIMO ground-based synthetic aperture radar based on the radar echo data after eliminating the coupled interference, so as to obtain a radar with a broadband configuration, and use the radar with the broadband configuration to measure at least ten times for the scenarios with and without a reference target placed, so as to generate at least ten sets of radar data.
[0158] Coherent superposition module 400 is used to perform coherent superposition on at least ten sets of radar data to generate the radar echo data of the placed reference target after coherent accumulation and the radar echo data of the non-placed reference target after coherent accumulation.
[0159] Cancellation processing module 500 is used to perform digital cancellation processing on the radar echo data of the placed reference target after coherent accumulation and the radar echo data of the non-placed reference target after coherent accumulation, so as to generate broadband echo data after eliminating the mutual coupling interference signal and the background clutter interference signal.
[0160] Band-pass filtering processing module 600 is used to perform band-pass filtering processing on the broadband echo data to generate broadband echo data after eliminating the additive error.
[0161] Generation module 700 is used to generate ideal point target echo signal data based on the broadband echo data after eliminating the additive error according to the measured distance between the reference target and the MIMO ground-based synthetic aperture radar, and divide the ideal point target echo signal data by the filtered signal to determine the calibration data under the broadband configuration.
[0162] Data fitting module 800 is used to perform data fitting on the calibration data under the broadband configuration to generate calibration data that meets the preset narrowband conditions.
[0163] Calibration module 900 is used to obtain the calibrated original radar data based on the original radar echo signal after eliminating the coupling error and the calibration data.
[0164] Optionally, in an embodiment of the present application, the calculation formula for the radar echo data after eliminating the coupled interference is:
[0165]
[0166] where s Narrow (n,m,t) is the radar echo signal under the narrowband configuration, s couple (n,m,t) is the non-ideal coupling signal, A0 is the amplitude of the echo signal, Aenm is the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents time, f0 is the carrier frequency of the reflected signal, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, t TX and t RX are both time delays, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, n is the transmitting channel number, m is the receiving channel number, N w is Gaussian white noise.
[0167] Optionally, in an embodiment of the present application, the calculation formula for the radar echo data of at least ten groups of radar data without a reference target placed therein is:
[0168]
[0169] where A0 is the amplitude of the echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents time, is the distance between the transmitting antenna n and the receiving antenna m, c is the speed of light in a vacuum, t TX and t RX are both time delays, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, n is the transmitting channel number, m is the receiving channel number, i represents the i-th group of echo data, N w is Gaussian white noise, N BG is background noise.
[0170] Optionally, in an embodiment of the present application, the calculation formula for the broadband echo data eliminating the mutual coupling interference signal and the background clutter interference signal is:
[0171]
[0172] where s Broad (n,m,t) is the radar echo data of the placed reference target measured by the radar using the broadband configuration after coherent accumulation, s BG (n,m,t) is the radar echo data of the unplaced reference target after coherent accumulation, A enm is the amplitude error of the transmitting channel n and the receiving channel m, A0 is the amplitude of the echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents time is the distance between the target and the transmitting antenna unit n, is the distance between the target and the receiving antenna unit m, and c is the speed of light in vacuum, is the distance between the target and the transmitting antenna unit n, is the distance between the target and the receiving antenna unit m, t TX and t RX are both time delays, n is the transmitting channel number, and m is the receiving channel number, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, N res is the residual interference signal.
[0173] Optionally, in an embodiment of the present application, the calculation formula for the broadband echo data after eliminating the additive error is:
[0174]
[0175] where A0 is the amplitude of the echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents time, is the distance between the target and the transmitting antenna unit n, is the distance between the target and the receiving antenna unit m, c is the speed of light in vacuum, is the distance between the target and the transmitting antenna unit n, is the distance between the target and the receiving antenna unit m, t TX and t RX are both time delays, n is the transmitting channel number, and m is the receiving channel number, is the phase error of the transmitting channel n, is the phase error of the receiving channel m.
[0176] Optionally, in an embodiment of the present application, the calculation formula for the calibration data in the broadband configuration is:
[0177]
[0178] where, is the broadband echo signal after eliminating the additive error, s ideal (n, m, t) is the ideal point target echo signal, A enm is the amplitude of the transmitting channel n and the receiving channel m, w r is the range window function, t represents time, t TX and t RX are both time delays, n is the transmitting channel number, and m is the receiving channel number, is the phase error of the transmission channel n. is the phase error of the reception channel m.
[0179] Optionally, in an embodiment of the present application, the calculation formula for the calibration data satisfying the preset narrowband condition is:
[0180]
[0181] where n is the transmission channel number, m is the reception channel number, and t represents time.
[0182] Optionally, in an embodiment of the present application, the calculation formula for the calibrated radar raw data is:
[0183]
[0184] where is the measured radar echo signal after coupling error cancellation, s Narrow-cal (n, m, t) is the radar calibration data under narrowband configuration, A0 is the amplitude of the echo signal, w r is the range window function, t represents time, is the distance between the target and the transmission antenna element n, is the distance between the target and the reception antenna element m, n is the transmission channel number, m is the reception channel number, c is the speed of light in vacuum, N w is the Gaussian white noise.
[0185] It should be noted that the foregoing explanation of the embodiment of the close-range calibration method for a multiple-input multiple-output ground-based synthetic aperture radar also applies to the close-range calibration device of a multiple-input multiple-output ground-based synthetic aperture radar in this embodiment, and will not be elaborated here.
[0186] According to a close-range calibration device for a multiple-input multiple-output ground-based synthetic aperture radar proposed in an embodiment of the present application, by transferring the calibration process to a close-range condition, the reference target information can be quickly and effectively extracted, the time-varying system error caused by environmental factors can be captured and compensated in a timely manner, and the adaptability and accuracy of the calibration method are greatly enhanced, thereby improving the performance and reliability of the MIMO-GBSAR system in practical applications. Thus, the problems of poor robustness and difficulty in effectively coping with the time-variability of system errors in the traditional calibration method of the MIMO-GBSAR system in a complex field environment are solved.
[0187] In the description of this specification, the descriptions referring to terms such as "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of this application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in any one or N embodiments or examples in a suitable manner. In addition, without contradiction, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.
[0188] In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include at least one of such features. In the description of this application, the meaning of "N" is at least two, such as two, three, etc., unless otherwise specifically defined.
[0189] Any process or method description shown in a flowchart or described in other ways herein can be understood to represent a module, segment, or portion of code including one or N executable instructions for implementing a customized logical function or process, and the scope of the preferred embodiments of this application includes additional implementations, where the functions can be executed in a substantially simultaneous manner or in a reverse order according to the involved functions, rather than in the order shown or discussed, which should be understood by those skilled in the art to which the embodiments of this application pertain.
[0190] Those of ordinary skill in the art of this technology can understand that all or part of the steps carried by the methods of the above embodiments can be completed by instructing relevant hardware through a program, and the program can be stored in a computer-readable storage medium. When the program is executed, it includes one or a combination of the steps of the method embodiments.
[0191] In addition, each functional unit in various embodiments of this application can be integrated into one processing module, or each unit can exist physically alone, or two or more units can be integrated into one module. The above integrated module can be implemented in the form of hardware or in the form of a software functional module. When the integrated module is implemented in the form of a software functional module and sold or used as an independent product, it can also be stored in a computer-readable storage medium.
[0192] The storage medium mentioned above may be a read-only memory, a magnetic disk, an optical disk, etc. Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present application. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present application.
Claims
1. A near - field calibration method for a multiple - input multiple - output ground synthetic aperture radar, characterized in that, Including the following steps: Obtain the original radar echo data of the multiple-input multiple-output (MIMO) ground-based synthetic aperture radar, and use the MIMO ground-based synthetic aperture radar to perform spatial measurement on the sky to obtain the coupled interference signal data of the MIMO ground-based synthetic aperture radar; Perform digital cancellation processing on the original radar echo data and the coupled interference signal data to eliminate the coupled interference between the channels of the MIMO ground-based synthetic aperture radar, so as to obtain the radar echo data after eliminating the coupled interference; Based on the radar echo data after eliminating the coupled interference, adjust the radar signal bandwidth of the MIMO ground-based synthetic aperture radar to obtain a radar with a broadband configuration, and use the radar with the broadband configuration to perform at least ten measurements on the scenarios with and without a reference target placed, so as to generate at least ten sets of radar data; Perform coherent superposition on the at least ten sets of radar data to generate the radar echo data of the placed reference target after coherent accumulation and the radar echo data of the unplaced reference target after coherent accumulation; Perform digital cancellation processing on the radar echo data of the placed reference target after coherent accumulation and the radar echo data of the unplaced reference target after coherent accumulation to generate broadband echo data after eliminating the mutual coupling interference signal and the background clutter interference signal; Perform band-pass filtering processing on the broadband echo data to generate broadband echo data after eliminating the additive error; Based on the broadband echo data after eliminating the additive error, generate ideal point target echo signal data according to the measured distance between the reference target and the MIMO ground-based synthetic aperture radar, and divide the ideal point target echo signal data by the filtered signal to determine the calibration data under the broadband configuration; Perform data fitting on the calibration data under the broadband configuration to generate calibration data that meets the preset narrowband conditions; Based on the original radar echo signal after eliminating the coupling error and the calibration data, obtain the calibrated original radar data.
2. The method according to claim 1, wherein The calculation formula for the radar echo data after eliminating the coupled interference is: where s Narrow (n, m, t) is the radar echo signal under narrowband configuration, s couple (n, m, t) is the non-ideal coupling signal, A0 is the amplitude of the echo signal, A enm is the amplitude of transmit channel n and receive channel m, w r is the range window function, t represents time, f0 is the carrier frequency of the reflected signal, is the distance between the target and transmit antenna element n, is the distance between the target and receive antenna element m, t TX and t RX are both time delays, is the phase error of transmit channel n, is the phase error of receive channel m, n is the transmit channel number, m is the receive channel number, N w is Gaussian white noise.
3. The method according to claim 2, wherein The calculation formula for the radar echo data of the unplaced reference target in the at least ten sets of radar data is: wherein, A0 is the amplitude of the echo signal, and A enm is the amplitude of the transmission channel n and the reception channel m, w r is the range window function, t represents the time, is the distance between the transmitting antenna n and the receiving antenna m, c is the speed of light in vacuum, t TX and t RX are both the time delays, is the phase error of the transmission channel n, is the phase error of the reception channel m, n is the serial number of the transmission channel, m is the serial number of the reception channel, i represents the i-th group of echo data, N w is the Gaussian white noise, and N BG is the background noise.
4. The method according to claim 3, wherein The calculation formula for the broadband echo data after eliminating the mutual coupling interference signal and the background clutter interference signal is: Among them, s Broad (n, m, t) is the radar echo data of the placed reference target after the coherent accumulation, s BG (n, m, t) is the radar echo data of the unplaced reference target after the coherent accumulation, A enm is the amplitude error between the transmitting channel n and the receiving channel m, A0 is the amplitude of the echo signal, A enm is the amplitude between the transmitting channel n and the receiving channel m, w r is the range window function, t represents the time, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, c is the speed of light propagating in the vacuum, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, t TX and t RX are both the time delays, n is the transmitting channel number, m is the receiving channel number, is the phase error of the transmitting channel n, is the phase error of the receiving channel m, N res is the residual interference signal.
5. The method according to claim 4, characterized in that, The calculation formula for the broadband echo data after eliminating the additive error is: where, A0 is the amplitude of the echo signal, A enm is the amplitude of the transmit channel n and the receive channel m, w r is the range window function, t represents the time, is the distance between the target and the transmit antenna element n, is the distance between the target and the receive antenna element m, c is the speed of light propagating in the vacuum, is the distance between the target and the transmit antenna element n, is the distance between the target and the receive antenna element m, t TX and t RX are both the time delays, n is the transmit channel number, m is the receive channel number, is the phase error of the transmit channel n, is the phase error of the receive channel m.
6. The method according to claim 5, characterized in that, The calculation formula for the calibration data under the broadband configuration is: where s Broad2 (n, m, t) is the wideband echo signal after eliminating the additive error, s ideal (n, m, t) is the ideal point target echo signal, A enm is the amplitude of the transmitting channel m and the receiving channel m, w r is the range window function, t represents the time, t TX and t RX are both the time delays, n is the transmitting channel number, m is the receiving channel number, is the phase error of the transmitting channel n, is the phase error of the receiving channel m.
7. The method according to claim 6, wherein The calculation formula for the calibration data that meets the preset narrowband conditions is: Wherein, n is the transmission channel serial number, m is the reception channel serial number, and t represents the time.
8. The method according to claim 7, wherein The calculation formula for the calibrated original radar data is: Among them, is the measured radar echo signal for the elimination of the coupling error, s Narrow-cal (n, m, t) is the radar calibration data under the narrowband configuration, A0 is the amplitude of the echo signal, w r is the range window function, t represents the time, is the distance between the target and the transmitting antenna element n, is the distance between the target and the receiving antenna element m, n is the transmitting channel number, m is the receiving channel number, c is the speed of light in vacuum, N w is the Gaussian white noise.
9. A near-field correction device for a multiple-input multiple-output ground synthetic aperture radar, characterized in that Including: An acquisition module, configured to obtain the original radar echo data of the MIMO ground-based synthetic aperture radar, and use the MIMO ground-based synthetic aperture radar to perform spatial measurement on the sky to obtain the coupled interference signal data of the MIMO ground-based synthetic aperture radar; An elimination module for performing digital cancellation processing on the original radar echo data and the coupled interference signal data to eliminate the coupled interference between the multiple-input multiple-output ground-based synthetic aperture radar channels, so as to obtain radar echo data after eliminating the coupled interference; A measurement module for adjusting the radar signal bandwidth of the multiple-input multiple-output ground-based synthetic aperture radar based on the radar echo data after eliminating the coupled interference to obtain a radar with a broadband configuration, and using the radar with the broadband configuration to measure at least ten times the scenarios with and without a reference target placed, so as to generate at least ten sets of radar data; A coherent superposition module for coherently superposing the at least ten sets of radar data to generate coherently accumulated radar echo data of the scenario with a reference target placed and coherently accumulated radar echo data of the scenario without a reference target placed; A cancellation processing module for performing digital cancellation processing on the coherently accumulated radar echo data of the scenario with a reference target placed and the coherently accumulated radar echo data of the scenario without a reference target placed to generate broadband echo data after eliminating the mutual coupling interference signal and the background clutter interference signal; A band-pass filtering processing module for performing band-pass filtering processing on the broadband echo data to generate broadband echo data after eliminating the additive error; A generation module for generating ideal point target echo signal data based on the broadband echo data after eliminating the additive error according to the measured distance between the reference target and the multiple-input multiple-output ground-based synthetic aperture radar, and dividing the ideal point target echo signal data by the filtered signal to determine the calibration data under the broadband configuration; A data fitting module for fitting the calibration data under the broadband configuration to generate calibration data that meets the preset narrowband conditions; A calibration module for obtaining the calibrated original radar data based on the original radar echo signal after eliminating the coupling error and the calibration data; 10. The device according to claim 9, characterized in that, The calculation formula for the radar echo data after eliminating the coupled interference is: where s Narrow (n, m, t) is the radar echo signal under narrowband configuration, and s couple (n, m, t) is the non-ideal coupling signal. A0 is the amplitude of the echo signal, and A enm is the amplitude of transmit channel n and receive channel m. w r is the range window function. t represents time, f0 is the carrier frequency of the reflected signal, is the distance between the target and transmit antenna element n, is the distance between the target and receive antenna element m. t TX and t RX are both time delays, is the phase error of transmit channel n, is the phase error of receive channel m. n is the transmit channel number, m is the receive channel number, and N w is the Gaussian white noise.