A near-field precision imaging measurement and calibration method for MIMO radar in time-varying interference environment

Abstract

The present invention discloses a MIMO radar near-field precision imaging measurement and calibration method under a time-varying interference environment. First, the measured target and the calibration body are subjected to simultaneous remote MIMO near-field imaging measurement. The subspace spectrum estimation method is used to obtain the two-dimensional position parameters of the calibration body in the preprocessed two-dimensional image. The scattered echo data of the calibration body is extracted based on the parameterized model characterization method. The channel-by-channel broadband scattering function theoretical value of the calibration body is established according to the scattering characteristics of the calibration body itself and the position relationship of the MIMO radar array element. Finally, the imaging calibration of the measured target is achieved by solving the MIMO array imaging calibration coefficient channel by channel and frequency point by frequency point. The present invention adopts the above-mentioned MIMO radar near-field precision imaging measurement and calibration method under a time-varying interference environment. In the near-field diagnostic imaging measurement of the target using the MIMO radar, the influence of the time-varying interference factors in the measurement environment on the imaging measurement results can be eliminated to a certain extent, thereby improving the accuracy of the MIMO radar near-field imaging measurement.

Description

Technical Field

[0001] The present invention relates to the field of communication and microwave imaging signal technology, and in particular to a near-field precision imaging measurement and calibration method for a MIMO radar in a time-varying interference environment. Background Art

[0002] Multiple Input Multiple Output (MIMO) radar is an emerging radar system that uses limited antenna elements to construct a sparse array and synthesizes a large virtual aperture through clever spatial arrangement of the elements to achieve high-resolution imaging. Compared with traditional turntable inverse synthetic aperture radar (ISAR) imaging measurement and track scanning synthetic aperture radar (SAR) imaging measurement, MIMO near-field imaging measurement radar uses electronically controlled snapshot imaging measurement technology, which can quickly image the target through a single exposure. It has the advantages of fast measurement speed, strong site adaptability and portable equipment, and shows great application potential in target RCS near-field imaging measurement.

[0003] However, the huge number of array element channels greatly increases the complexity of high-resolution imaging MIMO radar systems. Traditional measurement and calibration technologies are difficult to meet the needs of high-precision measurements with a large dynamic range in complex environments, which seriously restricts the performance advantages of MIMO radars. In actual engineering applications, affected by environmental factors that change over time, the amplitude and phase of the data measured by each array element at different times are not completely coherent, resulting in a serious deterioration in the near-field imaging performance of MIMO radars. Especially in outdoor measurement environments, strong gusts can cause micro-motion of the MIMO array. This micro-motion effect will introduce random phase modulation in the echo signals of each array element of the MIMO radar system, resulting in paired echoes in the MIMO radar imaging results, thereby causing the radar image of the measured target to be distorted, which seriously affects the subsequent analysis and evaluation of the target scattering characteristics. In addition, the impact of this time-varying interference is more serious for millimeter-wave MIMO radars with shorter wavelengths.

[0004] The prior art related to the present invention is analyzed as follows:

[0005] Prior art 1: The invention patent with application number 202410646460.5 discloses "A millimeter wave radar MIMO array calibration method based on a large-size flat plate calibration body"

[0006] Technical idea: First, the millimeter-wave radar array is aligned with the center of the large-size flat panel, and the radar array plane is ensured to be parallel to the large-size flat panel; then, based on the LFMCW MIMO radar system, a MIMO radar echo intermediate frequency signal model is established; then, inherent errors such as frequency difference, phase difference and amplitude difference that exist in practice are introduced into the echo signal model; the error parameters between the channels are measured and calculated; finally, in the actual application of the radar, signal processing and other methods are used to compensate and calibrate the echo using the obtained error parameters, so that the calibrated echo signal meets the conditions for coherent synthesis.

[0007] Disadvantages of prior art 1:

[0008] This method is to obtain the calibration coefficient by measuring a large-sized flat plate calibration body in advance, and then use the calibration coefficient to calibrate the subsequent target measurement value. However, the scattering characteristics of the large-sized flat plate calibration body are very sensitive to changes in azimuth, pitch and dual-station angle. When the radar array is difficult to completely align with the center of the plate during the calibration measurement, it will cause a large error in solving the calibration coefficient, thereby affecting the calibration measurement accuracy of the target; in addition, in the field measurement environment, the array micro-motion effect caused by external factors such as strong winds is instantaneous, and it is difficult to use the calibration coefficient solved in advance to achieve effective calibration of the measured target measurement value. Therefore, this calibration method may fail in a complex field measurement environment.

[0009] Prior art 2: The invention patent with application number 202410118359.2 discloses "A MIMO stepped frequency radar channel self-calibration method"

[0010] Technical idea: First, control the MIMO radar system to switch to the calibration state and transmit the calibration signal at the same time; then, based on the system in the calibration state, receive N calibration signals through the radar's N receivers; control the MIMO radar system to switch to the transmission state and transmit M stepped frequency signals at the same time; set the ideal point target and receive the target's echo signal; use the received N calibration signals and the target's echo signal, and obtain the frequency-calibrated signal through conjugate multiplication; finally, use the signal after matched filtering to calibrate the delay of different transceiver channels through peak search and alignment operations to complete the system's stepped frequency MIMO radar channel self-calibration.

[0011] Disadvantages of the second prior art:

[0012] This method requires a separate system calibration measurement and processing module to be set up in the MIMO radar system, which increases the complexity of the system's software and hardware control. Secondly, this method obtains the calibration coefficient by setting an ideal point target in advance, and then uses the calibration coefficient to realize the system's stepped frequency MIMO radar channel self-calibration. In actual measurements, the scattered echoes generated by time-varying interference factors are not ideal point targets. Therefore, this method is also not suitable for MIMO radar system calibration under time-varying interference environments. Summary of the invention

[0013] The purpose of the present invention is to provide a MIMO radar near-field precision imaging measurement and calibration method in a time-varying interference environment, which solves the problem that the MIMO radar in actual engineering applications is affected by environmental factors that vary with time and produces paired echoes, resulting in serious deterioration of imaging performance. By simultaneously measuring the calibration body and the target to be measured remotely, the parameterized model characterization technology is used to accurately extract the scattered echoes of the calibration body, and the amplitude and phase calibration coefficients are solved channel by channel and frequency point by frequency point, so as to realize the MIMO radar near-field imaging calibration of the target to be measured.

[0014] To achieve the above object, the present invention provides a MIMO radar near-field precision imaging measurement and calibration method in a time-varying interference environment, comprising the following steps:

[0015] S1. The measured target and the calibration object are measured at different locations at the same time;

[0016] S2, calibration volume scattering echo extraction;

[0017] S3, construction of theoretical value of calibration volume scattering function;

[0018] S4, solving the MIMO array imaging calibration coefficients;

[0019] S5. Amplitude and phase calibration and imaging processing of the echo signal of the measured target.

[0020] Preferably, the specific process of step S1 is:

[0021] The target to be measured and the calibration object are placed at different radial positions in the same measurement scene, and MIMO radar near-field imaging measurements are performed under simultaneous remote conditions to obtain MIMO radar near-field imaging measurement values ​​of scattered echoes of the entire scene of the target to be measured and the calibration object.

[0022] Preferably, in step S1, the radial distance interval between the placement positions of the measured target and the calibration body in the measurement scene is greater than the radial resolution unit of the radar signal, and the calibration body and the measured target do not generate coupled scattering.

[0023] Preferably, in step S1, the MIMO radar near-field imaging measurement satisfies the following geometric relationship:

[0024] Assume that the number of transmitting elements in the array is M, and the number of receiving elements is N; take the reference center of the measured target as the origin, the lateral distance as the x-axis, and the radial distance as the y-axis to establish a rectangular coordinate system xOy; the distance from the reference center of the measured target to the center of the MIMO array is R0, and the radial distances from the mth transmitting element and the nth receiving element to a point P(x,y) on the target are R Tm and R Rn , the bistatic angle formed by this pair of transmitting and receiving antennas and the coordinate origin is 2α;

[0025] The stepped frequency radar pulse signal transmitted by the mth transmitting element of the MIMO array is expressed as:

[0026]

[0027] Where u(t) is a rectangular pulse, T r is the pulse repetition period, K is the number of pulses, f k is the carrier frequency of the kth pulse, is an imaginary unit;

[0028] The electromagnetic wave emitted by the mth transmitting array element irradiates the target to be measured, and is received by the nth receiving array element after being scattered by the target. The propagation delay of the electromagnetic wave on this path is:

[0029]

[0030] Where c is the propagation speed of electromagnetic waves;

[0031] The k-th pulse with propagation delay τ0=2R0 / c is used as the reference signal of the n-th receiving element of the MIMO radar, then:

[0032]

[0033] The frequency domain data expression of the echo signal is obtained by conjugating the received signal and the reference signal:

[0034]

[0035] In the formula, is the target scattering function;

[0036] For extended targets, the total scattering field of the measured target received by each group of MIMO radar transceiver channels is the coherent sum of the scattering fields generated by each local scattering center, that is:

[0037]

[0038] Where Γ(x, y) is the two-dimensional scattering distribution function of the target, and D is the target area;

[0039] In the presence of time-varying interference factors, the echo signal is rewritten as:

[0040]

[0041] In the formula, ΔG(f k ,t) is the amplitude error in the target echo signal caused by the time-varying interference factor, ΔR Tm (t) and ΔR Rn (t) is the phase term error in the target echo signal;

[0042] According to formula (6), the amplitude and phase errors caused by time-varying interference factors in the measurement environment are uniformly expressed as:

[0043]

[0044] Preferably, the specific process of step S2 is:

[0045] The full-scene scattered echo measured in step S1 is subjected to preliminary two-dimensional imaging processing by MIMO radar, and the two-dimensional position parameters of the calibration body in the preprocessed two-dimensional image are obtained based on the subspace spectrum estimation method, wherein the subspace spectrum estimation method adopts the multi-signal classification MUSIC method or the rotation-invariant signal parameter estimation ESPRIT method; then, the parameterized model characterization method is used to extract the scattered echo data domain measurement values ​​of the calibration body channel by channel and frequency point by frequency point.

[0046] Preferably, the specific process of step S3 is:

[0047] According to the scattering characteristics of the calibration body itself and the position relationship of the MIMO radar array elements, the theoretical value of the channel-by-channel broadband scattering function of the calibration body is established by using analytical or numerical methods.

[0048] Preferably, the specific process of step S4 is:

[0049] According to the calibration volume scattering echo measurement value extracted from the measured data in step S3 and the calibration volume scattering function theoretical value established in step S4, the MIMO array imaging calibration coefficient is solved channel by channel and frequency by frequency under the MIMO radar near-field imaging measurement condition.

[0050] Preferably, the specific process of step S5 is:

[0051] Using the channel-by-channel and frequency-by-frequency MIMO array imaging calibration coefficients solved in step S4, the echo signal measurement value of the measured target is compensated, and the MIMO radar near-field imaging of the measured target is processed using a filter-back projection (FBP) imaging algorithm;

[0052] Among them, the MIMO radar two-dimensional image reconstruction formula is expressed as:

[0053]

[0054] Preferably, in step S5, the process of processing the MIMO radar near-field imaging of the target using the filtering-back projection FBP algorithm specifically includes the following steps:

[0055] S51, frequency domain data collected by each transceiver channel of MIMO radar mn (f k ) is inverse Fourier transformed to obtain a one-dimensional high-resolution range image P for each channel mn (l);

[0056] S52, mesh the imaging area and calculate the integral path L at the image reconstruction position (x, y) mn (x, y), and the one-dimensional high-resolution distance image P m ' n (l) Perform phase compensation processing:

[0057]

[0058] In the formula, is the reconstructed value of the target scattering distribution function corresponding to the transceiver channel composed of the mth transmitting and nth receiving antennas;

[0059] S53, repeat the above steps until all the imaging area grid positions and MIMO radar transceiver channels are traversed, and finally coherent summation is performed to obtain the MIMO radar image reconstruction result:

[0060]

[0061] In the formula, Reconstruct the two-dimensional scattering distribution function of the target being measured.

[0062] Therefore, the present invention adopts the above-mentioned MIMO radar near-field precision imaging measurement and calibration method under a time-varying interference environment, and the beneficial effects are as follows:

[0063] Compared with the prior art, the method proposed in the present invention takes into account the influence of time-varying factors in the actual measurement environment on the target measurement. By simultaneously measuring the calibration object and the target to be measured remotely, and solving the amplitude and phase calibration coefficients channel by channel and frequency point by frequency point, the MIMO radar near-field imaging calibration of the target to be measured is realized. This can eliminate the influence of time-varying interference factors in the measurement environment on the imaging measurement results to a certain extent, and improve the accuracy of MIMO radar near-field imaging measurement.

[0064] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1It is a schematic diagram of the geometric relationship of MIMO radar near-field imaging measurement in an embodiment of a MIMO radar near-field precision imaging measurement and calibration method under a time-varying interference environment of the present invention;

[0066] Figure 2 It is an overall flow chart of an embodiment of a MIMO radar near-field precision imaging measurement and calibration method in a time-varying interference environment of the present invention;

[0067] Figure 3 It is a schematic diagram of placement and measurement of targets and calibration bodies in an outfield measurement of an embodiment of a MIMO radar near-field precision imaging measurement and calibration method under a time-varying interference environment of the present invention;

[0068] Figure 4 It is the MIMO radar imaging result before calibration when the wind force level of the measurement environment is level 5 in an embodiment of a MIMO radar near-field precision imaging measurement and calibration method under a time-varying interference environment of the present invention;

[0069] Figure 5 The invention is a method for measuring and calibrating near-field precision imaging of a MIMO radar in a time-varying interference environment. Figure 4 The measurement result is the imaging result after calibration using the method proposed in the present invention. DETAILED DESCRIPTION

[0070] The technical solution of the present invention is further described below through the accompanying drawings and embodiments.

[0071] Unless otherwise defined, technical or scientific terms used in the present invention shall have the common meanings understood by one having ordinary skills in the field to which the present invention belongs.

[0072] like Figure 2 As shown, a MIMO radar near-field precision imaging measurement and calibration method in a time-varying interference environment includes the following steps:

[0073] S1. The target to be measured and the calibration object are measured at different locations at the same time. The specific process is as follows:

[0074] Place the target to be measured and the calibration object at different radial positions in the same measurement scene. Note that the radial distance between the target to be measured and the calibration object in the measurement scene must be greater than the radial resolution unit of the radar signal, and the calibration object and the target to be measured will not produce coupled scattering.

[0075] Perform MIMO radar near-field imaging measurements under simultaneous remote conditions to obtain MIMO radar near-field imaging measurement values ​​of scattered echoes of the measured target and the calibration body in the entire scene. Figure 1 As shown, the MIMO radar near-field imaging measurement satisfies the following geometric relationship:

[0076] Assume that the number of transmitting elements in the array is M, and the number of receiving elements is N; take the reference center of the measured target as the origin, the lateral distance as the x-axis, and the radial distance as the y-axis to establish a rectangular coordinate system xOy; the distance from the reference center of the measured target to the center of the MIMO array is R0, and the radial distances from the mth transmitting element and the nth receiving element to a point P(x,y) on the target are R Tm and R Rn The bistatic angle formed by the pair of transmitting and receiving antennas consisting of the mth transmitting array element and the nth receiving array element and the coordinate origin is 2α.

[0077] The stepped frequency radar pulse signal transmitted by the mth transmitting element of the MIMO array can be expressed as:

[0078]

[0079] Where u(t) is a rectangular pulse, T r is the pulse repetition period, K is the number of pulses, f k is the carrier frequency of the kth pulse, is an imaginary unit;

[0080] The electromagnetic wave emitted by the mth transmitting array element irradiates the target to be measured, and is received by the nth receiving array element after being scattered by the target. The propagation delay of the electromagnetic wave on this path is:

[0081]

[0082] Where c is the propagation speed of electromagnetic waves.

[0083] The k-th pulse with propagation delay τ0=2R0 / c is used as the reference signal of the n-th receiving element of the MIMO radar, then:

[0084]

[0085] By conjugating the received signal and the reference signal, the frequency domain data expression of the echo signal can be obtained as follows:

[0086]

[0087] In the formula, is the target scattering function;

[0088] For extended targets, the total scattering field of the measured target received by each group of MIMO radar transceiver channels is the coherent sum of the scattering fields generated by each local scattering center, that is:

[0089]

[0090] Where Γ(x, y) is the two-dimensional scattering distribution function of the target, and D is the target area;

[0091] In the presence of time-varying interference factors, the echo signal can be rewritten as:

[0092]

[0093] In the formula, ΔG(f k ,t) is the amplitude error in the target echo signal caused by the time-varying interference factor, ΔR Tm (t) and ΔR Rn (t) is the phase term error in the target echo signal.

[0094] According to formula (6), the amplitude and phase errors caused by time-varying interference factors in the measurement environment can be written uniformly as:

[0095]

[0096] S2. Calibration of volume scattering echo extraction. The specific process is as follows:

[0097] The MIMO radar preliminary two-dimensional imaging processing is performed on the full-scene scattered echo measured in step S1, and the two-dimensional position parameters of the calibration body in the pre-processed two-dimensional image are obtained based on the subspace spectrum estimation method, wherein the subspace spectrum estimation method adopts the multiple signal classification MUSIC method or the rotation invariant signal parameter estimation ESPRIT method. The specific method can refer to the method recorded in the article "Multiple Emitter Location and Signal Parameter Estimation" published by Schmidt et al. in 1979 and the article "ESPRIT—Estimation of Signal Parameters via Rotational Invariance Techniques" published by Roy et al. in 1989, which will not be repeated here. Then, the parameterized model characterization method is used to extract the scattered echo data domain measurement value of the calibration body channel by channel and frequency point by frequency point.

[0098] S3. Construction of the theoretical value of the calibration volume scattering function. The specific process is as follows:

[0099] According to the scattering characteristics of the calibration body itself and the position relationship of the MIMO radar array elements, the theoretical value of the channel-by-channel broadband scattering function of the calibration body is established by using analytical or numerical methods.

[0100] S4. Solve the MIMO array imaging calibration coefficients. The specific process is as follows:

[0101] According to the calibration volume scattering echo measurement value extracted from the measured data in step S3 and the calibration volume scattering function theoretical value established in step S4, the MIMO array imaging calibration coefficient is solved channel by channel and frequency by frequency under the MIMO radar near-field imaging measurement condition.

[0102] S5, amplitude and phase calibration and imaging processing of the target echo signal, the specific process is as follows:

[0103] The channel-by-channel and frequency-by-frequency MIMO array imaging calibration coefficients solved in step S4 are used to compensate the echo signal measurement value of the measured target. Finally, the filtering-back projection FBP imaging algorithm is used to process the MIMO radar near-field imaging of the measured target.

[0104] Among them, the MIMO radar two-dimensional image reconstruction formula can be expressed as:

[0105]

[0106] The FBP algorithm can directly perform phase compensation and coherent focusing processing on polar coordinate format data to reconstruct the target image. It is not limited by the MIMO array configuration and imaging distance and is suitable for MIMO radar near-field precision imaging measurement.

[0107] The MIMO radar near-field imaging of the target is processed using the filter-back projection FBP algorithm (MIMO radar image reconstruction process), which specifically includes the following steps:

[0108] S51, frequency domain data collected by each transceiver channel of MIMO radar mn (f k ) is inverse Fourier transformed to obtain a one-dimensional high-resolution range image P for each channel mn (l);

[0109] S52, mesh the imaging area and calculate the integral path L at the image reconstruction position (x, y) mn (x, y), and the one-dimensional high-resolution distance image P m ' n (l) Perform phase compensation processing:

[0110]

[0111] In the formula, is the reconstructed value of the target scattering distribution function corresponding to the transceiver channel composed of the mth transmitting and nth receiving antennas;

[0112] S53, repeat the above steps until all the imaging area grid positions and MIMO radar transceiver channels are traversed, and finally coherent summation is performed to obtain the MIMO radar image reconstruction result:

[0113]

[0114] In the formula, Reconstruct the two-dimensional scattering distribution function of the target being measured.

[0115] Embodiment 1

[0116] This embodiment uses MIMO radar field measurement data to verify and illustrate the proposed method. The installation method of MIMO radar, calibration object and target in the actual measurement scene is as follows: Figure 3 The measurement parameters are shown in Table 1.

[0117] Table 1 MIMO radar field measurement parameters

[0118] Measurement parameters Parameter Value Radar frequency / GHz 12-18 Frequency step / MHz 2 Measuring distance / m 35 MIMO radar antenna height / m 9.11 Target measurement ground rubbing angle / (°) 15 Polarization HH polarization Measuring ambient wind speed level Gust 5

[0119] The results of direct imaging using MIMO radar target measurement data are as follows: Figure 4 As shown, it can be seen that when there is a strong wind, paired echoes are generated due to the array micro-motion modulation, which seriously deteriorates the image quality of the imaging results using the traditional method, and the RCS dynamic range is only about 35dB.

[0120] The measurement results after calibration using the method proposed by the present invention are as follows: Figure 5 As shown, it can be seen that the method provided by the present invention can effectively eliminate the influence of time-varying interference factors such as strong wind in the field measurement environment. The RCS dynamic range of the calibrated image can reach 45dB, achieving good MIMO radar imaging calibration.

[0121] Therefore, the present invention adopts the above-mentioned MIMO radar near-field precision imaging measurement and calibration method in a time-varying interference environment. In the target near-field diagnostic imaging measurement using MIMO radar, it can eliminate the influence of time-varying interference factors in the measurement environment on the imaging measurement results to a certain extent, thereby improving the accuracy of MIMO radar near-field imaging measurement.

[0122] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that they can still modify or replace the technical solution of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solution to deviate from the spirit and scope of the technical solution of the present invention.

Claims

1. A MIMO radar near-field precision imaging measurement and calibration method under time-varying interference environment, characterized in that: The following steps are involved: S1. The measured target and the calibration object are measured at different locations at the same time; S2, calibration volume scattering echo extraction; S3, construction of theoretical value of calibration volume scattering function; S4, solving the MIMO array imaging calibration coefficients; S5, amplitude and phase calibration and imaging processing of the echo signal of the measured target; The specific process of step S1 is: The target to be measured and the calibration body are placed at different radial positions in the same measurement scene, and MIMO radar near-field imaging measurements are performed under simultaneous remote conditions to obtain MIMO radar near-field imaging measurement values ​​of scattered echoes of the target to be measured and the calibration body in the entire scene; In step S1, the MIMO radar near-field imaging measurement satisfies the following geometric relationship: Assume that the number of transmitting elements in the array is M , the number of receiving array elements is N ; Taking the reference center of the measured target as the origin, the lateral distance is Axis, radial distance is Axis, establish rectangular coordinate system ; The distance from the reference center of the measured target to the center of the MIMO array is , No. The transmitting element and receiving array element to a point on the target The radial distances are and , the bistatic angle formed by this pair of transmitting and receiving antennas and the coordinate origin is ; MIMO Array The stepped frequency radar pulse signal emitted by a transmitting array element is expressed as: （1） In the formula, is a rectangular pulse, is the pulse repetition period, K is the number of pulses, For the The carrier frequency of the pulse, is an imaginary unit; No. The electromagnetic waves emitted by the first transmitting element hit the target and are scattered by the first element. The receiving array element receives the electromagnetic wave, and the propagation delay of the path is: （2） In the formula, c is the propagation speed of electromagnetic waves; Delay the propagation No. The pulse is used as the first The reference signal of the receiving array element is: （3） The frequency domain data expression of the echo signal is obtained by conjugating the received signal and the reference signal: （4） In the formula, is the target scattering function; For extended targets, the total scattering field of the measured target received by each group of MIMO radar transceiver channels is the coherent sum of the scattering fields generated by each local scattering center, that is: （5） In the formula, is the two-dimensional scattering distribution function of the target, D is the target area; In the presence of time-varying interference factors, the echo signal is rewritten as: （6） In the formula, is the amplitude error in the target echo signal caused by the time-varying interference factor, and is the phase error in the target echo signal; According to formula (6), the amplitude and phase errors caused by time-varying interference factors in the measurement environment are uniformly expressed as: （7）。 2. The method for near-field precision imaging measurement and calibration of MIMO radar in a time-varying interference environment according to claim 1 is characterized in that: In step S1, the distance interval in the radial direction between the placement positions of the measured target and the calibration body in the measurement scene is greater than the radial resolution unit of the radar signal, and the calibration body and the measured target do not generate coupled scattering.

3. The method for near-field precision imaging measurement and calibration of MIMO radar in a time-varying interference environment according to claim 2 is characterized in that: The specific process of step S2 is: The full-scene scattered echo measured in step S1 is subjected to preliminary two-dimensional imaging processing by MIMO radar, and the two-dimensional position parameters of the calibration body in the preprocessed two-dimensional image are obtained based on the subspace spectrum estimation method, wherein the subspace spectrum estimation method adopts the multi-signal classification MUSIC method or the rotation-invariant signal parameter estimation ESPRIT method; then, the parameterized model characterization method is used to extract the scattered echo data domain measurement values ​​of the calibration body channel by channel and frequency point by frequency point.

4. The method for near-field precision imaging measurement and calibration of MIMO radar in a time-varying interference environment according to claim 3 is characterized in that: The specific process of step S3 is: According to the scattering characteristics of the calibration body itself and the position relationship of the MIMO radar array elements, the theoretical value of the channel-by-channel broadband scattering function of the calibration body is established by using analytical or numerical methods.

5. The method for near-field precision imaging measurement and calibration of MIMO radar in a time-varying interference environment according to claim 4 is characterized in that: The specific process of step S4 is: According to the calibration volume scattering echo measurement value extracted from the measured data in step S3 and the calibration volume scattering function theoretical value established in step S4, the MIMO array imaging calibration coefficient is solved channel by channel and frequency by frequency under the MIMO radar near-field imaging measurement condition.

6. The method for near-field precision imaging measurement and calibration of MIMO radar in a time-varying interference environment according to claim 5 is characterized in that: The specific process of step S5 is: The channel-by-channel and frequency-by-frequency MIMO array imaging calibration coefficients solved in step S4 are used to compensate the echo signal measurement value of the measured target, and the MIMO radar near-field imaging of the measured target is processed by using the filtering-back projection FBP imaging algorithm; Among them, the MIMO radar two-dimensional image reconstruction formula is expressed as: （8）。 7. The method for near-field precision imaging measurement and calibration of MIMO radar in a time-varying interference environment according to claim 6 is characterized in that: In step S5, the process of processing the MIMO radar near-field imaging of the target by using the filtering-back projection FBP algorithm specifically includes the following steps: S51, frequency domain data collected from each transceiver channel of MIMO radar Perform inverse Fourier transform to obtain a one-dimensional high-resolution range image for each channel ; S52, gridding the imaging area and calculating the image reconstruction position The integral path at , and convert the one-dimensional high-resolution distance image Perform phase compensation processing: （9） In the formula, For the corresponding The first launch The reconstructed value of the target scattering distribution function of the transmit-receive channel composed of receiving antennas; S53, repeat the above steps until all the imaging area grid positions and MIMO radar transceiver channels are traversed, and finally coherent summation is performed to obtain the MIMO radar image reconstruction result: （10） In the formula, Reconstruct the two-dimensional scattering distribution function of the target being measured.

Images