Two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement

Abstract

The present invention discloses a two-dimensional processing method for suppressing specific scatterer echoes in radar cross-section measurements, comprising the following steps: target filtered back-projection two-dimensional imaging, detection and identification of specific scatterer position parameters; two-dimensional detection and region segmentation of specific scatterers; target scattering judgment within the specific scatterer region; reconstruction of specific scatterer echo data; vector subtraction processing of specific scatterer echo data; and acquisition of target scattered echo data that varies with frequency and azimuth, thereby accurately extracting and suppressing the specific scatterer echo data. In radar cross-section (RCS) measurements of target entire machines or target components, the present invention employs the above-mentioned two-dimensional processing method for suppressing specific scatterer echoes in radar cross-section measurements. Without the aid of a target geometric model, the method can effectively suppress the echo signals of specific scatterers, such as target supports and carriers, that are mixed in with the target scattered echoes, thereby reducing the influence of background clutter and improving RCS measurement accuracy.

Description

Technical Field

[0001] The present invention relates to the field of communication and radar technology, and in particular to a two-dimensional processing method for suppressing echoes of specific scatterers in radar cross-section measurement. Background Art

[0002] Accurate measurement of radar cross section (RCS) is an important process for achieving the low-scattering shape design and maintenance of low-observable targets. In microwave darkroom and outdoor static measurements, the target is generally mounted on a low-scattering bracket for stable support. During the measurement process, the RCS measurement radar is fixed, and the target is driven by a turntable to rotate in azimuth. The measurement radar obtains the scattered echoes of the target at different azimuth angles. After background cancellation and RCS calibration processing, the full-range RCS measurement data of the target is obtained. The typical geometric relationship of target RCS outdoor measurement is as follows: Figure 1 shown.

[0003] The echo signal received by the actual radar system is a complex signal and includes the influence of background clutter and noise in the test field. The radar echo signals of the measurement target and the calibration object can be expressed as:

[0004] M T (f) = S T (f)+B T (f)+N T (1)

[0005] and

[0006] M C (f) = S C (f)+B C (f)+N C (2)

[0007] Where M T (f) and M C (f) respectively represent the echo signals received by the radar when measuring the target and the standard; S T (f) represents the real echo of the target; S C (f) represents the real echo of the calibration body; B T (f) and B C (f) respectively represent the background echo when measuring the target and the standard; N T and N C They represent the noise impact when measuring the target and the standard respectively. The above echo signals are all complex phasors.

[0008] In target RCS measurement engineering applications, the signal-to-noise ratio of echo signal measurement can generally be improved by increasing the transmit power, adopting a ground-level test field configuration, and using coherent accumulation processing for the received signal, thereby ignoring the impact of noise on the target measurement signal. The echo measurement signal is approximately satisfied by the following formula:

[0009] M T (f) = S T (f)+B T (f) (3)

[0010] and

[0011] M C (f) = S C (f)+B C (f) (4)

[0012] In order to improve the target RCS measurement accuracy, the background phase subtraction technology is generally used in the calibration process. The calibration equation of the target scattering function is:

[0013]

[0014] Where, is the target scattering function (also known as complex RCS, which is a quantity that needs to be measured and calibrated), is the scattering function of the calibration body, which is a known quantity that can be obtained through precise theoretical calculation.

[0015] Therefore, the target RCS measurement calibration equation with background cancellation processing is:

[0016]

[0017] In most indoor RCS test sites, the target and the standard are measured on the same bracket at the same distance. In this case, the background echo B T (f) and the background echo B when measuring the standard C (f) are the same, so we have:

[0018]

[0019] In actual RCS measurement engineering applications, the support structures used at different test sites vary. Some test sites use fixed low-scatter supports with an azimuth turntable mounted on top to drive the target in azimuth rotation. In this case, the support's scattered echo forms a zero-Doppler echo signal that remains constant with azimuth. In other test sites, the low-scatter support is mounted on a large turntable, and the target is mounted on the support. In this case, both the support and the target are driven by the turntable to complete azimuth rotation measurement. The support's scattered echo forms an echo signal with amplitude and phase varying with azimuth rotation. Furthermore, the low-scatter carrier used for target component measurement is driven simultaneously with the target by the turntable during the measurement process, completing a 360° azimuth rotation measurement. In this case, the scattered echo from the low-scatter carrier also forms an echo signal that varies with azimuth rotation. These scattering structures, whether part of the target component or not, but located in the target area and contributing to the scattered measurement echo, are referred to as specific scatterers. Examples include the target support used in whole-unit target measurement and the carrier used in target component measurement.

[0020] Therefore, in the RCS measurement of the target whole machine or target component, how to accurately measure the scattered echoes generated by structures such as the target bracket and carrier, and then suppress the echoes of specific scatterers (target bracket, carrier) mixed into the target scattered echo, is the key to achieving accurate calibration measurement of the target RCS.

[0021] (1) The prior art-1 related to the present invention is analyzed as follows:

[0022] Technical solution of existing technology-1: Aiming at the extraction and elimination of zero-Doppler clutter signals, auxiliary measurement devices and signal processing methods are used to achieve the extraction and elimination of zero-Doppler clutter such as fixed background in the RCS test field. The main methods include:

[0023] (a) Design a low-scatter end cap to assist in measurement. When measuring background, the rotating top of the bracket is "hidden" with the cap, just as when measuring targets. The measured echo is assumed to be primarily composed of fixed background clutter. For example, Guidi et al. proposed several low-scatter end caps with different shapes in their 2002 paper "NRTF's 14-Foot Pylon."

[0024] (b) Using a background auxiliary measurement device with a constant scattering amplitude, background extraction and subsequent background cancellation processing are completed through auxiliary measurement and signal processing. For example, Morgan et al. proposed using an object translated on a bracket as a background auxiliary measurement body in the paper "RCS Target Support Background Determination Using a Translating Test Body" in 1996; Muth et al. proposed using an eccentric cylinder as a background auxiliary measurement body in the paper "Robust Separation of Background and Target Signals in Radar Cross Section Measurements" in 2005; Wood et al. proposed using a CAM calibration body as a background auxiliary measurement body in the paper "The CAM RCS Dual-Cal Standard" in 2003; and the invention patent with publication number CN201610237378.2 disclosed the use of a SCAM calibration body as a background auxiliary measurement body in the "Design of a device for multiple calibration and background extraction in target RCS measurement and its signal processing method".

[0025] (c) A low-scattering end cap is used as a background auxiliary measurement body, and background extraction and subsequent background cancellation processing are completed through auxiliary measurement and signal processing, including: the full-scale averaging method for background extraction proposed by Xu Xiaojian in the article "A Background and Target Signal Separation Technique For Exact RCS Measurement" in 2012; the data domain processing method based on maximum probability for background extraction and cancellation recorded in the "Maximum Probability Data Domain Processing Method for Background Extraction and Cancellation in Target RCS Measurement" disclosed in the invention patent with publication number CN201610764900.2; the time domain processing method based on maximum probability for background extraction and cancellation recorded in the "Time Domain Processing Method for Background Measurement and Extraction Based on Maximum Probability" disclosed in the invention patent with publication number CN201610764605.7; and the "Background Extraction Method Based on Joint Processing of Maximum Probability Threshold and Model Prediction" disclosed in the invention patent with publication number 201610813955.8.

[0026] The disadvantage of existing technology 1 is that it takes advantage of the fact that the fixed background does not change or changes slowly with the azimuth angle during RCS measurement to extract the zero-Doppler echo signal and perform background cancellation processing. Therefore, this type of technology can only extract and suppress zero-Doppler signals or slowly changing echo signals such as fixed background clutter, but cannot extract and suppress echo signals of specific scatterers that change with azimuth.

[0027] (2) The prior art-2 related to the present invention is analyzed as follows:

[0028] Technical solution for existing technology-2: Regarding the extraction and elimination of sliding scattering centers, Xu Xiaojian et al. proposed in their 2023 paper "Sliding Scattering Center Extraction for Streamlined Radar Targets" to use the geometric model of the target to determine the geometric shape of the component structure corresponding to a specific sliding scattering center, and predict its sine and cosine trajectories that change with azimuth in a one-dimensional high-resolution range profile (HRRP). Then, the basis pursuit method is used to sparsely characterize and reconstruct the azimuth range of the specific sliding scattering center, thereby realizing the extraction and suppression of the echo signal of the specific sliding scattering center.

[0029] Disadvantages of Existing Technology 2: Because it requires a geometric model of the target to determine the trajectory of a specific scattering center as it changes with azimuth, this method relies on a precise geometric model of the target. However, in actual RCS measurements, it is difficult to accurately capture the geometric structure of specific scatterers, such as the target bracket used for whole-unit measurement and the carrier used for target component measurement. Therefore, this method cannot extract and suppress the echoes of these specific scatterers. Furthermore, the use of basis pursuit to sparsely represent and reconstruct the echo signals of the scattering centers results in a high computational load. Summary of the Invention

[0030] The purpose of the present invention is to provide a two-dimensional processing method for suppressing specific scatterer echoes in radar cross-section measurements. The technical problem to be solved is that existing methods for suppressing scattering center echo signals in RCS measurements can only extract and suppress zero-Doppler clutter that remains constant with azimuth, or, with the assistance of a precise target geometric model, extract and suppress sliding scattering centers that vary with azimuth. However, in actual RCS measurements, specific scatterers, such as target supports used in whole-unit target measurements and carriers used in target component measurements, vary with azimuth, and the precise geometric structures of these scatterers are difficult to obtain. Therefore, existing methods are unable to suppress these specific scatterers. The present invention is proposed to address this problem.

[0031] To achieve the above object, the present invention provides a two-dimensional processing method for suppressing echoes of specific scatterers in radar cross section measurement, comprising the following steps:

[0032] S1, target filtered back projection two-dimensional imaging;

[0033] S2, two-dimensional detection and region segmentation of specific scatterers;

[0034] S3, target scattering judgment within a specific scatterer area;

[0035] S4, reconstruction of specific scatterer echo data;

[0036] S5, vector subtraction processing of specific scatterer echo data;

[0037] S6. Acquire target scattered echo data that varies with frequency and azimuth.

[0038] Preferably, the specific scatterer refers to a scattering structure located in the target area and contributing to the scattering measurement echo, including a target bracket used in target whole machine measurement and a carrier used in target component measurement.

[0039] Preferably, in step S1, the target filtered back projection two-dimensional imaging is specifically:

[0040] Perform 360° rotation measurement on the target to obtain the original measurement data of scattered echo amplitude and phase that varies with frequency and azimuth angle, and realize two-dimensional inverse synthetic aperture ISAR imaging of the target through filtered back projection;

[0041] Among them, the expression of the filtered back projection imaging algorithm is:

[0042]

[0043]

[0044] Where, P θ (L e ) is the high-resolution range image HRRP obtained by the target measurement value, Δθ is the target azimuth rotation angle, k=2π / λ is the wave number vector, L e Integrate the trajectory for target imaging.

[0045] Preferably, in step S2, the two-dimensional detection and region segmentation of the specific scatterer are specifically as follows:

[0046] In the target two-dimensional inverse synthetic aperture ISAR image, specific scatterers are detected and identified, the two-dimensional precise position parameters of the specific scatterers are determined, and the local area of ​​the specific scatterers is segmented.

[0047] Preferably, in step S3, the target scattering judgment within the specific scatterer area is specifically as follows:

[0048] According to the two-dimensional imaging characteristics of the target, it is determined whether the target scattered echo is mixed in the local imaging area of ​​the specific scatterer.

[0049] Preferably, in step S4, the specific scatterer echo data is reconstructed as follows:

[0050] If there is no target scattered echo in the local imaging area of ​​a specific scatterer, the echo data of the specific scatterer is directly reconstructed based on the two-dimensional inverse synthetic aperture ISAR image; if there is a target scattered echo in the local imaging area of ​​a specific scatterer, a parameterized model of the scattering signal in the imaging area is established.

[0051] Preferably, in step S4, if there is no target scattered echo in the local imaging area of ​​the specific scatterer, the echo data of the specific scatterer is directly reconstructed based on the two-dimensional inverse synthetic aperture ISAR image, and the specific process is as follows:

[0052] The local imaging area of ​​a specific scatterer obtained by the filtered back projection imaging algorithm is subjected to a two-dimensional fast Fourier transform (FFT) to obtain the sector-shaped wavenumber domain data. Then, resampling is performed along the sector-shaped ring to obtain the echo data of the specific scatterer. The resampling formula of the two-dimensional data along the frequency and azimuth angle is:

[0053]

[0054] and

[0055]

[0056] Where, The vertical index value corresponding to the sampling point on the fan ring or ring, subscript f i is the frequency vector, n y is the number of imaging points in the radial direction of the two-dimensional inverse synthetic aperture ISAR image, L y is the radial imaging distance, θ j is the azimuth corresponding to the sampling point, The subscript a is the horizontal index value corresponding to the sampling point on the fan ring or ring. j Indicates direction, n x is the number of imaging points of the two-dimensional inverse synthetic aperture ISAR image in the lateral direction, L x is the lateral imaging distance.

[0057] Preferably, in step S4, if there is a target scattered echo in the local imaging area of ​​the specific scatterer, a parameterized model is established for the scattered signal in the imaging area. The specific process is as follows:

[0058] Based on the complex exponential CE parameterized characterization model, the frequency domain echo signal of a specific scatterer is reconstructed. The specific method is as follows:

[0059] The CE model expression of the scattering function of a specific scatterer is written as:

[0060]

[0061] Where a i , αi and r i are the complex scattering amplitude, frequency dispersion factor and distance to the target reference center of the i-th scattering component, M is the model order, that is, the number of scattering components of the CE model, f is the radar frequency, and c is the electromagnetic wave velocity;

[0062] Assuming that the kth scattering center characterizing a specific scatterer is represented by the m1th to m2th scattering components of the CE model, the echo signal of this kth scattering center is expressed as:

[0063]

[0064] Where m1 and m2 are respectively the main lobe position boundary r of the kth scattering center in HRRP. m1 and r m2 Determined.

[0065] Preferably, in step S5, the specific scatterer echo data vector subtraction process is specifically as follows:

[0066] For the azimuth-by-azimuth frequency domain scattered echo data, a phasor subtraction process is performed between the target original measurement data and the estimated data of the specific scatterer.

[0067] Preferably, in step S6, the acquired target scattered echo measurement data that varies with frequency and azimuth is used for subsequent target imaging and scattering analysis processing.

[0068] Therefore, the present invention adopts the above-mentioned two-dimensional processing method for suppressing the echo of a specific scatterer in radar cross section measurement, and the beneficial effects are as follows:

[0069] (1) The present invention takes into account the specific scatterers in the actual target RCS measurement, which may or may not belong to the target component being measured but are located in the target area and contribute to the scattered measurement echo, such as the target bracket used in the target whole machine measurement, the carrier used for the target component measurement, etc. The echo of these specific scatterers may be fixed or change with the azimuth angle. Compared with the traditional method, the proposed method is not only applicable to the suppression of zero-Doppler echoes that are fixed with the azimuth angle, but also applicable to the suppression of scatterer echoes that change with the azimuth angle rotation.

[0070] (2) The present invention solves the problem that it is difficult to obtain the geometric model of a specific scatterer that produces complex scattered echoes that affect the measurement accuracy of the target RCS. The proposed method does not require auxiliary information of the geometric model of the specific scatterer. The two-dimensional position parameters of the target can be detected and identified in the two-dimensional inverse synthetic aperture ISAR image through inverse projection imaging, thereby realizing the echo data reconstruction and vector subtraction processing of the specific scatterer. Compared with the traditional method, the proposed method overcomes the limitation that the extraction of the specific scatterer echo must rely on the auxiliary information of the geometric model.

[0071] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 The embodiment of the two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement of the present invention is a target RCS measurement geometric relationship;

[0073] Figure 2 This is a flow chart of a two-dimensional processing method for suppressing echoes of specific scatterers in radar cross section measurement according to an embodiment of the present invention;

[0074] Figure 3 Target echo data contaminated by specific scatterer echoes according to an embodiment of a two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement of the present invention, wherein (a) is data domain echo data varying with frequency and azimuth, (b) is a one-dimensional HRRP sequence in the time domain, and (c) is a two-dimensional inverse synthetic aperture ISAR image;

[0075] Figure 4 Target echo data after specific scatterer suppression in an embodiment of a two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement of the present invention, wherein (a) is data domain echo data that varies with frequency and azimuth, (b) is a one-dimensional HRRP sequence in the time domain, and (c) is a two-dimensional inverse synthetic aperture ISAR image;

[0076] Figure 5 The present invention provides uncontaminated target echo data from an embodiment of a two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement, wherein (a) is data domain echo data that varies with frequency and azimuth, (b) is a one-dimensional HRRP sequence in the time domain, and (c) is a two-dimensional inverse synthetic aperture ISAR image. DETAILED DESCRIPTION

[0077] The technical solution of the present invention is further described below with reference to the accompanying drawings and embodiments.

[0078] Unless otherwise defined, technical or scientific terms used in the present invention shall have the same meaning as commonly understood by one of ordinary skill in the art to which the present invention belongs.

[0079] The present invention provides a two-dimensional processing method for suppressing specific scatterer echoes in radar cross-section measurement. The method uses filtered back-projection two-dimensional inverse synthetic aperture (ISAR) imaging of specific scatterer echo data in target radar cross-section measurement to extract and suppress specific scatterer echo data. The method does not require auxiliary information about the geometric model of the measured target and can extract and suppress both zero-Doppler echo signals that are invariant with azimuth and echo signals that vary with azimuth.

[0080] Among them, specific scatterers refer to scattering structures that belong to or do not belong to the target component being measured, but are located in the target area and contribute to the scattered measurement echo, such as the target bracket used in the target whole machine measurement, the carrier used for the target component measurement, etc.

[0081] Specific scatterer echo suppression refers to the suppression of echoes from specific scatterers (target brackets, carriers) that are mixed into the target scattered echo during the RCS measurement of the target whole machine or target component. Only by eliminating these stray echoes can an accurate measurement of the target RCS be obtained.

[0082] like Figure 2 As shown in FIG, a two-dimensional processing method for suppressing echoes of specific scatterers in radar cross section measurement includes the following steps:

[0083] S1, target filtering back projection two-dimensional imaging, specifically:

[0084] Perform 360° rotation measurement on the target to obtain the original measurement data of scattered echo amplitude and phase that varies with frequency and azimuth angle, and realize two-dimensional inverse synthetic aperture ISAR imaging of the target through filtered back projection;

[0085] Among them, the expression of the filtered back projection imaging algorithm is:

[0086]

[0087]

[0088] Where, P θ (L e ) is the high-resolution range image HRRP obtained by the target measurement value, Δθ is the target azimuth rotation angle, k=2π / λ is the wave number vector, L e Integrate the trajectory for target imaging.

[0089] S2. Specific scatterer two-dimensional detection and region segmentation, specifically:

[0090] In the target two-dimensional inverse synthetic aperture ISAR image, specific scatterers are detected and identified, the two-dimensional precise position parameters of the specific scatterers are determined, and the local area of ​​the specific scatterers is segmented.

[0091] S3. Target scattering judgment within a specific scatterer area, specifically:

[0092] According to the two-dimensional imaging characteristics of the target, it is determined whether the target scattered echo is mixed in the local imaging area of ​​the specific scatterer.

[0093] S4. Reconstruction of specific scatterer echo data, specifically:

[0094] If there is no target scattered echo within the local imaging area of ​​a specific scatterer, the echo data of the specific scatterer is directly reconstructed based on the 2D inverse synthetic aperture ISAR image. The specific process is as follows:

[0095] The local imaging area of ​​a specific scatterer obtained by the filtered back projection imaging algorithm is subjected to a two-dimensional fast Fourier transform (FFT) to obtain the sector-shaped wavenumber domain data. Then, resampling is performed along the sector-shaped ring to obtain the echo data of the specific scatterer. The resampling formula of the two-dimensional data along the frequency and azimuth angle is:

[0096]

[0097] and

[0098]

[0099] Where, The vertical index value corresponding to the sampling point on the fan ring or ring, subscript f i is the frequency vector, n y is the number of imaging points in the radial direction of the two-dimensional inverse synthetic aperture ISAR image, L y is the radial imaging distance, θ j is the azimuth corresponding to the sampling point, The subscript a is the horizontal index value corresponding to the sampling point on the fan ring or ring. j Indicates direction, n x is the number of imaging points of the two-dimensional inverse synthetic aperture ISAR image in the lateral direction, L x is the lateral imaging distance.

[0100] If there is a target scattered echo in the local imaging area of ​​a specific scatterer, a parameterized model of the scattered signal in the imaging area is established to reconstruct the frequency domain echo signal of the specific scatterer. The specific process is as follows:

[0101] Based on the complex exponential CE parameterized characterization model, the frequency domain echo signal of a specific scatterer is reconstructed. The specific method is as follows:

[0102] The CE model expression of the scattering function of a specific scatterer is written as:

[0103]

[0104] Where a i , α i and r i are the complex scattering amplitude, frequency dispersion factor and distance to the target reference center of the i-th scattering component, M is the model order, that is, the number of scattering components of the CE model, f is the radar frequency, and c is the electromagnetic wave velocity;

[0105] Assuming that the kth scattering center characterizing a specific scatterer can be represented by the m1th to m2th scattering components of the CE model, the echo signal of this kth scattering center is expressed as:

[0106]

[0107] Where m1 and m2 are respectively the main lobe position boundary r of the kth scattering center in HRRP. m1 and r m2 Determined.

[0108] S5. Vector subtraction processing of specific scatterer echo data, specifically:

[0109] For the azimuth-by-azimuth frequency domain scattered echo data, a phasor subtraction process is performed between the target original measurement data and the estimated data of the specific scatterer.

[0110] S6. Acquire target scattered echo data that varies with frequency and azimuth for subsequent target imaging, scattering analysis, and other processing.

[0111] The technical effects of the present invention can be further illustrated by the following examples.

[0112] The data used in this embodiment is the aircraft target simulation data obtained by moment method electromagnetic calculation. The frequency sampling is 4.5~5.5GHz, the step frequency is 5MHz, the azimuth angle sampling is -180°~180°, and the step angle is 0.06°. Figure 2 The flowchart of the one-dimensional processing method for suppressing the echo of a specific scatterer is shown to process the simulation data.

[0113] like Figure 3 (b) It can be seen that the three sine and cosine curves with stronger amplitudes are the trajectories of the radial distance change of the scattering center caused by the echo of a specific scatterer. Figure 3 (c) It can be seen that the echo of a specific scatterer appears as a strong scattering center in the two-dimensional image, which seriously affects the target RCS measurement results.

[0114] like Figure 4 The method proposed by the present invention is shown to suppress Figure 3 The processing results of the specific scatterer echo show that the echo of the specific scatterer is significantly suppressed. Figure 5Compared with the echo data of the uncontaminated target being measured, the two have good consistency.

[0115] Therefore, the present invention adopts the two-dimensional processing method for suppressing the echo of specific scatterers in the above-mentioned radar scattering cross-section measurement, which can effectively suppress the echo of specific scatterers (target brackets, carriers) mixed into the target scattered echo in the RCS measurement of the target whole machine or target component, thereby improving the measurement accuracy of the target RCS.

[0116] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit the same. 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 solutions of the present invention with equivalents, and these modifications or equivalent replacements cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A two-dimensional processing method for suppressing echoes from specific scatterers in radar cross section measurement, characterized in that: The following steps are involved: S1, target filtered back projection two-dimensional imaging; S2, two-dimensional detection and region segmentation of specific scatterers; S3, target scattering judgment within a specific scatterer area; S4, reconstruction of specific scatterer echo data; S5, vector subtraction processing of specific scatterer echo data; S6. Acquire target scattered echo data that varies with frequency and azimuth; The specific scatterer refers to a scattering structure located in the target area and contributing to the scattering measurement echo, including a target bracket used in target whole machine measurement and a carrier used in target component measurement; In step S1, the target filtered back-projection two-dimensional imaging is specifically as follows: Perform 360° rotation measurement on the target to obtain the original measurement data of scattered echo amplitude and phase that varies with frequency and azimuth angle, and realize two-dimensional inverse synthetic aperture ISAR imaging of the target through filtered back projection; Among them, the expression of the filtered back projection imaging algorithm is: Where, P θ (L e ) is the high-resolution range image HRRP obtained by the target measurement value, Δθ is the target azimuth rotation angle, k=2π / λ is the wave number vector, L e Integrate the trajectory for target imaging.

2. The two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement according to claim 1, characterized in that: In step S2, the two-dimensional detection and region segmentation of the specific scatterer are specifically as follows: In the target two-dimensional inverse synthetic aperture ISAR image, specific scatterers are detected and identified, the two-dimensional precise position parameters of the specific scatterers are determined, and the local area of ​​the specific scatterers is segmented.

3. The two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement according to claim 2, characterized in that: In step S3, the target scattering judgment in the specific scatterer area is specifically as follows: According to the two-dimensional imaging characteristics of the target, it is determined whether the target scattered echo is mixed in the local imaging area of ​​the specific scatterer.

4. The two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement according to claim 3, characterized in that: In step S4, the specific scatterer echo data is reconstructed as follows: If there is no target scattered echo in the local imaging area of ​​a specific scatterer, the echo data of the specific scatterer is directly reconstructed based on the two-dimensional inverse synthetic aperture ISAR image; if there is a target scattered echo in the local imaging area of ​​a specific scatterer, a parameterized model of the scattering signal in the imaging area is established.

5. The two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement according to claim 4, characterized in that: In step S4, if there is no target scattered echo in the local imaging area of ​​the specific scatterer, the echo data of the specific scatterer is directly reconstructed based on the two-dimensional inverse synthetic aperture ISAR image. The specific process is as follows: The local imaging area of ​​a specific scatterer obtained by the filtered back projection imaging algorithm is subjected to a two-dimensional fast Fourier transform (FFT) to obtain the sector-shaped wavenumber domain data. Then, resampling is performed along the sector-shaped ring to obtain the echo data of the specific scatterer. The resampling formula of the two-dimensional data along the frequency and azimuth angle is: and Where, The vertical index value corresponding to the sampling point on the fan ring or ring, subscript f i is the frequency vector, n y is the number of imaging points in the radial direction of the two-dimensional inverse synthetic aperture ISAR image, L y is the radial imaging distance, θ j is the azimuth corresponding to the sampling point, The subscript a is the horizontal index value corresponding to the sampling point on the fan ring or ring. j Indicates direction, n x is the number of imaging points of the two-dimensional inverse synthetic aperture ISAR image in the lateral direction, L x is the lateral imaging distance.

6. The two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement according to claim 5, characterized in that: In step S4, if there is a target scattered echo in the local imaging area of ​​the specific scatterer, a parameterized model is established for the scattered signal in the imaging area. The specific process is as follows: Based on the complex exponential CE parameterized characterization model, the frequency domain echo signal of a specific scatterer is reconstructed. The specific method is as follows: The CE model expression of the scattering function of a specific scatterer is written as: Where a i , α i and r i are the complex scattering amplitude, frequency dispersion factor and distance to the target reference center of the i-th scattering component, M is the model order, that is, the number of scattering components of the CE model, f is the radar frequency, and c is the electromagnetic wave velocity; Assuming that the kth scattering center characterizing a specific scatterer is represented by the m1th to m2th scattering components of the CE model, the echo signal of this kth scattering center is expressed as: Where m1 and m2 are respectively the main lobe position boundary r of the kth scattering center in HRRP. m1 and r m2 Determined.

7. The two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement according to claim 6, characterized in that: In step S5, the vector subtraction process of the specific scatterer echo data is specifically as follows: For the azimuth-by-azimuth frequency domain scattered echo data, a phasor subtraction process is performed between the target original measurement data and the estimated data of the specific scatterer.

8. The two-dimensional processing method for suppressing specific scatterer echoes in radar cross section measurement according to claim 7, characterized in that: In step S6, the acquired target scattered echo measurement data that varies with frequency and azimuth is used for subsequent target imaging and scattering analysis processing.

Images