Scattering center modeling method under continuous distance change

Abstract

The invention discloses a scattering center modeling method under continuous distance variation, which comprises the following steps of: performing far-field frequency sweeping, azimuth sweeping and pitching sweeping three-dimensional radar scattering cross section simulation on a target by adopting simulation software to obtain far-field three-dimensional scattering data, and performing near-field to far-field scanning distance radar scattering cross section simulation on the target to obtain continuous distance scattering data; according to the far-field three-dimensional scattering data, scattering images of a target in three dimensional directions are obtained; performing amplitude parameter estimation to obtain a target three-dimensional scattering center model; the distance and the attitude angle from the antenna to each scattering center are obtained, a plurality of scattering fields of each scattering center are reconstructed, and a total scattering field is obtained after vector superposition. According to the method, the amplitude of the scattering center is corrected through the position and angle geometrical relationship between the scattering center and the near-field antenna, scattering data at any distance can be reconstructed through far-field data, and the modeling efficiency is greatly improved while the modeling precision is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of radar target feature modeling, and in particular to a scattering center modeling method under continuous distance variation. Background Art

[0002] In radar target characteristic modeling technology, the scattering center model can describe the electromagnetic scattering characteristics of radar targets. The traditional point scattering center is defined under far-field conditions, without considering the gain transformation of the antenna pattern to the echo. Under continuous distance changes, the distance between the radar transceiver antenna and the target may not meet the far-field conditions. It is necessary to perform near-field correction on the scattering center model in combination with the antenna pattern to complete the RCS (Radar Cross Section) reconstruction at any distance, thereby providing technical support for echo generation and semi-physical simulation under continuous distance.

[0003] In the prior art, in the actual scattering center amplitude correction process, there is a problem that the distance and position of the scattering center cannot be determined, making it impossible to complete the amplitude correction of the radar target. Summary of the invention

[0004] The purpose of the present invention is to provide a scattering center modeling method under continuous distance change, aiming to solve the problem that in the actual scattering center amplitude correction process in the prior art, the distance and position of the scattering center cannot be determined, making it impossible to complete the amplitude correction of the radar target.

[0005] To achieve the above object, the present invention is implemented through the following technical solutions:

[0006] The present invention provides a scattering center modeling method under continuous distance variation, comprising:

[0007] Step S1: using simulation software to perform far-field frequency sweep, azimuth sweep, and elevation sweep three-dimensional radar cross section simulation on the target to obtain far-field three-dimensional scattering data, and performing near-field to far-field sweep range radar cross section simulation on the target to obtain continuous range scattering data, which is used as comparison data for modeling;

[0008] Step S2: interpolating the spherical data in the spherical coordinate system to the rectangular coordinate system according to the far-field three-dimensional scattering data, and then performing an inverse Fourier transform on the interpolated scattering data in each dimension to obtain a scattering imaging of the target in three dimensional directions;

[0009] Step S3: extracting one-dimensional scattering center positions by using the CLEAN algorithm through the scattering imaging in the three-dimensional directions, forming the extracted one-dimensional scattering center positions into candidate positions of three-dimensional scattering centers, and then estimating amplitude parameters of the candidate positions by using the CLEAN algorithm to obtain a target three-dimensional scattering center model;

[0010] Step S4: for the antenna position at continuous distances, the distance and attitude angle from the antenna to each scattering center are obtained in turn, and the distance parameters are corrected. The gain is obtained through the antenna radiation pattern, and the complex scattering field of each scattering center is reconstructed. The total scattering field is obtained after vector superposition, and the total scattering field is compared with the continuous distance scattering data to obtain the similarity between the total scattering field and the continuous distance scattering data.

[0011] Preferably, the far field refers to the distance R between the observation point, i.e., the antenna position, and the center of the simulation target satisfying:

[0012] R>>2D 2 / λ

[0013] Where D is the maximum size of the target, and λ is the wavelength corresponding to the test frequency, that is, the antenna position is in the far field of the target scattering field.

[0014] Preferably, the far-field three-dimensional scattering data refers to a three-dimensional polar coordinate spherical scanning radar scattering cross-section matrix of the target composed of a scanning frequency f±Δf, a scanning azimuth angle φ±Δφ, and a scanning elevation angle θ±Δθ under a given antenna distance R.

[0015] Preferably, the continuous range scattering data refers to a one-dimensional radar cross-section matrix of the target composed of scanning distances at a given test frequency f, azimuth angle φ, and elevation angle θ.

[0016] Preferably, in step S1, simulation software is used to perform far-field frequency sweep, azimuth sweep, and elevation sweep three-dimensional radar cross section simulation on the target to obtain far-field three-dimensional scattering data, which specifically includes:

[0017] Step S1.1: Perform far-field spherical scanning simulation on the target, set the far-field plane wave excitation source, scan frequency f±Δf, scan azimuth angle φ±Δφ, scan pitch angle θ±Δθ, determine the scanning angle and frequency range to be obtained according to the maximum size D of the target, set the number of scanning points according to the resolution requirements, and the imaging lengths in the range and azimuth directions are:

[0018]

[0019] Where c is the speed of light, f, φ, θ are the center frequency, center azimuth, and center elevation angle, 2Δf, 2Δφ, and 2Δθ are the scanning frequency, scanning azimuth, and scanning elevation angle ranges, respectively. W r , W aφ , W aθ They are the imaging lengths in the range, azimuth, and elevation directions, and the corresponding imaging ranges are -W r / 2~W r / 2, -W aφ / 2~Waφ / 2, -W aθ / 2~W aθ / 2, the imaging resolution is:

[0020]

[0021] Where, ΔW r , ΔW aφ , ΔW aθ N is the resolution in range, azimuth and elevation respectively. f 、N a 、N e are the number of scans in the range, azimuth, and elevation directions respectively. The scattering radar cross section value when the operating frequency is f (corresponding to the wave vector k) is expressed as σ(k, φ, θ).

[0022] Preferably, in step S1, a near-field to far-field scanning range radar cross section simulation is performed on the target to obtain continuous range scattering data, which specifically includes: step S1.2: performing a near-field to far-field continuous range scanning simulation on the target, setting the antenna pattern G, frequency f, azimuth angle φ, pitch angle θ, and simulating R 0 Scattering radar cross section at continuous distances to R, recording the number of scan points and scan positions.

[0023] Preferably, the step S2 specifically includes:

[0024] Step S2.1: The coordinates of each polar coordinate point under spherical scanning are non-uniform grid sampling, and the scattering field simulation data under far-field conditions is interpolated to the rectangular coordinate system using nearest interpolation. The 0th order nearest interpolation in the wave vector space is expressed as:

[0025] σ(k x ,k y ,k z )=σ(argmindis(k' x ,k' y ,k' z ))

[0026] Among them, k' x ,k' y ,k z ' represents the wave number in spherical coordinates, k x ,k y ,k z represents the wave number in the rectangular coordinate system, and dis represents the Euclidean distance between the spherical coordinate data position and the rectangular coordinate grid position;

[0027] Step S2.2: Select the interpolated scattered data matrix vector, perform inverse Fourier transform in three dimensions: range, azimuth, and elevation, and obtain three one-dimensional range images of the target in three dimensional directions;

[0028] The three dimensions refer to k in the rectangular coordinate system x ,k y ,k z Three wave vector direction dimensions, the data matrix vector refers to the central data under the three selected dimensions, namely, the sweeping pitch angle data under the central test frequency and central azimuth, the sweeping frequency data under the central pitch angle and central azimuth, and the sweeping azimuth angle data of the central test frequency and central pitch angle. The scattered data is subjected to a one-dimensional inverse Fourier transform to obtain the target range image represented as:

[0029]

[0030] Among them, k i Respectively represent k x ,k y ,k z , Δk i represents the bandwidth of the wave vector, r represents the distance sequence corresponding to the wave vector, r = π / k i , the extracted one-dimensional distance image is recorded as:

[0031] I 0 (r l )=s(r l ),l=1,...,L

[0032] Among them, L is the number of discrete coordinate sequences of the one-dimensional distance image, which is consistent with the number of pairs of sequences in the wave vector in the corresponding dimension.

[0033] Preferably, the step S3 specifically includes:

[0034] Step S3.1: Use the one-dimensional range image scattering center extraction CLEAN algorithm, define the extraction scattering center amplitude cutoff threshold ε, and extract the scattering center position x of the range image, azimuth one-dimensional imaging and elevation one-dimensional imaging respectively. t,sc ,y t,sc ,z t,sc ;

[0035] The one-dimensional CLEAN algorithm is used to extract the scattering centers of the one-dimensional range images in the elevation direction, azimuth direction and range direction respectively. Since the one-dimensional range images in the elevation direction, azimuth direction and range direction are in the same form, the extraction process of the scattering center of the one-dimensional range image in the range direction is also applicable to the extraction of the scattering center of the one-dimensional range image in the azimuth direction and the elevation direction. The process of extracting the scattering center of the target one-dimensional range image using the CLEAN algorithm is as follows:

[0036] Step M1: Initialize the one-dimensional range image, set t = 1:

[0037] I t-1 (x l )=s(x l ),l=1,...,L

[0038] Step M2: Select I t-1 (x l ) is used as the maximum point of the square amplitude as the position estimate of the tth scattering center:

[0039]

[0040] Step M3: Calculate the scattering center position x t,sc The one-dimensional distance image point spread function at is:

[0041]

[0042] estimate The scattering center amplitude at:

[0043]

[0044] I t-1 (x) = [I t-1 (x 1 ),...,I t-1 (x L )] T

[0045] Among them, "T" means transpose and "H" means conjugate transpose;

[0046] |g t,sc | 2 ≥ε, from the distance image I t-1 (x l ) minus the estimated scattering center distance image:

[0047] I t (x l )=I t-1 (x l )-g t,sc h(x l -x t,sc ),l=1,...,L

[0048] t=t+1, go to step M2; when |g t,sc | 2 When <ε, the CLEAN algorithm terminates and the extraction of scattering centers in the one-dimensional range image is completed;

[0049] Step S3.2: Combine the three groups of one-dimensional scattering centers extracted in the range, azimuth, and elevation directions and use them as candidate positions of the scattering centers in three-dimensional imaging. Only the three-dimensional imaging amplitude of the candidate positions of the scattering centers is calculated. The CLEAN algorithm is used to image the target three-dimensional image s(x t ,y t ,z t ) to extract three-dimensional scattering centers;

[0050] The candidate position of the scattering center is recorded as (x t ,y t ,z t ), t=1,...,T,x t ,y t 、z t are the one-dimensional scattering center positions extracted in the range, azimuth, and elevation directions respectively. The imaging result of the scattering center model can be expressed as:

[0051]

[0052] Among them, x i ,y i ,z i is the position of the three-dimensional scattering center to be extracted, and the one-dimensional scattering center position (x t ,y t ,z t ) is equivalent to the coordinates of the corresponding three-dimensional space grid, and h() is the three-dimensional imaging point spread function:

[0053]

[0054] Among them, k x,0 ,k y,0 ,k z,0 represents the starting wave number of frequency domain sampling in range, azimuth and elevation directions, W x ,W y ,W z Respectively represent the imaging width in range, azimuth and elevation, N x ,N y ,N z Respectively represent the number of frequency domain scattering sampling data points in the range, azimuth and elevation directions.

[0055] Preferably, the CLEAN algorithm is used to extract the scattering center of the target in the three-dimensional imaging s(x t ,y t ,z t) is used to extract the three-dimensional scattering center. In each iteration, the position and amplitude of the strongest scattering point in the three-dimensional imaging are found, and the scattering field of the strong scattering point is subtracted from the imaging data until all the strong scattering point features are extracted and the residual data is reduced to below the cutoff threshold.

[0056] Preferably, the step S4 specifically includes:

[0057] Step S4.1: For the CLEAN algorithm, M scattering centers are extracted, and the amplitudes are recorded as a 1 ,...,a M , these M scattering centers are extracted to the observation position v 1 The distances at 1 ,...,r M , r = (x, y, z), the corrected scattering center distance parameter is The angles between the line connecting the scattering center and the antenna position and the observation angle are α 1 ,...,α M , get the gain G corresponding to each angle direction on the antenna pattern 1 ,...,G M , then in v 1 The scattered field at can be expressed as:

[0058]

[0059] Where k is the wave vector, j is a complex number, and v 1 The radar cross section at can be expressed as

[0060] Step S4.2: N observation positions v under continuous distance 1 ,...,v N The scattering field at the position is calculated in turn using the method of step S4.1 to obtain the scattering field at continuous distances. The distance-radar cross section curve reconstructed by the scattering center is compared with the simulation result, and the similarity is represented by the root mean square error:

[0061]

[0062] Where ε is the root mean square error, σ 1 Reconstruct the radar cross section for the scattering center, σ 2 is the simulated radar cross section, and N is the number of sampling points at continuous distances.

[0063] Compared with the prior art, the present invention has the following beneficial effects:

[0064] The scattering center modeling method under continuous distance change provided by the present invention extracts the far-field scattering center through the CLEAN algorithm, and then corrects the scattering center amplitude through the position and angle geometric relationship between the scattering center and the near-field antenna. The scattering data at any distance can be reconstructed through the far-field data, which greatly improves the modeling efficiency while ensuring the modeling accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] In order to more clearly illustrate the technical solution of the present invention, the following briefly introduces the drawings required for the description. Obviously, the drawings described below are an embodiment of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative work:

[0066] Figure 1 A schematic diagram of a flow chart of a scattering center modeling method under continuous distance variation in one embodiment of the present invention;

[0067] Figure 2 A schematic diagram of antenna directions in an embodiment of the present invention;

[0068] Figure 3 This is a comparison diagram of RCS at continuous distances of simulation and reconstruction of a volume target composed of 7 point scattering centers in an embodiment of the present invention. DETAILED DESCRIPTION

[0069] The following is combined with Figure 1-3 The scattering center modeling method under continuous distance change proposed by the present invention is further described in detail with specific implementation methods. According to the following description, the advantages and features of the present invention will be clearer. It should be noted that the drawings are in a very simplified form and use non-precise proportions, which are only used to conveniently and clearly assist in explaining the purpose of the implementation methods of the present invention. In order to make the purposes, features and advantages of the present invention more obvious and easy to understand, please refer to the drawings. It should be noted that the structures, proportions, sizes, etc. illustrated in the drawings of this specification are only used to match the contents disclosed in the specification for people familiar with this technology to understand and read, and are not used to limit the limiting conditions for the implementation of the present invention, so they have no technical substantive significance. Any structural modification, change in proportional relationship or adjustment of size, without affecting the effects that can be produced by the present invention and the purposes that can be achieved, should still fall within the scope of the technical content disclosed by the present invention.

[0070] Near-field parameter correction is an important issue in continuous distance modeling of scattering centers. The present invention adopts one-dimensional and three-dimensional CLEAN algorithms to extract three-dimensional point scattering centers from far-field scattering data. Parameter extraction is to convert the scanning data of the spherical surface into a rectangular coordinate system through nearest interpolation in the case of far-field simulation scattering data in a polar coordinate system, and to correct the scattering centers at different distances using geometric relationships and amplitude corrections. The accuracy of modeling is verified by simulating and reconstructing RCS at continuous distances.

[0071] refer to Figure 1 As shown, the present invention provides a scattering center modeling method under continuous distance variation, comprising:

[0072] Step S1: Use simulation software to perform far-field frequency sweep, azimuth sweep, and elevation sweep three-dimensional radar cross-section simulation on the target to obtain far-field three-dimensional scattering data, and perform near-field to far-field sweep range radar cross-section simulation on the target to obtain continuous range scattering data, which is used as comparison data for modeling.

[0073] The far field refers to the distance R between the observation point, i.e. the antenna position, and the center of the simulation target that satisfies:

[0074] R>>2D 2 / λ

[0075] Where D is the maximum size of the target, and λ is the wavelength corresponding to the test frequency, that is, the antenna position is in the far field of the target scattering field.

[0076] The far-field three-dimensional scattering data refers to the three-dimensional polar coordinate spherical scanning radar cross section matrix of the target composed of the scanning frequency f±Δf, the scanning azimuth angle φ±Δφ, and the scanning elevation angle θ±Δθ under the condition of a given antenna distance R. The continuous distance scattering data refers to the one-dimensional radar cross section matrix of the target composed of the scanning distance under the given test frequency f, azimuth angle φ, and elevation angle θ.

[0077] The simulation software is used to simulate the three-dimensional radar cross section of the target in far-field frequency sweep, azimuth sweep, and pitch sweep to obtain far-field three-dimensional scattering data, including:

[0078] Step S1.1: Perform far-field spherical scanning simulation on the target, set the far-field plane wave excitation source, scan frequency f±Δf, scan azimuth angle φ±Δφ, scan pitch angle θ±Δθ, determine the scanning angle and frequency range to be obtained according to the maximum size D of the target, set the number of scanning points according to the resolution requirements, and the imaging lengths in the range and azimuth directions are:

[0079]

[0080] Where c is the speed of light, f, φ, θ are the center frequency, center azimuth, and center elevation angle, 2Δf, 2Δφ, and 2Δθ are the scanning frequency, scanning azimuth, and scanning elevation angle ranges, respectively. W r , W aφ , W aθ They are the imaging lengths in the range, azimuth, and elevation directions, and the corresponding imaging ranges are -W r / 2~W r / 2, -W aφ / 2~W aφ / 2, -W aθ / 2~W aθ / 2, the imaging resolution is:

[0081]

[0082] Where, ΔW r , ΔW aφ , ΔW aθ N is the resolution in range, azimuth and elevation respectively. f 、N a 、N e are the number of scans in the range, azimuth, and elevation directions respectively. The scattering radar cross section value when the operating frequency is f (corresponding to the wave vector k) is expressed as σ(k, φ, θ).

[0083] Step S1.2: Perform a near-field to far-field scanning range radar cross section simulation on the target to obtain continuous range scattering data. Perform a near-field to far-field continuous range scanning simulation on the target, set the antenna pattern G, frequency f, azimuth angle φ, and pitch angle θ, and simulate R 0 Scattering radar cross section at continuous distances to R, recording the number of scan points and scan positions.

[0084] In this embodiment, metal balls with radii of 0.5 m, 0.2 m, 0.2 m, 0.3 m, 0.3 m, 0.4 m, 0.4 m, and 0.5 m are defined at (-5, 0, 3) m, (-2, 1.5, 2) m, (-2, -1.5, 2) m, (3, 1, 3) m, (3, -6, 3) m, (0, 4, 3) m, (0, -4, 3) m, and (6, 0, 4) m in the near-field electromagnetic software, and the receiving antenna is defined as 100,000 m. The transmitting and receiving antenna patterns are as follows: Figure 2 As shown, the sampling interval is 1 meter, the azimuth angle is 0°, the elevation angle is 90°, the frequency is 10 GHz, the sweep bandwidth is 0.5 GHz, the number of scans is 51, the azimuth and elevation sweep angle widths are both 3°, the number of scans is 61, and the three-dimensional far-field data is obtained by simulation.

[0085] The receiving antenna is defined as a continuous change from 1 meter to 2000 meters, and the transmitting and receiving antenna patterns are as follows Figure 2As shown, the sampling interval is 1 meter, the azimuth angle is 0°, the elevation angle is 90°, and the frequency is 10 GHz. The simulation obtains the next-dimensional near-field data with continuous distance variation in the near-field, which serves as the control group data for scattering center modeling.

[0086] Step S2: According to the far-field three-dimensional scattering data, the spherical data in the spherical coordinate system is interpolated into the rectangular coordinate system, and then the interpolated scattering data is inversely Fourier transformed in each dimension to obtain the scattering imaging of the target in three dimensional directions. Specifically including:

[0087] Step S2.1: The coordinates of each polar coordinate point under spherical scanning are non-uniform grid sampling, and the scattering field simulation data under far-field conditions is interpolated to the rectangular coordinate system using nearest interpolation. The 0th order nearest interpolation in the wave vector space is expressed as:

[0088] σ(k x ,k y ,k z )=σ(argmindis(k' x ,k' y ,k' z )) (3)

[0089] Among them, k' x ,k' y ,k z ' represents the wave number in spherical coordinates, k x ,k y ,k z It represents the wave number in the rectangular coordinate system, and dis represents the Euclidean distance between the spherical coordinate data position and the rectangular coordinate grid position.

[0090] Step S2.2: Select the interpolated scattered data matrix vector, perform inverse Fourier transform in three dimensions: range, azimuth, and elevation, and obtain three one-dimensional range images of the target in three dimensional directions.

[0091] The three dimensions refer to k in the rectangular coordinate system x ,k y ,k z Three wave vector direction dimensions, the data matrix vector refers to the central data under the three selected dimensions, namely, the sweeping pitch angle data under the central test frequency and central azimuth, the sweeping frequency data under the central pitch angle and central azimuth, and the sweeping azimuth angle data of the central test frequency and central pitch angle. The scattered data is subjected to a one-dimensional inverse Fourier transform to obtain the target range image represented as:

[0092]

[0093] Among them, k i Respectively represent k x ,ky ,k z , Δk i represents the bandwidth of the wave vector, r represents the distance sequence corresponding to the wave vector, r = π / k i , the extracted one-dimensional distance image is recorded as:

[0094] I 0 (r l )=s(r l ),l=1,…,L(5)

[0095] Among them, L is the number of discrete coordinate sequences of the one-dimensional distance image, which is consistent with the number of pairs of sequences in the wave vector in the corresponding dimension.

[0096] Step S3: Through the scattering imaging in the three-dimensional directions, the CLEAN algorithm is used to extract the one-dimensional scattering center position, the extracted one-dimensional scattering center position is used to form the candidate position of the three-dimensional scattering center, and then the CLEAN algorithm is used to estimate the amplitude parameters of the candidate position to obtain the target three-dimensional scattering center model. Specifically including:

[0097] Step S3.1: Use the one-dimensional range image scattering center extraction CLEAN algorithm, define the extraction scattering center amplitude cutoff threshold ε, and extract the scattering center position x of the range image, azimuth one-dimensional imaging and elevation one-dimensional imaging respectively. t,sc ,y t,sc ,z t,sc .

[0098] The one-dimensional CLEAN algorithm is used to extract the scattering centers of the one-dimensional range images in the elevation direction, azimuth direction and range direction respectively. Since the one-dimensional range images in the elevation direction, azimuth direction and range direction are in the same form, the extraction process of the scattering center of the one-dimensional range image in the range direction is also applicable to the extraction of the scattering center of the one-dimensional range image in the azimuth direction and the elevation direction. The process of extracting the scattering center of the target one-dimensional range image using the CLEAN algorithm is as follows:

[0099] Step M1: Initialize the one-dimensional range image, set t = 1:

[0100] I t-1 (x l )=s(x l ),l=1,...,L(6)

[0101] Step M2: Select I t-1 (x l ) is used as the maximum point of the square amplitude as the position estimate of the tth scattering center:

[0102]

[0103] Step M3: Calculate the scattering center position x t,scThe one-dimensional distance image point spread function at is:

[0104]

[0105] estimate The scattering center amplitude at:

[0106]

[0107] Where "T" stands for transpose and "H" stands for conjugate transpose.

[0108] |g t,sc | 2 ≥ε, from the distance image I t-1 (x l ) minus the estimated scattering center distance image:

[0109]

[0110] t=t+1, go to step M2; when |g t,sc | 2 When <ε, the CLEAN algorithm terminates and the extraction of scattering centers in the one-dimensional range image is completed.

[0111] Step S3.2: Combine the three groups of one-dimensional scattering centers extracted in the range, azimuth, and elevation directions and use them as candidate positions of the scattering centers in three-dimensional imaging. Only the three-dimensional imaging amplitude of the candidate positions of the scattering centers is calculated. The CLEAN algorithm is used to image the target three-dimensional image s(x t ,y t ,z t ) to extract three-dimensional scattering centers.

[0112] The candidate position of the scattering center is recorded as (x t ,y t ,z t ), t=1,...,T,x t ,y t 、z t are the one-dimensional scattering center positions extracted in the range, azimuth, and elevation directions respectively. The imaging result of the scattering center model can be expressed as:

[0113]

[0114] Among them, x i ,y i ,z i is the position of the three-dimensional scattering center to be extracted, and the one-dimensional scattering center position (x t ,y t ,z t ) is equivalent to the coordinates of the corresponding three-dimensional space grid, and h() is the three-dimensional imaging point spread function:

[0115]

[0116] Among them, k x,0 ,k y,0 ,k z,0 represents the starting wave number of frequency domain sampling in range, azimuth and elevation directions, W x ,W y ,W z Respectively represent the imaging width in range, azimuth and elevation, N x ,N y ,N z Respectively represent the number of frequency domain scattering sampling data points in the range, azimuth and elevation directions.

[0117] The same as the CLEAN algorithm for extracting scattering centers in one-dimensional range images, the CLEAN algorithm is used to extract the target three-dimensional imaging s(x t ,y t ,z t ) is used to extract the three-dimensional scattering center. In each iteration, the position and amplitude of the strongest scattering point in the three-dimensional imaging are found, and the scattering field of the strong scattering point is subtracted from the imaging data until all the strong scattering point features are extracted and the residual data is reduced to below the cutoff threshold.

[0118] Step S4: for the antenna position at continuous distances, the distance and attitude angle from the antenna to each scattering center are obtained in turn, and the distance parameters are corrected, the gain is obtained through the antenna pattern, and the complex scattering field of each scattering center is reconstructed. The total scattering field is obtained after vector superposition, and the total scattering field is compared with the continuous distance scattering data to obtain the similarity between the total scattering field and the continuous distance scattering data. Specifically including:

[0119] Step S4.1: For the CLEAN algorithm, M scattering centers are extracted, and the amplitudes are recorded as a 1 ,...,a M , these M scattering centers are extracted to the observation position v 1 The distances at 1 ,...,r M , r = (x, y, z), the corrected scattering center distance parameter is The angles between the line connecting the scattering center and the antenna position and the observation angle are α 1 ,...,α M , get the gain G corresponding to each angle direction on the antenna pattern 1 ,...,G M , then in v 1 The scattered field at can be expressed as:

[0120]

[0121] Where k is the wave vector, j is a complex number, and v 1 The radar cross section at can be expressed as

[0122] Step S4.2: N observation positions v under continuous distance 1 ,...,v N The scattering field at the position is calculated in turn using the method of step S4.1 to obtain the scattering field at continuous distances. The distance-radar cross section curve reconstructed by the scattering center is compared with the simulation result, and the similarity is represented by the root mean square error:

[0123]

[0124] Where ε is the root mean square error, σ 1 Reconstruct the radar cross section for the scattering center, σ 2 is the simulated radar cross section, and N is the number of sampling points at continuous distances.

[0125] In this embodiment, the RCS obtained by scattering center reconstruction is compared with the simulation result. Figure 3 As shown, the RMS error is 2.41dB.

[0126] In summary, the scattering center modeling method under continuous distance variation provided by this embodiment, compared with the prior art, adopts amplitude correction to model the scattering field, has strong flexibility and expansibility, and quickly generates near-field scattering data under continuous distance through far-field scattering centers, which greatly improves the modeling speed, and the reconstructed RCS is more accurate than direct simulation (such as Figure 3 As shown in the figure, the scattering model established by this method has the ability to quickly model any directional pattern antenna and can provide a fast data generation technology for near-field detection. The far-field scattering center is extracted by the CLEAN algorithm, and the scattering center amplitude is corrected by the position and angle geometric relationship between the scattering center and the near-field antenna. The scattering data at any distance can be reconstructed through the far-field data, which greatly improves the modeling efficiency while ensuring the modeling accuracy.

[0127] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0128] It should be noted that the devices and methods disclosed in the embodiments of this article can also be implemented in other ways. The device implementation described above is only schematic. For example, the flowcharts and block diagrams in the accompanying drawings show the possible architecture, functions and operations of the devices, methods and computer program products according to multiple embodiments of this article. In this regard, each box in the flowchart or block diagram can represent a part of a module, program or code, and the module, program segment or part of the code contains one or more executable instructions for implementing the specified logical function, and the module, program segment or part of the code contains one or more executable instructions for implementing the specified logical function. It should also be noted that in some alternative implementations, the functions marked in the box can also occur in a different order from the order marked in the accompanying drawings. For example, two consecutive boxes can actually be executed substantially in parallel, and they can sometimes be executed in the opposite order, depending on the functions involved. It should also be noted that each box in the block diagram and / or flowchart, and the combination of boxes in the block diagram and / or flowchart can be implemented by a dedicated hardware-based system for performing a specified function or action, or can be implemented by a combination of dedicated hardware and computer instructions.

[0129] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A scattering center modeling method under continuous distance variation, characterized in that: include: Step S1: using simulation software to perform far-field frequency sweep, azimuth sweep, and elevation sweep three-dimensional radar cross section simulation on the target to obtain far-field three-dimensional scattering data, and performing near-field to far-field sweep range radar cross section simulation on the target to obtain continuous range scattering data, which is used as comparison data for modeling; Step S2: interpolating the spherical data in the spherical coordinate system to the rectangular coordinate system according to the far-field three-dimensional scattering data, and then performing an inverse Fourier transform on the interpolated scattering data in each dimension to obtain a scattering imaging of the target in three dimensional directions; Step S3: extracting one-dimensional scattering center positions by using the CLEAN algorithm through the scattering imaging in the three-dimensional directions, forming the extracted one-dimensional scattering center positions into candidate positions of three-dimensional scattering centers, and then estimating amplitude parameters of the candidate positions by using the CLEAN algorithm to obtain a target three-dimensional scattering center model; Step S4: for the antenna position at continuous distances, the distance and attitude angle from the antenna to each scattering center are obtained in turn, and the distance parameters are corrected. The gain is obtained through the antenna radiation pattern, and the complex scattering field of each scattering center is reconstructed. The total scattering field is obtained after vector superposition, and the total scattering field is compared with the continuous distance scattering data to obtain the similarity between the total scattering field and the continuous distance scattering data.

2. The scattering center modeling method under continuous distance variation as claimed in claim 1, characterized in that: The far field refers to the distance R between the observation point, i.e. the antenna position, and the center of the simulation target that satisfies: R>>2D 2 / λ Where D is the maximum size of the target, and λ is the wavelength corresponding to the test frequency, that is, the antenna position is in the far field of the target scattering field.

3. The scattering center modeling method under continuous distance variation as claimed in claim 1, characterized in that: The far-field three-dimensional scattering data refers to the three-dimensional polar coordinate spherical scanning radar scattering cross-section matrix of the target composed of the scanning frequency f±Δf, the scanning azimuth angle θ±Δθ, and the scanning elevation angle θ±Δθ under the condition of a given antenna distance R.

4. The scattering center modeling method under continuous distance variation as claimed in claim 3, characterized in that: The continuous range scattering data refers to a one-dimensional radar cross-section matrix of a target composed of scanning distances at a given test frequency f, azimuth angle φ, and elevation angle θ.

5. The scattering center modeling method under continuous distance variation as claimed in claim 1, characterized in that: In step S1, simulation software is used to perform far-field frequency sweep, azimuth sweep, and elevation sweep three-dimensional radar cross section simulation on the target to obtain far-field three-dimensional scattering data, which specifically includes: Step S1.1: Perform far-field spherical scanning simulation on the target, set the far-field plane wave excitation source, scan frequency f±Δf, scan azimuth angle φ±Δφ, scan pitch angle θ±Δθ, determine the scanning angle and frequency range to be obtained according to the maximum size D of the target, set the number of scanning points according to the resolution requirements, and the imaging lengths in the range and azimuth directions are: Where c is the speed of light, f, φ, θ are the center frequency, center azimuth, and center elevation angle, 2Δf, 2Δφ, and 2Δθ are the scanning frequency, scanning azimuth, and scanning elevation angle ranges, respectively. W r , W aφ , W aθ They are the imaging lengths in the range, azimuth, and elevation directions, and the corresponding imaging ranges are -W r / 2~W r / 2, -W aφ / 2~W aφ / 2, -W aθ / 2~W aθ / 2, the imaging resolution is: Where, ΔW r , ΔW aφ , ΔW aθ are the resolutions in range, azimuth, and elevation, respectively, N f 、N a 、N e are the number of scans in the range, azimuth, and elevation directions respectively. The scattering radar cross section value when the operating frequency is f (corresponding to the wave vector k) is expressed as σ(k, φ, θ).

6. The scattering center modeling method under continuous distance variation as claimed in claim 1, characterized in that: In the step S1, a near-field to far-field scanning range radar cross section simulation is performed on the target to obtain continuous range scattering data, which specifically includes: step S1.2: a near-field to far-field continuous range scanning simulation is performed on the target, the antenna pattern G, frequency f, azimuth angle φ, and pitch angle θ are set, the scattering radar cross section of the continuous distance from R0 to R is simulated, and the number of scanning points and the scanning position are recorded.

7. The scattering center modeling method under continuous distance variation as claimed in claim 1, characterized in that: The step S2 specifically includes: Step S2.1: The coordinates of each polar coordinate point under spherical scanning are non-uniform grid sampling, and the scattering field simulation data under far-field conditions is interpolated to the rectangular coordinate system using nearest interpolation. The 0th order nearest interpolation in the wave vector space is expressed as: σ(k x ,k y ,k z )=σ(argmindis(k' x 'k' y 'k' z )) Among them, k' x ,k' y ,k' z represents the wave number in spherical coordinates, k x ,k y ,k z represents the wave number in the rectangular coordinate system, and dis represents the Euclidean distance between the spherical coordinate data position and the rectangular coordinate grid position; Step S2.2: Select the interpolated scattered data matrix vector, perform inverse Fourier transform in three dimensions: range, azimuth, and elevation, and obtain three one-dimensional range images of the target in three dimensional directions; The three dimensions refer to k in the rectangular coordinate system x ,k y ,k z Three wave vector direction dimensions, the data matrix vector refers to the central data under the three selected dimensions, namely, the sweeping pitch angle data under the central test frequency and central azimuth, the sweeping frequency data under the central pitch angle and central azimuth, and the sweeping azimuth angle data of the central test frequency and central pitch angle. The scattered data is subjected to a one-dimensional inverse Fourier transform to obtain the target range image represented as: Among them, k i Respectively represent k x ,k y ,k z , Δk i represents the bandwidth of the wave vector, r represents the distance sequence corresponding to the wave vector, r = π / k i , the extracted one-dimensional distance image is recorded as: I0(r l )=s(r l ),l=1,...,L Among them, L is the number of discrete coordinate sequences of the one-dimensional distance image, which is consistent with the number of pairs of sequences in the wave vector in the corresponding dimension.

8. The scattering center modeling method under continuous distance variation as claimed in claim 7, characterized in that: The step S3 specifically includes: Step S3.1: Use the one-dimensional range image scattering center extraction CLEAN algorithm, define the extraction scattering center amplitude cutoff threshold ε, and extract the scattering center position x of the range image, azimuth one-dimensional imaging and elevation one-dimensional imaging respectively. t,sc ,y t,sc ,z t,sc ; The one-dimensional CLEAN algorithm is used to extract the scattering centers of the one-dimensional range images in the elevation direction, azimuth direction and range direction respectively. Since the one-dimensional range images in the elevation direction, azimuth direction and range direction are in the same form, the extraction process of the scattering center of the one-dimensional range image in the range direction is also applicable to the extraction of the scattering center of the one-dimensional range image in the azimuth direction and the elevation direction. The process of extracting the scattering center of the target one-dimensional range image using the CLEAN algorithm is as follows: Step M1: Initialize the one-dimensional range image, set t = 1: I t-1 (x l )=s(x l ),l=1,...,L Step M2: Select I t-1 (x l ) is used as the maximum point of the square amplitude as the position estimate of the tth scattering center: Step M3: Calculate the scattering center position x t,sc The one-dimensional distance image point spread function at is: estimate The scattering center amplitude at: I t-1 (x)=[I t-1 (x1),...,I t-1 (x L )] T Among them, "T" means transpose, and "H" means conjugate transpose; |g t,sc | 2 ≥ε, from the distance image I t-1 (x l ) minus the estimated scattering center distance image: I t (x l )=I t-1 (x l )-g t,sc h(x l -x t,sc ),l=1,…,L t=t+1, go to step M2; when |g t,sc | 2 When <ε, the CLEAN algorithm terminates and the extraction of scattering centers in the one-dimensional range image is completed; Step S3.2: Combine the three groups of one-dimensional scattering centers extracted in the range, azimuth, and elevation directions and use them as candidate positions of the scattering centers in three-dimensional imaging. Only the three-dimensional imaging amplitude of the candidate positions of the scattering centers is calculated. The CLEAN algorithm is used to image the target three-dimensional image s(x t ,y t ,z t ) to extract three-dimensional scattering centers; The candidate position of the scattering center is recorded as (x t ,y t ,z t ), t=1,...,T,x t ,y t 、z t are the one-dimensional scattering center positions extracted in the range, azimuth, and elevation directions respectively. The imaging result of the scattering center model can be expressed as: Among them, x i ,y i ,z i is the position of the three-dimensional scattering center to be extracted, and the one-dimensional scattering center position (x t ,y t ,z t ) is equivalent to the coordinates of the corresponding three-dimensional space grid, and h( ) is the three-dimensional imaging point spread function: Among them, k x,0 ,k y,0 ,k z,0 represents the starting wave number of frequency domain sampling in range, azimuth and elevation directions, W x ,W y ,W z Respectively represent the imaging width in range, azimuth and elevation, N x ,N y ,N z Respectively represent the number of frequency domain scattering sampling data points in the range, azimuth and elevation directions.

9. The scattering center modeling method under continuous distance variation as claimed in claim 8, characterized in that: The same as the CLEAN algorithm for extracting scattering centers in one-dimensional range images, the CLEAN algorithm is used to extract the target three-dimensional imaging s(x t ,y t ,z t ) is used to extract the three-dimensional scattering center. In each iteration, the position and amplitude of the strongest scattering point in the three-dimensional imaging are found, and the scattering field of the strong scattering point is subtracted from the imaging data until all the strong scattering point features are extracted and the residual data is reduced to below the cutoff threshold.

10. The scattering center modeling method under continuous distance variation as claimed in claim 9, characterized in that: The step S4 specifically includes: Step S4.1: For the CLEAN algorithm, M scattering centers are extracted, and the amplitudes are recorded as a1,...,a M The distances from the M scattering center extraction positions to the observation position v1 are r1,...,r M , r = (x, y, z), the corrected scattering center distance parameter is The angles between the line connecting the scattering center and the antenna position and the observation angle are α1,...,α M , and obtain the corresponding gain G1,...,G of each angle direction on the antenna pattern M , then the scattered field at v1 can be expressed as: Where k is the wave vector, j is a complex number, and the radar cross section at v1 can be expressed as Step S4.2: Set the N observation positions v1,...,v at the consecutive distances N , the scattering field at each location is calculated using the method in step S4.1 in turn to obtain the scattering field at continuous distances. The distance-radar cross section curve reconstructed from the scattering center is compared with the simulation result, and the similarity is represented by the root mean square error: Where ε is the root mean square error, σ1 is the reconstructed radar cross section of the scattering center, σ2 is the simulated radar cross section, and N is the number of sampling points at continuous distances.

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