Corner reflector array design method based on scatter center extraction

Abstract

The application discloses a corner reflector array design method based on scattering center extraction, which studies and analyzes electromagnetic scattering characteristics of metal targets in a complex scene, and provides a feasible scheme for electromagnetic concealment of important targets, and specific contents comprise the following steps: a property scattering center model of a target is extracted according to a radar echo, and coordinate parameters of the model are used for initial arrangement of the corner reflector array; a structural similarity is used as a target function to optimize the corner reflector array, and is used as a quality evaluation index of arrangement of the corner reflector array; and finally, a false target similar to scattering characteristics of the target is obtained by constructing the corner reflector array. According to the method, the arrangement of the corner reflector array in the complex scene has a hiding performance of more than 90% to the target, and has high similarity compared with a radar image of the target.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of radar echo detection, and particularly relates to a corner reflector array design method based on scattering center extraction. BACKGROUND

[0002] As a mature and reliable passive jamming device, the corner reflector can generate a very strong echo signal in the radar irradiation direction due to its special structure, and can simulate a target radar scattering characteristic much larger than the size of the corner reflector itself. The corner reflector can play a jamming and deception role against the terminal guidance radar of an anti-ship missile. For a radar with high-resolution distance imaging capability, a single corner reflector is difficult to meet the requirements of the jamming function due to the limitation of its size and the incident angle. A ship is often detected as an extended target, so the ship is usually laid out in the form of an array composed of multiple corner reflectors, which can simulate a target and play an important protection role for the target.

[0003] The scattering center coordinates and attitude angles extracted by the attribute scattering center extraction method are used as the initial solution of the corner reflector array arrangement, the array optimization algorithm is used to calculate the radar image structural similarity of the corner reflector array and the target, the problem of difficult generation of the radar image is overcome, and the corresponding corner reflector array can be designed for different targets. The ship corner reflector decoy is born in the actual combat demand, and the construction research of the corner reflector array has high practical value and application prospect. SUMMARY

[0004] The purpose of the application is to provide a corner reflector array design method based on scattering center extraction, which uses the fast imaging simulation technology based on the bounce ray method to analyze the scattering characteristics of different types of corner reflectors.

[0005] The technical solution for achieving the purpose of the application is as follows: in a first aspect, the application provides a corner reflector array design method based on scattering center extraction, and the steps are as follows:

[0006] Step 1: based on the parameters of the radar echo and the incident wave, the attribute scattering center parameters of the target are extracted, and the initial arrangement of the corner reflector array is performed.

[0007] Step 2: based on the initial arrangement of the corner reflector array, an iterative optimization corner reflector array model is constructed, the structural similarity of the radar simulation image is used as the optimization target, and the actual limitation of the corner reflector arrangement is used as the nonlinear constraint condition.

[0008] In a second aspect, the application provides a computer device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the method of the first aspect when executing the program.

[0009] In a third aspect, the present application provides a computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the steps of the method of the first aspect.

[0010] In a fourth aspect, the present application provides a computer program product comprising a computer program which, when executed by a processor, implements the steps of the method of the first aspect.

[0011] Compared with the prior art, the present application has the following advantages: (1) the initial arrangement of the corner reflector array can be quickly generated through the attribute scattering center extraction, and the accuracy of the corner reflector array design arrangement is improved; (2) the non-uniform array arrangement method can better fit the target scattering characteristics, and the target protection performance is better under high-resolution SAR. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 It is a flow chart of a corner reflector array design method based on scattering center extraction. DETAILED DESCRIPTION

[0013] The present application discloses a corner reflector array design method based on scattering center extraction. The method analyzes the electromagnetic scattering characteristics of metal targets in complex scenes, providing a feasible scheme for electromagnetic concealment of important targets. A corner reflector array with high similarity to the target radar image is generated, improving the electromagnetic concealment performance of the corner reflector array arrangement.

[0014] The method uses a fast imaging simulation technology based on the bounce ray method to analyze the scattering characteristics of different types of corner reflectors. On this basis, a corner reflector array construction method based on attribute scattering center parameter extraction is proposed. The coordinate parameters extracted from the attribute scattering center model are used for the initial arrangement of the corner reflector array. The structural similarity is used as the objective function to optimize the corner reflector array, and finally the corner reflector array construction false target is obtained. The simulation results show that the method has a target concealment performance of more than 90% for the corner reflector array arrangement in complex scenes, and has high similarity to the target radar image. Combined with the Figure 1 The specific steps of the method are as follows:

[0015] Step 1, corner reflector array initial arrangement step: based on the parameters of the radar echo and the incident wave, the attribute scattering center parameters of the target are extracted, and the corner reflector array is initially designed;

[0016] Step 2, corner reflector array optimization step: based on the initial arrangement of the corner reflector array, an iterative optimization corner reflector array model is constructed, the structural similarity of the radar simulation image is used as the optimization target, and the actual restriction of the corner reflector arrangement is used as the nonlinear constraint condition.

[0017] The attributed scattering center (ASC) is designed according to the attribute scattering center parameter model (ASC) in step 1. The scattering center is a basic feature of a high-resolution SAR image. The ASC parameter is extracted based on the radar echo of the SAR image. In the SBR method, the two-dimensional fast imaging formula at an arbitrary observation point with a distance of r, an elevation angle of θ, and an azimuth angle of φ is as follows:

[0018]

[0019] wherein ζ i is a scattering electric field frequency correlation factor, R and C R represent the coordinates in the range direction and the azimuth direction respectively, Δk is a radar scanning beam interval, k0 is a radar, θ0 is an angle formed by the incident direction and the aperture plane, irays is the i-th ray tube, (ΔA) exit is an integral area of the ray tube and the target surface, is a position vector at the center point A of (ΔA) exit ; is an observation point wave vector, is a unit vector perpendicular to . sinc(u) = sin(u) / u, d i is the path length of the i-th ray between the incident point and the exit point. represents the position coordinates of any one vertex of the triangular facet, which represents the propagation distance of the ray in the process of contacting the target twice.

[0020] Based on the above radar image signal, the two-dimensional inverse Fourier transform of the signal is performed, and the transformed signal is shifted so that the small frequency is at the center. Then the scattering center is extracted from the target echo signal. The parameter information of the ASC can represent the dependence between the electromagnetic scattering characteristics and the signal frequency and angle. The ASC is divided into distributed scattering centers and local scattering centers. The specific expression of the ASC is as follows:

[0021]

[0022] wherein Num represents the total number of scattering centers, E i represents the scattering field of the i-th scattering center. A i represents the scattering amplitude coefficient of the i-th scattering center, f represents the radar signal frequency, f c then represents the signal center frequency. L i represents the length of the scattering center, then represents the azimuth angle between the radar and the target,​​​ denotes the tilt angle of the ith scatterer, x i and y i denote the distance coordinates of the ith scatterer with respect to the reference point. a i denotes the frequency-dependent factor. g i represents the angle-dependent factor of the scatterer. When L i > 0, the ith scatterer is a distributed scatterer; when L i = 0, the ith scatterer is a local scatterer, in which case a e {-1, 0, 1}. Due to the excessive number of parameters of the ASC model, this paper adopts the method of dictionary scaling and alternating optimization to reduce the computational complexity of the dictionary matrix. By combining the parameter grid dimension reduction method based on the full dictionary and the RELAX algorithm, the computational complexity is effectively reduced, and the performance of the algorithm under high resolution and the accuracy of the final parameter estimation are guaranteed. Finally, the number of target scatterers and the parameters of each scatterer are obtained.

[0023] The corner reflector array iterative optimization method described in step 2; the coordinates of the corner reflector array are iteratively optimized using a bionics optimization algorithm. The structural similarity of the corner reflector array and the radar image of the target is calculated as the fitness function. Compared with the current mainstream bionics optimization algorithm, the convergence effect and iterative calculation process gradient descent of the grey wolf optimization algorithm are better, so this section uses the grey wolf optimization algorithm to calculate the structural similarity of the corner reflector array and the radar image of the target as the fitness function, and the optimization parameters are The array has K corner reflectors, x k , y k , z k are the coordinates of the kth corner reflector on the Cartesian coordinate axes. g k , g k are the angles between the kth corner reflector and the x, y, z axes. Before the optimization starts, the extracted scatterer parameters are used as initial values, and are set to 0, which are substituted into the corner reflector array optimization algorithm. In the grey wolf optimization algorithm, the top three wolves with the highest fitness scores are designated as a, b, and d, which lead other wolves w to search for the target position and update the position around a, b, and d:

[0024]

[0025] where, and represent the distances between a, b, d and other individuals, respectively; and represent the current positions of a, b, and d, respectively; is a random vector, It represents the current iteration step optimization position.

[0026] Generally, optimization problems can be described from three aspects: optimization variables, constraint functions, and objective functions. For the optimization problem of a corner reflector array, the optimization objective is to maximize the structural similarity (SSIM) of the image. Structural similarity, from the perspective of image composition, defines structural information as a combination of three different factors representing distortion: brightness, contrast, and structure. The expression for SSIM is:

[0027]

[0028] Let μ p and μ q These are the average pixel intensities of images p and q, respectively, and σ is the average pixel intensity. p and σ q These are the standard deviations of images p and q, respectively, and σ is the standard deviation of p and q. pq C is the covariance of p and q. k1 =(k1*Li) 2 C k2 =(k2*Li) 2 , where Li represents the maximum value of the pixel values ​​in the image, typically 255. k1 and k2 are set to avoid a denominator of 0. The SSIM value ranges from 0 to 1; the larger the SSIM, the higher the similarity between the two images. SSIM reaches its maximum exponential value of 1 if and only if the images are identical.

[0029] Finally, considering practical location requirements, the minimum distance between two corner reflectors is defined as 0.5 meters. Meanwhile, to ensure that the coordinates of each corner reflector lie within the location range required by the bouncing ray method, the entire optimization process of the array must adhere to the following constraints:

[0030]

[0031] Among them, R min =(x min ,y min ,z min ),R max =(x max ,y max ,z max ) represents the upper and lower limits of the coordinates for iterative optimization.

[0032] The above merely is the preferred embodiment of the present application, it should be pointed out that, for the ordinary skilled in the technical field, without departing from the principles of the present application, can also make a number of improvements and refinements, these improvements and refinements should also be considered as the protection scope of the present application. The components not explicitly in the embodiments can be implemented by the prior art.

Claims

1. A corner reflector array design method based on scatterer extraction, characterized by, The steps are as follows: Step 1: based on the radar echo and the parameters of the incident wave, the attribute scattering center parameters of the target are extracted, and the initial arrangement of the corner reflector array is carried out; Step 2: based on the initial arrangement of the corner reflector array, an iterative optimization corner reflector array model is constructed, the structural similarity of the radar simulation image is taken as the optimization target, and the actual limitation of the corner reflector arrangement is taken as the nonlinear constraint condition; The grey wolf optimization algorithm is used to iteratively optimize the coordinates of the corner reflector array; The structural similarity of the radar image of the corner reflector array and the target is calculated as a fitness function, and the optimization parameters are The array has K corner reflectors, x k ,y k ,z k is the coordinate of the kth corner reflector on the Cartesian coordinate axis; The extracted scattering center parameters are taken as initial values before the optimization begins, and at the same time, the initial values of (z0, θ0, φ0) are set to 0, which are substituted into the corner reflector array optimization algorithm; in the grey wolf optimization algorithm, the top three wolves with the highest fitness scores are designated as α, β and δ, which lead other wolves ω to search for the target position and update the position around α, β and δ: where, and denote the distances between a, b, d and other individuals, respectively; and denote the current positions of a, b and d, respectively; is a random vector, is the position optimized at the current iteration step. The minimum distance between two corner reflectors is defined as 0.5 meters; in order to ensure that the coordinates of each corner reflector are located in the position interval meeting the requirements of the bounce ray method, the entire optimization process of the array complies with the following constraint conditions: where R min = (x min , y min , z min ), R max = (x max , y max , z max ) are lower and upper bounds of the coordinates of the iterative optimization.

2. The corner reflector array design method based on scatterer extraction according to claim 1, wherein, In step 1, the radar is SAR, in order to obtain the echo information of the SAR image, first, the image is subjected to two-dimensional inverse Fourier transform, and the transformed signal is shifted so that the small frequency is at the center; then the attribute scattering center is extracted from the target echo signal; the parameter information of the attribute scattering center represents the dependence relationship between the electromagnetic scattering characteristics and the signal frequency and angle; the attribute scattering center is divided into distributed scattering center and local scattering center; the specific expression of the attribute scattering center is as follows: where Num represents the total number of scattering centers, E i represents the scattering field of the ith scattering center; A i represents the scattering amplitude coefficient of the ith scattering center, f represents the frequency of the radar signal, f c represents the signal center frequency; L i represents the length of the scattering center, represents the azimuth angle between the radar and the target, represents the tilt angle of the ith scattering center, x i and y i respectively represent the distance coordinates of the scattering center i relative to the reference point; α i represents the frequency-dependent factor; γ i represents the angle-dependent factor of the scattering center; when L i > 0, the scattering center i is a distributed scattering center; when L i = 0, the scattering center i is a local scattering center, and at this time α ∈ {-1, 0, 1}.

3. A computer device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the program to realize the steps of the method in any one of claims 1-2.

4. A computer-readable storage medium having stored thereon a computer program, characterized in that, The program is executed by the processor to realize the steps of the method in any one of claims 1-2.

5. A computer program product comprising a computer program, characterized in that, The computer program is executed by the processor to realize the steps of the method in any one of claims 1-2. The computer program is executed by the processor to realize the steps of the method in any one of claims 1-2.

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