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CN-121978688-A - SAR imaging rapid simulation method, device and equipment based on electromagnetic calculation

CN121978688ACN 121978688 ACN121978688 ACN 121978688ACN-121978688-A

Abstract

The invention relates to the technical field of radar imaging simulation, in particular to a SAR imaging rapid simulation method, device and equipment based on electromagnetic calculation; the method comprises the steps of firstly determining a scene of SAR imaging, comprising signal parameters, radar position information and target information, secondly constructing an LFM signal, carrying out rapid frequency domain simulation according to an electromagnetic calculation method based on Z-buffer shielding judgment to obtain RCS data, then convolving the LFM signal and the RCS data to obtain radar echo signals, sequentially carrying out down-conversion, distance pulse compression, azimuth pulse compression and other operations on the echo signals to obtain a two-dimensional SAR image, and rapidly simulating echo signals of the target and carrying out SAR imaging by utilizing an electromagnetic calculation mode combining a physical optical method based on Z-buffer shielding judgment with parallel calculation and difference frequency sweep, wherein simulation results are more accurate than traditional methods based on ideal scattering points and faster than traditional electromagnetic algorithm speeds.

Inventors

  • YUAN HAOBO
  • WANG ZHIRUO
  • HOU YUCHEN

Assignees

  • 西安电子科技大学

Dates

Publication Date
20260505
Application Date
20260130

Claims (10)

  1. 1. The SAR imaging rapid simulation method based on electromagnetic calculation is characterized by comprising the following steps of: S1, determining scene information of SAR imaging and establishing a target geometric model, wherein the scene information comprises signal parameters, radar position information and target information; s2, performing frequency domain electromagnetic simulation on the target geometric model in the step S1 by adopting a physical optical method to obtain frequency domain data H (j omega) of RCS of the target geometric model; S3, transforming the frequency domain data H (j omega) of the RCS in the step S2 to the time domain to obtain the time domain data of the RCS (T) calculating a chirp signal using the signal parameters described in step S1 And time domain data of the RCS (T) convolving to obtain echo signals ; S4, for the echo signal in the step S3 Sequentially performing down-conversion, distance pulse compression and azimuth pulse compression to obtain a two-dimensional SAR image; The physical optical method in step S2 specifically includes the following steps: s2.1 reconstructing the surface of the target geometric model of step S1 with M (m=1, 2,..m) triangle units; S2.2, carrying out shielding judgment on M (M=1, 2,.. Fwdarw., M) triangle units in the step S2.1 through a depth buffer Z-buffer algorithm to obtain a bright area triangle set; s2.3, selecting RWG basis function to calculate the induction current generated on the surface of the triangle collection of the bright area in the step S2.2, and integrating the induction current and the divergence thereof through a green function of free space to obtain a scattered field Further calculate the frequency domain data of RCS In which a current is induced Scattered field And frequency domain data of RCS The calculation formula of (2) is as follows: In the formula, In order to induce a current flow, In order to scatter the field of view, As a normal vector to the direction of the beam, For the incident magnetic field to be incident, In order to be of an angular frequency, In order to be of magnetic permeability, For the dielectric constant of the material to be a dielectric constant, Representing a field point to source point vector, As the distance from the field point to the source point, Is a green's function.
  2. 2. The SAR imaging rapid simulation method according to claim 1, wherein the occlusion judgment in step S2.2 specifically comprises the following sub-steps: s2.2.1 dividing the background plane in the scene information described in step S1 into Multiple grids, each for Representation, 1 therein ≤ 、1≤ ≤ Then, the M (m=1, 2,..once., M) triangle units described in step S1 are projected onto a background plane from the light source position, respectively, to define an array Representing blocking different grids Triangle unit numbering of (2); s2.2.2 for the 1 st triangle element of the projection of step S2.2.1, if a grid on the background plane Is occluded by the 1 st triangle unit, then the grid is given Corresponding array Assigning 1 and recording the number of projected grids of the 1 st triangle unit on the background plane For the projected M (m=2, 3,..m) th triangle element of step S2.2.1, for the occluded and unassigned mesh Directly to the grid Corresponding array Assignment M, where m=2, 3,..m, M, for a grid that is occluded but has been assigned The M (m=2, 3..m) th triangle unit is compared with the M (m=2, 3..m) ( < M) distances from the triangle units to the light source positions, respectively, array Is to take the triangle unit number nearer to the light source and then record the number of projected grids of the triangle unit on the background plane And repeating the process, wherein the process is repeated, until all M (m=2, 3, M) the triangle units complete projection operation; S2.2.3 calculate the array of different assignments described in step S2.2.2 Corresponding grid Number of (3) Wherein M=1, 2 3.. The term M, if it is The triangle unit is a bright area triangle, and all the bright area triangles form a bright area triangle set.
  3. 3. The SAR imaging rapid simulation method of claim 1, wherein the operations of step S2.2 and step S2.3 are completed by MPI parallel computation.
  4. 4. The SAR imaging fast simulation method of claim 1, wherein the frequency domain data of the RCS of step S2.3 is approximated using a rational interpolation polynomial And then analyzing the zero poles of the rational interpolation polynomial, and correcting the causality of the rational interpolation polynomial by an analysis method.
  5. 5. The SAR imaging fast simulation method of claim 1, wherein the chirp signal of step S3 The expression of (2) is as follows: Wherein, the , As a result of the center frequency, Is a variable of the total time of day, In the form of a pulse width, For frequency adjustment; The echo signal The expression of (2) is as follows: 。
  6. 6. the SAR imaging fast simulation method of claim 1, wherein in the down-conversion of step S4, the selected reference signal The expression of (2) is as follows: After the echo signal is demodulated The expression of (2) is as follows: Wherein, the In order to receive the signal(s), For the attenuation of the signal after spatial transmission, For the distance of the target to the emission point, Is the speed of light.
  7. 7. The SAR imaging fast simulation method according to claim 1, wherein in the distance pulse compression of step S4, the down-converted echo signal is processed by a matched filtering technique Processing, specifically, adopting convolution operation to complete matched filtering, and making long-time signal pulse Compressed into a short time pulse ; When the radar flies from A to B in a uniform linear mode, a period T is taken as a pulse interval, a linear frequency modulation signal is transmitted, and a received echo signal can be expressed as a mathematical form containing target information after demodulation processing: Wherein, the Is the azimuth time variable, and the time variable, Is a distance-to-time variable that, Is the distance from each sampling point to the target point; System function of selected matched filter Expressed as: Wherein, the Taking the minimum distance between all sampling points and an observation range by referring to the inclined distance; Expressed as: 。
  8. 8. The SAR imaging rapid simulation method of claim 1, wherein the azimuth pulse compression of step S4 sequentially comprises three sub-steps of scene meshing, migration curve determination, and signal coherence accumulation, wherein any mesh point in the scene meshing Corresponding echo signal Expressed as: wherein Mslow is the number of pulses, i.e. the number of samples over the aperture, For grid points Distance to the nth sampling point.
  9. 9. An apparatus for implementing the SAR imaging rapid simulation method of any one of claims 1 to 8, comprising: the target geometric modeling module is used for determining scene information of SAR imaging and establishing a target geometric model, wherein the scene information comprises signal parameters, radar position information and target information; The frequency domain electromagnetic simulation module is used for carrying out frequency domain electromagnetic simulation on the target geometric model by adopting a physical optical method to obtain frequency domain data H (j omega) of RCS of the target geometric model; the module for generating echo signals converts the frequency domain data H (j omega) of the RCS into the time domain to obtain the time domain data of the RCS (T) calculating a chirp signal using said signal parameter And time domain data of the RCS (T) convolving to obtain an echo signal; and the SAR imaging module is used for sequentially carrying out down-conversion, distance pulse compression and azimuth pulse compression on the echo signals to obtain a two-dimensional SAR image.
  10. 10. An electronic device comprising a memory and a processor, wherein: a memory for storing a computer program for implementing the SAR imaging rapid simulation method of any one of claims 1 to 8; a processor for implementing the SAR imaging fast simulation method according to any one of claims 1 to 8 when executing the computer program.

Description

SAR imaging rapid simulation method, device and equipment based on electromagnetic calculation Technical Field The invention relates to the technical field of radar imaging, in particular to a SAR imaging rapid simulation method, device and equipment based on electromagnetic calculation. Background The electromagnetic waves emitted by the radar system will scatter after reaching the target. The scattering characteristics of electromagnetic waves depend on the environment in which the target is located, as well as factors such as the shape, size, material and the like, and the scattered waves can return to a radar receiver in different modes, and the return signals are radar echoes. Synthetic aperture radar SAR imaging is a technology for performing high-resolution imaging on a target by utilizing a plurality of echo signals on the basis of electromagnetic scattering and radar echo, and is widely applied to the fields of military reconnaissance, environmental monitoring, geological exploration, disaster assessment and the like. Unlike conventional radars, SAR achieves higher resolution than the actual physical size of the antenna by synthesizing multiple echo data to form a "synthetic aperture". The development process of the electromagnetic computing method can be roughly divided into three key stages of an analysis method, an approximation method and a numerical method. The result of the analytical method is mathematically very strict with little error, but when the shape of the structure is complex, the analytical method will fail, which limits the application range of the analytical method to a large extent. The solution can be performed by approximation methods at this time. Approximation methods tend to approximate maxwell's equations according to certain specific conditions, obtaining some form of compact solution by sacrificing accuracy. The approximation method is mainly a kind of optical method such as physical optical method, geometrical optical method, consistent geometrical diffraction method, and the like. With the development of computer computing power, full-wave simulation algorithms based on numerical computation have evolved from explosion, with the most classical being finite element methods, time domain finite difference algorithms, moment methods, and fast multipole techniques. In the development process of SAR imaging algorithm in a large and medium-sized target wide frequency band, a large amount of echo data is required to be tested and verified. The performance of radar systems is usually estimated and optimized by constructing and simulating echo signals of ideal scattering points, but the signals are not realistic and the SAR images are inaccurate. The more accurate approach is to model the target in three dimensions, then simulate the echo by adopting an electromagnetic calculation method, and finally perform SAR imaging simulation. Common electromagnetic calculation methods, such as a moment method, have high accuracy but high calculation complexity and low calculation efficiency, a rapid multi-machine method has high accuracy, less memory and high speed but needs to consider the problem of iteration convergence, a regional decomposition method has high speed but uses a field Jing Shouxian, and a bouncing ray method has high calculation accuracy and is suitable for various situations but has complex calculation process and high calculation resource consumption. There is therefore also a need to improve the speed and accuracy of radar cross-sectional area RCS simulation by new techniques. The GPU ray tracing method is developed based on the bouncing ray method and has the advantages of high calculation accuracy and high GPU calculation speed, but CUDA core libraries called in codes cannot be modified. The Polish develops a method between a physical optical method and an ideal scattering point, and simulates an echo signal by dispersing a surface into the ideal point, approximating calculation of a reflection coefficient and simple shielding judgment. The radial tracking engine POV-Ray is developed in 2016 in Germany, is the only free SAR imaging simulation software based on electromagnetic simulation at present, and has high speed. In the prior art, the patent publication number is CN 109188384A, the name is the electromagnetic simulation method of the dynamic observation of the echo of the space target, the electromagnetic simulation method of the dynamic observation of the echo of the space target is disclosed, the dynamic observation view angle and the optimal observation time of the space target are calculated through the positions of the space target and a ground observation station, the electromagnetic scattering of the space target is calculated by using a large-bin physical optical method at the dynamic observation view angle of the optimal observation time, the echo of the space target is obtained and imaged, the effective electromagnetic simulation and imaging of the sp