A SAR Echo Simulation Method Of FDTD Calculation Based On Moving Excitaion Source

SAR has played an important role in the field of remote sensing since its birth.With the continuous improvement of detection level and data acquisition capability,the simulation requirements for SAR systems are becoming more and more intense.Echo simulation plays a huge role in SAR system simulation,and there are usually time method and frequency domain method The time domain numerical method is widely used in target electromagnetic simulation because it is superior to the frequency domain method in the high precision of complex target simulation.For the electromagnetic large size target,this paper uses the FDTD method to simulate the target electromagnetic characteristics,and uses the FDTD algorithm to obtain the far-field receiving signal,and then obtain the SAR original echo data.The SAR image is obtained by the imaging algorithm to verify the correctness of the electromagnetic simulation and echo simulation process.Based on the traditional time domain simulation FDTD method,the introduction of the excitation source is improved.Considering the motion of the platform in SAR simulation,the FDTD method based on moving excitation source is proposed to improve the accuracy of the FDTD simulation signal and make the target electromagnetic simulation and the actual detection process more highly integrated.The theory of moving excitation source mainly consists of two parts: the radiation stage of electromagnetic wave.According to the moving equation of the radar platform,the excitation signal is not equally spaced,and the instantaneous value of the electric field and the magnetic field at the time of the electromagnetic wave iteration time step is derived,and the moving excitation signal is introduced into the Total-Field-Scattering-Field boundary;the stage od radar platform receives the scattering echo,and needs to calculate the far field distance value in the FDTD simulation according to the electromagnetic wave transmission process.A complete moving excitation signal is introduced from both the transmission and receiving processes.For the simulation of the original echo of the target,according to the distance information of the visible cell,the radar received signal is superimpo sed according to the time delay.And on the condition that the change of the electromagnetic property of the visible cell is negligible within the length of t he synthetic aperture,we can obtain the receiving signal data at all the azimuth sampling position.Use the orthogonal demodulation to obtain the SAR original echo signal and compare and analyze the performance of different targets in the simulation characteristics.The experimental simulation carried out electromagnetic simulation and echo generation for the simulated point target and the electromagnetic large size target,and verified the correctness of the simulation results of the large-scale simulation target echo using the the highly versatile R-D algorithm.By analyzing and comparing the simulation results,the correctness of the electromagnetic simulation and SAR echo simulation method is proved by the imaging simulation results of the point target and the electromagnetic large size target under the specific resolution limit and specific imaging area.Finally,through the intuitive SAR imaging results,the accuracy of the simulation results under the moving excitation FDTD and the traditional FDTD simulation is compared and analyzed.It is proved that the mobile excitation source is superior to the non-mobile excitation source in echo simulation and imaging simulation,.This method has practical meaning and value in obtaining the electromagnetic characteristics of the electromagnetic large size target.