Research On SAR Imaging Method Of Radar Ground Target Based On FPGA

Synthetic Aperture Radar(SAR),as an all-weather,long-distance active detection imaging radar,breaks through the limitation of the resolution of the real-aperture antenna in the direction of the direction when imaging,and achieves high resolution of detection targets Rate imaging,widely used in ground target imaging scenes.Aiming at the problem that the fast and efficient processing of a large number of echo data during SAR imaging is difficult to achieve in a traditional digital signal processor,this paper uses the Field P rogrammable Gate Array(FPGA)modular,high-speed parallel data processing characteristics,Studied the SAR imaging method of radar ground target based on FPGA,The following is the research content and results.First part,this paper studies the basic theory of SAR imaging,builds an airborne SAR imaging simulation platform and establishes a time-domain echo model to generate SAR echo data for subsequent research.The research compares the principle and imaging effect of conventional range Doppler(Range Doppler,RD)algorithm,improved RD algorithm and Chirp Scaling(CS)algorithm.Combining with the premise of SAR imaging processing based on FPGA hardware platform in this paper,according to the calculation amount and imaging accuracy of the algorithm,the improved RD algorithm with low hardware resource consumption,high imaging accuracy and fast processing speed is selected as the subsequent SAR imaging signal processing algorithm.In addition,the algorithm uses Fast Fourier Transformation(FFT)to obtain the frequency of the narrowband echo signal with low accuracy.It is proposed to use Chirp-Z Transform(CZT)to fine-tune the frequency of the echo signal.Therefore,the frequency accuracy of the narrowband echo signal is improved.Second part,an FPGA-based SAR imaging processing scheme is designed,which mainly includes the preprocessing of SAR echo signals and SAR imaging algorithms.The preprocessing mainly completes the frequency reduction processing of the SAR intermediate frequency echo signal,and reduces the amount of data in the subsequent imaging algorithm processing.The SAR imaging algorithm part mainly completes range pulse compression,range migration correction and azimuth pulse compression.Third part,the designed SAR imaging scheme is realized based on FPGA.Use the VIVADO SIMULATOR tool in the VIVADO software to perform functional simulation on each module of the design scheme,and compare with the theoretical simulation results.The results show that the maximum relative error between the SAR imaging results processed by FPGA and the theoretical simulation results of MATLAB does not exceed 0.14%,which meets the expected index requirements.In addition,the CZT time-frequency conversion module is implemented based on FPGA,and the pulse compression of the range echo signal is completed by using CZT.The result obtained is 2.52 m higher than the accuracy of the range pulse result obtained by the FFT method.This shows that the SAR imaging processing scheme and related improvement methods designed in this paper can be correctly implemented in FPGA hardware and meet the accuracy requirements of SAR imaging processing.