Mini SAR Realtime Imaging Processing Technique Based On FPGA

Synthetic aperture radar(SAR)is a high-resolution imaging radar,with the all-time,all-weather operation characteristics,which fills the shortcoming of traditional optical imaging and infrared remote sensing.SAR has the ability of penetrating the mask to obtain the ground region image,which is widely used in battlefield surveillance,natural disaster monitoring and topographic mapping.With the rapid development of small and light aircraft around the world,UAV-based miniature SAR imaging technology has been attracting widespread attention.In this paper,a miniaturized SAR(MiniSAR)imaging system is designed and realized,which is based on the Field Programmable Gate Array(FPGA).The proposed system relies on the efficient Polar Format Algorithm(PFA)to achieve imaging processing,the principle of chirp scaling(PCS)is applied to replace the interpolation to implement the range resampling by complex operation and fast Fourier transforms(FFT).This method can improve the accuracy and efficiency of the algorithm.Then,the high precision interpolation kernel via the SINC function is employed to resample the azimuth signal,obtaining the interpolation results by pipeline,furthermore,enhancing the efficiency of the system.Finally,phase gradient autofocus(PGA)algorithm completes the image focusing processing.This paper is divided into five chapters,and the main content of each part is as follows:Chapter 1 introduces the background of MiniSAR system and its state-of-the-art development,and based on which,we analyze the significance of imaging technology with its application scenarios in the military and civil fields.Compared with the DSP signal processing method,the advantages of the MiniSAR processing system based on FPGA and the key technologies in the FPGA implementation processing are briefly described.Chapter 2 analyzes the characteristics of the MiniSAR dechirped signal,the improved PFA imaging algorithm and PGA focusing technique,which are investigated in detail.And the effectiveness of the imaging algorithm is verified by the point-target simulation results.Chapter 3 starts with the perspective of real-time processing of the MiniSAR echo signal,with the consideration of processing flow and FPGA hardware technology,and then two main modules of data storage and algorithm processing are designed to save hardware resources and improve the computional efficiency in imaging processing.And the specific designing principles of each submodule are drawn in a framework manner.Chapter 4 verifies the robustness of the FPGA signal processing system,and a verification system framework based on host,Ethernet,FPGA and DDR3 SDRAM is integrated.In order to realize the communication between the host and the processing board,a convenient communication module based on Ethernet is designed.Following this,the focusing depth,computional precision,speed of imaging system and resource utilization rate are analyzed.The experimental results show that this FPGA-based real-time imaging processing system of MiniSAR meets the requirements in terms of focusing quality,imaging precision and real-time performance.Finally,the research conclusion remarks are devoted,and the follow-up research is proposed.