Research On Airborne SAR Real-time Processing Technology And FMCW-SAR Imaging Theory

SAR is a kind of advanced active microwave remote sensing equipment. It iswidely used as the field surveillance radar system and it is the most used of all the airand space remote sensing systems. Its perfect performance, all-weather and all-timecapacity make SAR become the focus of the world and the developing direction of theradar systems. With the development of the micro-electronics and computertechnology, digital processing technology of SAR data is developing very fast.Nowadays, the real-time processor becomes the essential equipment of SAR system.The dissertation mainly does some research of the SAR real-time processingtechnology. The content of the dissertation includes the principle of the SAR system,real-time imaging algorithm, compensation algorithm of the deviation of the systemand the platform, the SAR real-time processing technology and its implementation.Based on the practice of the project, the dissertation puts emphasizes on some keyproblems of the principle and implementation technology in the SAR real-timeimaging system. The content of the dissertation is the summary of the author's workin his graduate career. The author tried to realize the real-time processing function ofthe system, at the meantime, tried to perfect the function of the processor. Thedissertation also includes some content of FMCW-SAR imaging principle since theauthor did some work of FMCW-SAR during his graduate career.The basic principle of the SAP, system and several SAR imaging algorithm, suchas RD, CS and StepTransform are analyzed first. The different algorithms arecompared in principle and their real-time performance. At the meantime, it isdiscussed in this dissertation about the Cascade FFT algorithm and its application inSAR signal processing. A new Inverse Order Cascade FFT algorithm is providedwhich eliminates the limitation of the traditional algorithm. And some improvementis also provided in this dissertation on the StepTransform algorithm.It is analyzed in this paper about the influence of the nonlinearity of the LFM signal. Then, the sub-aperture processing technology to compensate the nonlinearityof LFM signal is discussed. Combined with the result of the flight experiment, theinfluence of the irregular motion, especially the radial motion of the platform isanalyzed. And it is discussed how to compensate the forward and radial motion of theplatform.This dissertation does some research on how to realize the real-time processingof the SAR signal in the real-time processor based on the practice of the project.Combined with the practical problems, the author makes some research on how torealize the self-adapting technology in the system. The self-adaptive echo locating,self-adaptive filtering and self-adaptive image quantization are analyzed. According tothe motion compensation, the processing scheme in the processor is provided. It isdesigned in the processor on how to image with RD algorithm and it is also discussedon how to image with sub-aperture algorithm in the processor.The principle and the system model of FMCW-SAR are provided in thisdissertation. It is compared with the pulsed SAR system on A/D sampling rate, rangeresolution and swath width. The method to compensate the Doppler Effect and RVP ispresented. Based on the basic pulsed SAR imaging algorithm, we analyze thedifference between the pulsed SAR and FMCW-SAR system and present theimproved algorithm for FMCW-SAR system.