Research On Motion Compensation Based On SAR/ISAR Received Signals

Synthetic aperture radar(SAR) is a new type of radar system developed since 1950's. It breaks through the resolution limitation imposed by real aperture. With pulse compression techniques, two-dimensional high resolution imaging to distant targets can be realized. This thesis studies SAR/ISAR motion compensation which based on the received signals.Chapter 1 explains the basic idea of the imaging radar. The history, the latest development and the applications of imaging radar such as SAR/ISAR are also reviewed.Chapter 2 introduces the basic idea and the principle of ISAR at the beginning. Then it studies two kinds of range alignment algorithms of ISAR which are in common use. It also proposes a novel range alignment algorithm based on image cost function and analyzes the relations between forward algorithms and the proposed algorithm. At last it compares the performances of the all algorithms.Chapter 3 discusses three kinds of phase compensation algorithms and compares their performances. Firstly, the principle of Phase Gradient Autofocus and Rank One Phase Estimate and its advanced are detailed. Secondly, it proposes an algorithm of fast maximum contrast phase compensation after discussing its similar algorithm fast minimum entropy phase compensation.Chapter 4 amply analyses the airborne SAR motion compensation mechanism on the range compressed data and proposes its flow chart. The algorithm's robustness is decided by the precision of the Doppler parameter. A Doppler frequency rate estimator based on image cost function is discussed because it has the characteristic of high precision and robustness.Chapter 5 summarizes the whole work of this thesis and points out the problems to be solved in the future.