High-resolution Airborne Sar Signal Processing Research

Yuehua Liu (Major: Communications and Information System)Directed by Professor Linjiao iingSynthetic aperture radar (SAR) has been a new means for the observation of the earth's surface since 1950's. Currently, to obtain high resolution airborne SAR image is one of the most important directions of SAR. The research work of this thesis mainly focuses on two aspects, one is imaging algorithm, the other is autofocus algorithms. Use them to process real data, We get right results.The introduction firstly explains the essentials of SAR in a variety of aspects. and also discusses its characteristics and application.Chapter 2 treats the basic principle of SAR from views of pulse compression and synthetic array. Chapter 3 details the realization of imaging algorithm, for the real data recorded by Institute of Electronics, Chinese Academy of Sci ences(IECAS). I calculate its range resolution and azimuth resolution. After being dealt by imaging algorithm, radar images are obtained.In ideal circumstances, the back scattered echo signal of SAR is chirp signal. With synthetic aperture theory, high azimuth resolution imaging to distant targets can be attained. However, in fact, undesirable phase errors exist. This paper analyzes the effect phase errors on the radar image in detail, such phase errors in a SAR si~na1 history degrade image quality in several ways, such as geometric distortion, loss of resolution, decrease in image contrast, spurious targets, and a reduction in signal-tonoise ratio.To obtain high resolution SAR image, the key technique is motion compensation, which includes autofocus algorithm. Autofocus algorithm improve image quality by removing a large part of all kinds of phase errors in SAR echo signal. In this paper, I describe three autofocus algorithms, details the realization of those autofocus algorithms.After applying autofocus algorithms to real radar data, results show that these algorithms are very efficient.