高分辨率机载SAR信号处理研究

【作者】 刘月花；

【导师】 荆麟角；

【作者基本信息】 中国科学院电子学研究所 ， 通信与信息系统， 2001， 硕士

【摘要】 综合孔径雷达（SAR）是自五十年代发展起来的一种新型对地观测手段，获取高分辨率和超高分辨率机载SAR图像是当今SAR发展的重要方向之一。本文主要了研究SAR信号处理中的两部分内容：成像算法和自聚焦算法。并把它们应用于处理实际数据，得到了正确结果。 首先引言从多个角度解释SAR的基本概念，介绍SAR的特点和应用。 论文第二章从脉冲压缩和合成孔径天线角度对SAR的基本原理进行分析。第三章在基本原理的基础上给出成像算法的具体实现步骤，结合中科院电子所的L-SAR数据，计算了合成孔径雷达的距离向分辨率和方位向分辨率。经成像处理后得出雷达图像。 理想情况下，SAR回波多普勒信号是线性调频信号，采用合成孔径原理提高方位向成像分辨率。然而，在实际系统中，回波信号总存在着不受欢迎的相位误差。本文详细分析了相位误差对机载SAR图像的影响，这些相位误差在成像处理中将以各种形式降低图像的质量，如几何畸变、分辨率降低、对比度下降、出现虚假目标以及信噪比降低等。 获取高分辨率SAR图像的关键是包括自聚焦算法在内的运动补偿，自聚焦技术通过补偿回波信号中的相位误差来获得高的聚焦精度。本文讨论了三种自聚焦算法，并详细介绍了各自聚焦算法的具体实现步骤。 将自聚焦算法用于处理实际数据改善了图像质量，验证了他们的有效性。更多还原

【Abstract】 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.更多还原