摘要
合成孔径雷达(Synthetic Aperture Radar,简称SAR)是五十年代发展起来的一种新型雷达体制,它利用合成孔径原理,突破了实孔径天线对分辨率的限制,并结合脉冲压缩技术,可以对远距离目标进行距离向和方位向两维高分辨成像。SAR能全天候、全天时地提供高分辨率的雷达图像。SAR成像已经广泛应用于军事及国民经济的许多领域。
本文研究合成孔径雷达的成像算法。论文对SAR的空间几何模型进行了分析,详细推导了SAR的距离多普勒算法、ω-k算法、Chirp Scaling算法和阶梯变换算法,并分析了各种算法的成像性能。论文主要内容概括为:
论文介绍了SAR的发展历史、现状和趋势,讲述了SAR成像算法的发展概况,分析了SAR的基本原理,包括SAR分辨特性,回波数据和回波信号的数学模型,成像处理方法以及距离徙动。
论文给出了SAR的四种距离模型,然后根据四种距离模型推导出四种RD算法、四种ω-k算法和两种CS算法,首次提出了等效斜视RD算法和单色斜视ω-k算法,最后对各种算法的性能进行了分析。
论文论述了SPECAN算法,然后针对SPECAN算法的缺陷,分析了阶梯变换算法的原理,接着详细讲解了一种适合大斜视成像的改进阶梯变换算法,即时变阶梯变换算法,最后对时变阶梯变换算法进行了仿真。
Synthetic Aperture Radar (SAR) is a new type of radar system developed since 1950's.With the principle of synthetic aperture and the pulse compression technology, it breaksthrough the resolution limitation imposed by the real aperture and two-dimensional highresolution to distant targets can be realized. SAR has evolved to satisfy a variety ofapplications for both civilian and military with its high resolution capability and possibilityof day and night operation in all weather.
This thesis focused on the imaging algorithms of SAR. First, we make researches onthe imaging geographical model of SAR, and then the Range Doppler algorithm, theω-kalgorithm, the Chirp Scaling algorithm and the Step Transform algorithm are analyzedcarefully in theory. The performances of different imaging algorithms are studied. The maincontents of the thesis are described as following:
The history, the present and the future of SAR is provided and the history of SARimaging algorithms is discussed. Then we introduced the basic principle of SAR whichincludes: the resolution theory, the mathematics model of the echo data and the echo signal,the imaging methods and the range migration.
Four range models are given, and four RD algorithms, fourω-k algorithms, two CSalgorithms are presented with the four models. Equivalent squint RD algorithm andmonochromatic squintω-k algorithm are provided by the author for the first time.Finally, the performances of these imaging algorithms are analyzed.
SPECAN algorithm is introduced. Then we discuss the Step Transform algorithmwhich can modify the deficiency of the SPECAN algorithm. Finally, the time varying StepTransform algorithm is presented which can accommodate to the high squint SAR imagingand its simulation is given.
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