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星机联合前视双基地SAR成像原理及算法研究
【作者】 叶伟；
【导师】 张晓玲；
【作者基本信息】 电子科技大学 ， 信号与信息处理， 2011， 硕士
【摘要】 由于双基地合成孔径雷达(Bistatic Synthetic Aperture Radar,简称BiSAR)具有收/发分置的特殊系统结构,通过设计合理的空间布局,可以实现对接收机正前方区域的高分辨成像,从而有效的解决单基地SAR系统无法前视成像的盲区问题。星机联合前视双基地SAR(Spaceborne/airborne Forward-looking Bistatic SAR,简称SA-FBiSAR)采用星载平台作为发射机,机载平台作为接收机,是双基地SAR系统新的应用方面,它具有更灵活的系统、更大的观测范围等优势,在飞机自主导航,自主着陆和精确打击等民用和军事领域都具有广阔的应用前景,该系统正成为当前遥感成像领域的研究焦点。作为新的研究热点,前视双基地SAR的各方面研究都还处于初级阶段,尤其是星机联合前视双基地SAR这样典型的移变系统,在成像机理、成像算法等方面刚刚起步。已有的一些算法都是针对非移变模式的前视双基地SAR系统;对于星机联合前视双基地SAR移变系统,情况更复杂,目前还没有适用的高效成像算法。本文针对星机联合前视双基地SAR的系统特性,主要进行了回波模型、点目标响应函数、分辨特性、工作模式以及成像算法等方面的研究,主要工作包括:1.建立了星机联合前视双基地SAR的空间几何模型和回波模型,分析了星机联合前视双基地SAR系统成像的可行性,并从合成孔径时间、多普勒特性和分辨率特性的角度比较了不同飞行模式对系统性能影响,为后续的算法研究提供了理论指导;2.推导出了适用于星机联合前视双基地SAR系统的距离历史近似表达式。针对星机联合前视双基地SAR系统聚焦成像所需解决的问题,对基于空域展开的距离历史近似表达式进行了合理的扩展,推导得到了相适应的距离历史近似表达式,为后续的成像算法奠定了基础;3.建立了星机联合前视双基地SAR二维频谱模型。根据推导的距离历史近似表达式,提出了相应的距离徙动校正方法,并推导得到了相应的二维频谱模型;4.提出了一种适用于星机联合前视双基地SAR的成像算法。根据所建立的二维频谱模型,提出了相适应的聚焦算法,并结合近似表达式的空域特性提出了相应的畸变校正方法。
【Abstract】 Because of the separation between transmitter and receiver platform, bistatic synthetic aperture radar (BiSAR) can image the forward-looking terrain of receiver platform with reasonable space arrangement, so can effective solve the problem that monostatic SAR can’t image the forward-looking terrain. Spaceborne/airborne forward-looking bistatic SAR (SA-FBiSAR) use spaceborne as transmitter and airborne as receiver, this system has more flexible system and greater range of observations, so it can be widely used both civilly and militarily, such as autonomous navigation, autonomous landing and precision strike etc. SA-FBiSAR is becoming the research focus of remote imaging field.As a new research focus, the most theories of SA-FBiSAR are not completed. There is not yet a efficient algorithm for SA-FBiSAR.This dissertation mainly researches echo model, point target response function,resolution characteristics, flight patterns and imaging algorithm for SA-FBiSAR. The main works of dissertation are as follow:1. Established the geometric model and echo model of SA-FBiSAR, and compared the impact of different flight patterns on system performance with synthetic aperture time, Doppler characteristic and resolution characteristics. Then analysis the feasibility of SA-FBiSAR system;2. Reasonable extend the approximate expression of range history based on space domain expansion. Deduced the new approximate expression of range history which is suitable for SA-FBiSAR system;3. According to the new approximate expression, proposed corresponding range migration correction method and 2-D spectrum model of SA-FBiSAR;4. According to the 2-D spectrum model, proposed corresponding imaging algorithm and distortion correction method based on spatial characteristics of approximate expression.