非合作星地双基地SAR成像精度分析

【作者】 阮俊冰；

【导师】 田忠；

【作者基本信息】 电子科技大学 ， 电路与系统， 2008， 硕士

【摘要】 星地双基地SAR系统是一种新的双基地SAR体制,具有作用距离远、安全性好、隐蔽性强、获取目标信息丰富、抗干扰性能好等优势。另外,由于其利用现有的SAR卫星作为发射源,使系统的整体成本降低,并且随着SAR卫星数目增加以及覆盖范围的增大,有望于将来在任意时间段内、全球任意地点上实现获取目标信息。因此,开展星地双基地SAR的理论和技术的研究,是一项适应现代信息化战争需求和现代军事技术发展趋势的课题。同时,星地双基地SAR也具有双基地SAR体制的一系列问题,主要有:空间几何布局更加灵活多样,增加了成像的复杂性;由更为复杂的运动误差和姿态误差引起相位误差;以及高精度成像更加困难等等。对于机载双基地SAR系统在上述几个问题上,目前虽然存在大量的理论研究,但涉及星地双基地SAR系统的成像理论分析和工程实现的资料和文献还很少。因此,本文首先介绍了星地双基地SAR成像质量的评估指标,为后续章节做了理论上的铺垫,然后对星地双基地SAR复杂的空间几何模型和回波模型进行分析,从工程实现的角度分析得到不同成像模式和特殊几何关系下的分辨特性;接着分析研究星地双基地SAR系统的相位同步误差,即收、发机所采用的独立频率源间的几种同步相位误差形式对成像的影响,给出了相关的限制门限及仿真结论;最后分析研究星地双基地SAR系统中卫星平台运动误差和姿态误差所引起的多普勒参数变化对成像质量的影响,由于星载SAR平台运动误差的校正问题,现有的资料和文献相对较多,且通过惯导能较好的校正误差,因此,本文着重分析姿态误差对成像质量的影响并给出仿真结论。另外,由于在外场实验时接收机是正侧视放置,而卫星平台的姿态误差会导致多普勒中心频率不为零,多普勒调频率也随着姿态误差而改变,因此,本文将通过研究从实测数据中估计多普勒参数的估计算法来校正其对成像质量的影响。本文最后简述了本系统的室内实验设计过程。并在上述理论分析和室内实验的基础上,对外场实验能否成功进行做了一些准备工作。更多还原

【Abstract】 Space-groundborne Bistatic Synthetic Aperture Radar (Bistatic SAR) system is a newly developed radar system. It has several peculiar advantages such as long operating distance, high security, anti-jammer capability etc. Moreover, the transmitter of the Spaceborne Bi-SAR system is the existing SAR satellite, so the cost of the system is less than other SAR system, and going with the increasable number of SAR satellite, it will be able to abtain rich information of targets at any time or anyplace in the world. Therefore, doing the basic and technic research of Space-groundborne Bi-SAR is one thing which suits for the need of modern war and the development of military technology.At the same time, in the Space-groundborne Bi-SAR system there are several technical problems, which affect the radar imaging, such as complicated geometrical and signal model, phase errors caused by motion errors and attitude errors, and difficulty of high resolving.Although there are plenty of basic researches on the technical problems for Airborne Bi-SAR system, few are dealing with practical realization and imaging basic researches for Space-groundborne Bi-SAR system. In this academic dissertation, several evaluative indexes of the quality for SAR imaging are introduced firstly to make a theoretical preparation for following chapters. Secondly, geometrical and echo signal model are studied for Space-groundborne Bi-SAR system. From a prototype designer’s point of view, the resolving of Bi-SAR system is proposed through systematic analysis. Thirdly, phase errors caused by transmitter’s and receiver’s frequency source are studied for the effect on imaging. The threshold constraint and simulation result put forward also. Lastly, Doppler parameter errors, which are caused by motion errors and attitude errors of satellite’s platform, are researched for how to improve the resolution of SAR’s imaging. This dissertation only emphasizes the effect caused by attitude errors, because the motion errors can emendate through Inertial Navigation System. At the end, several emulational results are obtained.Besides, radar which is embedded on platform sidelooking, but the attitude errors will cause the satellite offtracking the actual flight direction. Thereby, the Doppler centroid is not zero, and Doppler frequency rate is modifing. So it needs to be estimated from the raw echo data in order to focus commendably in azimuth’s direction.Finally, this academic dissertation is setting forth the laboratory test processes of Space-groundborne Bi-SAR system. At the base of that technical studies and laboratory test, a number of preparatory works are carried out for the imaging experiment successfully.更多还原