机载双站SAR成像算法改进及参数估计方法研究

【作者】 先丽；

【导师】 熊金涛；

【作者基本信息】 电子科技大学 ， 信号与信息处理， 2008， 硕士

【摘要】 机载双站合成孔径雷达(Airborne Bistatic Synthetic Aperture Radar—AirbornBi-SAR)是一种以飞机为平台载体,收、发平台分置的SAR系统,它具有作用距离远、抗干扰性能好、隐蔽性强、能获取丰富目标信息等特点,是现在国内外雷达系统研究的热点。由于机载双站SAR收、发分置的特点,在系统设计和信号处理的实现中会面临新的技术难题。其空间几何模型更多样化,回波信号更加复杂,因此,存在着诸如成像方法,多普勒参数估计,以及收、发同步等技术问题。本论文针对相关技术问题主要进行了以下工作:1.对常见的几种机载双站SAR飞行模式进行了几何建模,并对其回波模型、多普勒特性进行了分析;研究分析了收、发双站基线偏角、俯仰角、各自的速度以及收、发站波束中心距离与距离向、方位向分辨率的关系。2.讨论了双站SAR距离-多普勒(Rang-Doppler—RD)成像算法;分析研究了在双站斜视和双站SAR特有的基线不垂直情况下的两种改进RD算法:二次距离压缩算法和斜视成像模式算法,并通过仿真分析检验了RD算法及其改进算法各自的适用性、局限性及各自的优缺点。3.对实际飞行试验获得的实测数据分别采用双站RD算法及其改进算法进行了成像处理,并得到了较好的实测数据图像,验证了这三种算法在平飞模式下的有效性。在实测数据预处理中,分析了PRF线性同步误差的产生原因及影响,采用了基于Radon变换的PRF线性同步误差补偿方法,并通过对实测数据的处理验证了其有效性。4.从时域和频域两方面研究了多普勒质心估计方法,并对这两种情况下算法的应用情况进行了仿真和对比,分析了各自的适用条件。5.研究了几种自聚焦算法,利用这几种算法对机载双站SAR飞行试验实测数据进行了多普勒调频斜率估计和成像,验证了其在平飞模式下的适用性,并总结比较了这几种算法的优点和局限性。更多还原

【Abstract】 Airborne Bistatic Synthetic Aperture Radar (Bi-SAR) is a kind of SAR systerm whose transmitter and receiver are located on different airplanes as their platforms. It has the advantages of long detecting distance, capability of countering vulnerability, high security, ability of obtaining rich information etc., so the theoretical and experimental researches of Bistatic SAR are actively carried out in many countries and institutions.With the characteristi of separated transmitter and receiver, there will be many technic problems in system design and signal processing. The geometrical models will be more various and echo signals will be more complex. Then the technic problems such as imaging algorithms, Doppler parameters estimation, and synchronization and so on need to be solved. The main work of this thesis is shown as follows:1. Research on different geometrical models of the airborne Bi-SAR. The characteristics of echo model and Doppler characteristics are analysed. The relationship between the resolution and flight situations is discussed.2. The Bi-SAR Range-Doppler (RD) algorithm is researched, and the improved RD algorithms: Second Range Compression (SRC) algorithm amd Squint Imaging Mdoel (SIM) algorithm are used in the situations of squint model or the base line angle which is not zero. The applicabilitys of RD algorithm and its improved algorithms are verified through simulation experiments.3. Bi-SAR RD algorithm and its improved algorithms are used to process the experimental data of Bi-SAR flight experiment. The Bi-SAR images used these algorithms are generated sucessfully. The method based on Radon transform is shown to compensate the PRF linear synchronization error of the experimental data during the ex-processing.4. The Bi-SAR Doppler center estimation algorithms are studied in both time domain and frequency domain. The results of simulation are shown to analyse the advantage and limitation of each algorithm.5. The Bi-SAR autofocus algorithms are studied and used to process the experimental data of airborn bistatic SAR flight experiment. Their applicabilitys are verified under the condition of parallel flight model. The advantages and limitations of these algorithms are discussed finally.更多还原