Performance improvement for constellation SAR using signal processing techniques
Performance improvement for constellation SAR using signal processing techniques
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DOI：
10.1109/taes.2006.1642562
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发表时间：
2006-04-01
影响因子：
4.4
通讯作者：
Liao, Guisheng
中科院分区：
文献类型：
--
作者：
Li, Zhenfang;Bao, Zheng;Liao, Guisheng
星载合成孔径雷达（SAR）的一个新概念-星载小系统星座是近年来提出的。在该实施方案中，几个编队飞行的小卫星合作执行多个空间任务。研究了利用星载SAR系统星座实现高分辨率大面积SAR图像和良好的地面动目标指示（GMTI）性能的可能性。特别地，我们关注由这种特定的SAR系统引入的问题，例如多普勒模糊度、卫星阵列的高度稀疏性和阵元误差。提出了一种结合传统SAR成像算法的空时自适应处理（STAP）方法，可以在一定程度上解决这些问题。该方法的主要思想是利用基于STAP的方法来克服低脉冲重复频率（PRF）引起的混叠效应，从而从接收回波中提取出无模糊的方位宽（全）谱信号。在此操作之后，可以应用常规SAR数据处理工具来完全聚焦SAR图像。该方法可以同时实现宽场景的高分辨率SAR成像和GMTI，具有较高的效率。为了获得阵元误差，提出了一种基于杂波回波角度和多普勒模糊度分析的阵列自校准方法。分析了卫星编队优化问题，提出了一种基于平台速度/脉冲重复频率的编队优化准则。给出了一种方法，使得几乎任何给定的稀疏阵列结构都可以通过轻微地调整PRF来满足该准则。仿真结果验证了所提方法的有效性。
A new concept of spaceborne synthetic aperture radar (SAR) implementation has recently been proposed-the constellation of small spaceborne SAR systems. In this implementation, several formation-flying small satellites cooperate to perform multiple space missions. We investigate the possibility to produce high-resolution wide-area SAR images and fine ground moving-target indicator (GMTI) performance with constellation of small spaceborne SAR systems. In particular, we focus on the problems introduced by this particular SAR system, such as Doppler ambiguities, high sparseness of the satellite array, and array element errors. A space-time adaptive processing (STAP) approach combined with conventional SAR imaging algorithms is proposed which can solve these problems to some extent. The main idea of the approach is to use a STAP-based method to properly overcome the aliasing effect caused by the lower pulse-repetition frequency (PRF) and thereby retrieve the unambiguous azimuth wide (full) spectrum signals from the received echoes. Following this operation, conventional SAR data processing tools can be applied to focus the SAR images fully. The proposed approach can simultaneously achieve both high-resolution SAR mapping of wide ground scenes and GMTI with high efficiency. To obtain array element errors, an array auto-calibration technique is proposed to estimate them based on the angular and Doppler ambiguity analysis of the clutter echo. The optimizing of satellite formations is also analyzed, and a platform velocity/PRF criterion for array configurations is presented. An approach is given to make it possible that almost any given sparse array configuration can satisfy the criterion by slightly adjusting the PRF. Simulated results are presented to verify the effectiveness of the proposed approaches.