Focus Improvement for High-Resolution Highly Squinted SAR Imaging Based on 2-D Spatial-Variant Linear and Quadratic RCMs Correction and Azimuth-Dependent Doppler Equalization
Focus Improvement for High-Resolution Highly Squinted SAR Imaging Based on 2-D Spatial-Variant Linear and Quadratic RCMs Correction and Azimuth-Dependent Doppler Equalization
复制标题
基于二维空间变化线性和二次 RCM 校正和方位角相关多普勒均衡的高分辨率高斜视 SAR 成像焦点改进
DOI：
10.1109/jstars.2016.2569561
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发表时间：
2017-01-01
影响因子：
5.5
通讯作者：
Tan, Xiaoheng
中科院分区：
文献类型：
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作者：
Li, Dong;Lin, Huan;Tan, Xiaoheng
在高分辨率高斜视合成孔径雷达（SAR）成像的情况下，线性距离单元迁移（RCM）校正和固有的距离相关斜视角的结果产生二维（2-D）空间变化的RCM和方位相关的多普勒参数（即，高度变化的多普勒中心和频率调制率），这使得高度斜视的SAR成像困难。然而，大多数现有的算法未能考虑这些问题。为了获得高质量的SAR图像，在这项研究中，二维空间变化的RCM和方位相关的多普勒参数进行了研究。首先，使用参考距离线性RCM校正（RCMC）来去除大部分线性RCM分量，并减轻2-D谱的距离-方位耦合。然后，在方位时间维，设计了一种新的扰动函数，用于扩展非线性调频定标（CS）（ENLCS）算法，克服了方位相关的RCM，实现了多普勒参数的均衡。为了消除固有的距离相关的RCM和由距离相关的斜视角引起的线性RCM，提出了一种新的尺度函数的改进CS（MCS）算法，并对剩余的RCM采用批量RCMC和二次距离压缩（SRC）进行补偿。利用所提出的ENLCS和MCS操作，实现了2-D空变RCMC和方位相关多普勒均衡。高分辨率大斜视SAR的仿真数据实验结果表明了该算法的上级性能。
The results of the linear range cell migration (RCM) correction and inherent range-dependent squint angle in the case of high-resolution highly squinted synthetic aperture radar (SAR) imaging produce two-dimensional (2-D) spatial-variant RCMs and azimuth-dependent Doppler parameters (i.e., highly varying Doppler centroid and frequency modulation rates), which make highly squinted SAR imaging difficult. However, the most existing algorithms failed to consider these problems. To obtain high-quality SAR image, in this study, both the 2-D spatial-variant RCMs and the azimuth-dependent Doppler parameters are studied. First, a reference range linear RCM correction (RCMC) is used to remove the most of the linear RCM components and to mitigate the range-azimuth coupling of the 2-D spectrum. And then, in the azimuth time dimension, a new perturbation function is designed in the extended nonlinear chirp scaling (CS) (ENLCS) algorithm to overcome the azimuth-dependent RCM and to equalize Doppler parameters. To remove both the inherent range-dependent RCM and the linear RCM caused by the range-dependent squint angle, a modified CS (MCS) algorithm with a new scaling function is proposed, and for the residual RCMs, a bulk RCMC and second range compression (SRC) are utilized to compensate them. With the proposed ENLCS and MCS operation, the 2-D spatial-variant RCMC and the azimuth-dependent Doppler equalization are, thus, achieved. The experimental results with simulated data in the case of the high-resolution highly squinted SAR demonstrate the superior performance of the proposed algorithm.