基于三维等距球体解析模型的俯冲段大斜视SAR成像算法

当合成孔径雷达(SAR)工作在俯冲段大斜视模式时，面临着斜视角沿距离向空变、距离-方位耦合严重以及3维速度与加速度带来扰动等问题，导致回波存在着严重的距离徙动(RCM)和多普勒相位的2维空变。针对这些问题，该文构建了一种用于精确描述俯冲段大斜视SAR回波距离-方位空变特性的3维等距球体解析模型。基于该模型，提出一种去除方位空变残余高阶RCM的校正方法，并重新推导了去除多普勒相位方位空变的频域拓展非线性变标(FENLCS)方法，结合子孔径处理方式解决了SAR工作在俯冲段大斜视模式下所面临问题。理论分析和仿真结果证明，该文构建的模型对于回波的距离-方位空变特性有着更精确的描述，且所提算法具有更好的成像效果。

An Imaging Algorithm for Diving Highly Squinted SAR Based on Three-Dimensional Equidistant Sphere Analytical Model

In the case of diving highly squinted Synthetic Aperture Radar (SAR), the existence of range-dependent squint angle, severe range-azimuth coupling, three-Dimensional (3-D) velocity and acceleration produces two-Dimensional (2-D) spatial-variant Range Cell Migration (RCM) and Doppler phases. To accommodate these issues, this paper constructs a 3-D equidistant sphere analytical model to precisely reveal the range-azimuth variant property of the echo. Based on the model, an azimuth-variant residual high-order RCM correction is proposed, and the Frequency Extended NonLinear Chirp Scaling (FENLCS) is rederived to equalize the azimuth-variant Doppler phases. These two methods integrated with SubAperture (SA) processing are adopted to address the aforementioned issues faced by diving highly squinted SAR. Theoretical analysis and simulation results validate that the proposed model is capable of describing the range-azimuth spatial-variance property of echo more precisely, and better imaging performance can be acquired by this algorithm.