Sparse Autofocus Method for Maneuvering Platform High-squint SAR Based on Two-dimensional Spatial-variant Motion Compensation
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摘要: 大斜视角和空间3维加速度的存在使机动平台SAR的运动误差具有明显的2维空变性，极大地增加了成像难度。为此，该文提出了一种基于2维空变运动误差估计与补偿的稀疏自聚焦方法。该方法基于Keystone变换和频域相位滤波法构造了能够校正成像参数空变性的频域近似观测算子。在自聚焦过程中，首先，构建基于频域近似观测算子的稀疏自聚焦模型并采用迭代软阈值方法(ISTA)进行求解，从而实现图像的粗聚焦和非空变运动误差的估计；然后，采用稀疏自聚焦模型估计多个子区域的精确相位误差曲线，并基于最小二乘法估计空变的运动误差参数；最后，通过对近似观测算子的修正实现空变运动误差的补偿。仿真实验验证了该方法的有效性。Abstract: The existence of high-squint angle and three-dimensional acceleration makes the motion error of maneuvering platform SAR have obvious two-dimensional spatial variability, which greatly increases the difficulty of imaging. A sparse autofocus method based on the estimation and compensation of two-dimensional spatial-variant motion error is proposed. Based on the Keystone transform and the frequency domain phase filtering method, a frequency-domain approximate observation operator is constructed to correct the spatial-variant imaging parameters. In the process of autofocus, firstly, a sparse autofocus model based on the frequency-domain approximate observation operator is constructed to focus the image roughly and estimate the non-spatial-variant motion error parameters, and the Iterative Shrinkage-Thresholding Algorithm (ISTA) is used to solve the constructed sparse autofocus model. Then, the precise phase error curves of multiple sub-regions are obtained by the sparse autofocus model and the least square method can be used to estimate the spatial-variant motion error parameters. Finally, the compensation of spatial-variant motion error is realized by correcting the approximate observation operator. The simulation results show the effectiveness of the proposed method.
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表 1 仿真参数
参数 数值 参数 数值 载频 17 GHz 地面斜视角 60° 距离带宽 300 MHz 平台高度 4 km 合成孔径时间 3 s 中心斜距 12 km 脉冲宽度 5 μs 速度 (150, 0, –30) m/s 脉冲重复频率 1 kHz 加速度 (2.2, 1.1, –1.8) m/s2 
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