基于虚拟慢时间的双基地ISAR成像算法

针对双基地角时变引起的逆合孔径雷达（ISAR）图像畸变和散焦问题，提出了一种基于虚拟慢时间的成像算法。首先，分析了双基地角时变对ISAR成像的影响机理。然后，基于图像对比度最大准则估计等效旋转中心位置，完成初次相位补偿。最后，通过虚拟慢时间构建基于非均匀虚拟采样的补偿系数矩阵，并通过方位向非均匀傅里叶变换得到目标的ISAR像。算法基于图像对比度最大准则解决等效旋转中心位置估计问题，通过虚拟慢时间消除转动相位项的高次项影响，利用非均匀傅里叶变换解决随机虚拟采样的谱估计问题。理论分析和仿真结果验证了算法的有效性和鲁棒性。

Bistatic ISAR imaging algorithm based on virtual slow time

The distortion and defocusing of bistatic Inverse Synthetic Aperture Radar (ISAR) image are induced by the time-varying bistatic angle. To solve this issue, an imaging algorithm based on virtual slow time is proposed. First, the influence mechanism of time-varying bistatic angle on ISAR imaging is analyzed. Then, the equivalent rotation center position is estimated based on the maximum image contrast criterion, completing the initial phase compensation. Finally, the compensation coefficient matrix with non-uniform virtual sampling is constructed based on virtual slow time. The ISAR two-dimensional image of the target is obtained by non-uniform Fourier transform along Doppler direction. Based on the maximum image contrast criterion, the algorithm successfully estimates the equivalent rotation center position. The influence of the quadratic phase terms is alleviated via virtual slow time, and the spectrum estimation problem of random virtual sampling is solved by non-uniform Fourier transform. Theoretical analysis and simulation results have verified the effectiveness and robustness of the algorithm.