基于级数反演的双基前视高机动平台SAR成像算法

双基前视高机动平台合成孔径雷达BFHM-SAR是一种新型合成孔径雷达成像模式,可实现高机动平台末端俯冲阶段全程二维高分辨成像。由于BFHM-SAR中收发平台沿曲线轨迹运动且均具有较大的速度和加速度,导致双基距离历程中存在双根号下高阶项的问题。此外,该构型相较于单/双基直线轨迹SAR,存在更为严重的距离徙动问题。针对上述缺陷,文中首先在时域对距离走动量进行校正以减少二维耦合量,然后在斜距精确高阶近似的基础上结合级数反演思想推导出信号的二维频谱,在距离频域-方位多普勒域进行剩余的距离走动和距离弯曲的校正,最后完成二维脉冲压缩,在实现高分辨成像。文中对该构型下特殊的方位向聚焦深度的问题也进行了具体分析,仿真实验结果验证了成像算法的正确性和可行性。

Imaging Method for Bistatic Forward-Looking High-speed Maneuvering-platform SAR Based on Series Reversion

BFHM-SAR is a new and special imaging mode, which performs 2D imaging during the whole terminal diving period of high speed maneuvering platform. In the BFHM-SAR, the transceiver platform moves along different curve trajectories and has great velocities and accelerations, which leads to the problem of high-order terms under the double root and more serious range cell migration in the double-base distance history. In addition, this configuration has a more serious distance migration problem than monostatic or bistatic SAR. This study firstly corrected the range walk in time domain to reduce the two dimensional coupling, and then derived the two-dimensional frequency spectrum by the method of series reversion based on the accurate approximation of slant range in high order. The remaining rang cell curvature was corrected in range frequency azimuth Doppler domain and the high resolution imaging was completed after the pulse compression in both range and azimuth directions. In addition, focus depth in azimuth direction in this special configuration was analyzed in detail. Finally, the validity and feasibility of the proposed approach were verified with the simulation results.