Bistatic SAR Spatial-variant Motion Error Compensation Method via Joint-refocusing of Multi-subimages

Bistatic synthetic aperture radar (BiSAR) has been widely used in many fields because of its good concealment and strong anti-jamming ability. Due to the influence of atmospheric turbulence, the motion error of BiSAR is not only time-varying and space-varying, but also more complex and with higher degrees of freedom than monostatic SAR, so it is difficult to compensate the spatial-variant error of BiSAR. To cope with this problem, a spatial-variant motion error compensation method via joint-refocusing of multi-subimages for BiSAR is proposed in this paper. Firstly, a strategy for selecting multi-regions sub-images was established and sub-images with abundant ground objects were selected throughout the scene. This laid the foundation for subsequent spatial-variant motion error estimation. Secondly, the phase error of each sub-region is estimated by using the autofocus method of optimizing image sharpness, and the linear error is calculated to make the estimated error close to the real error, completing the multi-subimages phase error estimation. Then, using the relationship between the motion errors of BiSAR platforms and the phase errors of different sub-regions, the three-dimensional motion errors of the transceiver can be estimated. And based on this three-dimensional position error to compensate the transceiver position, the time-domain imaging algorithm is used to realize the spatial-variant error compensation of BiSAR, joint-refocusing is achieved, and finally the well-focused image of the whole scene is obtained. The simulation verifies the effectiveness of the proposed method.