Trajectory Inversion and Motion Compensation Method Based on Range-Doppler Domain Backprojection for Bistatic SAR

Compared to monostatic synthetic aperture radar (SAR), bistatic SAR demonstrates significant advantages in operational flexibility and anti-jamming capabilities due to its physically separated transmitter and receiver. However, this configuration also introduces significant challenges for motion compensation: the motion error dimensions increase from three to six degrees of freedom, while introducing two dimensional, strongly space variant coupling into the phase errors, thereby severely degrading the image quality. To address these challenges, this paper proposes a bistatic SAR trajectory inversion and motion compensation method based on range-Doppler domain backprojection. The core innovations of the proposed method are twofold. 1) It reveals the spectral characteristics of backprojection result in the range-Doppler domain, thereby directly obtaining the range-Doppler imaging result. This approach maximizes the utilization of platform trajectory measurement information, and avoids reliance on the constant velocity flight assumption inherent in traditional frequency domain imaging methods. 2) It derives a specific linear mapping relationship between the six dimensional trajectory motion errors and the phase errors. Subsequently, the trajectory errors of bistatic platforms are accurately inverted based on residual phases extracted from the coarse range-Doppler imaging result. After compensating the estimated motion errors, high precision bistatic SAR imaging can be realized ultimately. The effectiveness of the proposed method is validated through both simulation and airborne flight experiments.