Autofocus Back Projection Method Based on Time-Frequency Information of a Single Point for Airborne SAR with Nonlinear Trajectory

Due to the limited accuracy of the navigation system, the deviation between measured trajectory and real trajectory of the radar platform deteriorates the focusing quality of the synthetic aperture radar (SAR) image. Therefore, a time domain autofocus algorithm that can effectively integrate with precise motion trajectory becomes the key to compensate for motion error. In this paper, an autofocus back projection (BP) algorithm based on time-frequency information of a single point is proposed to compensate for motion error. Considering the different influences of each dimension on slant range, this approach simplifies the three-dimensional (3D) motion trajectory errors of SAR into one dimension. By approximating the trajectory in this manner, the method integrated with the BP algorithm improves the quality of image focusing. Simulation and experimental results verify the effectiveness of the proposed method.