A Novel SAR Ground Maneuvering Target Imaging Method Based on Adaptive Phase Tracking

Ground-moving targets with complex motions often appear seriously dislocated and smeared in synthetic aperture radar (SAR) imagery due to noncooperative motion. Refocusing such targets in SAR is challenging because of unknown motion parameters. In this article, a novel SAR moving target imaging method based on adaptive phase tracking (MTIm-APT) is proposed. First, the Hough transform (HT) and the second-order keystone transform (SOKT) are performed to correct the range migration. Second, the Doppler phase can be adaptively tracked based on the improved extended Kalman filter (EKF). With the tracked Doppler phase, the motion parameters required for moving target imaging is estimated. Finally, the moving target is well-focused after motion parameters compensation since the high-order Doppler phase errors are efficiently eliminated. Unlike existing research that only considers the second- or third-order Doppler phase, the proposed method considers higher order Doppler parameters which can be simultaneously estimated, thus eliminating the error propagation effect. More importantly, due to the suboptimal filtering characteristics of EKF, the proposed method maintains excellent imaging performance at a lower signal-to-noise ratio (SNR) than classical PGA. On the other hand, our method has a certain advantage in computational efficiency. Both simulated and real data processing results are provided to validate the feasibility and effectiveness of the proposed SAR MTIm-APT method.