Simultaneous Suppression of Residual Grating Lobes and Left/Right Ambiguity for Sparse Channel Forward-Looking SAR Imaging

Multichannel synthetic aperture radar (SAR) has the potential of resolving left/right ambiguity and then achieving high-resolution forward-looking imaging. However, when the sparse channel configuration is adopted, there are always residual grating lobes and left/right ambiguity in the imaging results. In this paper, a scheme of simultaneously suppressing residual grating lobes and left/right ambiguity for sparse channel forward-looking SAR imaging is proposed. Firstly, the formation of the residual grating lobes and left/right ambiguity are analyzed based on the signal model and imaging procedure of multichannel forward-looking SAR. Then, the characteristics of the differences in the position of grating lobes for the imaging results of different snapshots, and the spatiotemporal coupling characteristics of suppression of grating lobes and left/right ambiguity are explained. Next, a space-time steering matrix based on range history information is constructed, which establishes a linear mapping relationship between the space-time echo and the original scene. By solving the linear equation with a regularized iterative adaptive approach, the residual grating lobes and left/right ambiguity are suppressed simultaneously. The extensive simulation and experimental results demonstrate the effectiveness of the proposed method.