Two-stage multi-static passive SAR imaging with reduced complexity

In this paper, a two-stage image formation approach, which combines the Fourier and sparsity-based reconstruction strategies, is proposed to effectively process the multi-static synthetic aperture radar (SAR) data. This method exploits the block sparsity of the Fourier sampling patterns which contain a number of generally disjoint subbands in the two-dimensional spatial frequency domain. The Nyquist criterion is satisfied within each subband, whereas different subbands are sparsely distributed. In the proposed approach, the Fourier-based technique is first applied to produce coarse resolution images, which are then combined to produce a high-resolution image through the exploitation of sparse reconstruction techniques. The proposed approach yields significant improvement of the resulting SAR image over Fourier-based techniques, and offers substantial reduction of the computational complexity when compared to direct sparse reconstruction. The exploitation of block sparsity-based techniques also permits practical treatment of the angle-dependency of the scattering characteristics in SAR image construction.