High-Resolution and Wide-Swath Imaging of Spaceborne SAR via Random PRF Variation Constrained by the Coverage Diagram

There is an inherent tradeoff between range swath width and azimuth resolution in the traditional spaceborne single-channel synthetic aperture radar (SAR). The range swath can be extended with reduced pulse repetition frequency (PRF), but this leads to the decrease of the azimuth resolution of SAR images. It is difficult for traditional SAR imaging methods that follow the Nyquist sampling theorem to obtain high-resolution and wide-swath imaging results simultaneously. Considering the influence of transmit pulse occlusion and the nadir echo on the selection of PRF in spaceborne SAR, a random PRF variation pulse transmission pattern that is constrained by the coverage diagram is designed in this article for wide-swath imaging. The minimum interval length between adjacent transmitted pulses is set to be larger than the Nyquist sampling interval, thus offering the capability to widen the range swath of spaceborne SAR imaging results. Then, the fast iterative shrinkage thresholding-like algorithm (FISTA-like) is performed on the nonuniformly sampled data to achieve sparse reconstruction of the high-resolution imaging results. Compared with the existing SAR imaging methods, the proposed method realizes high-resolution and wide-swath imaging for spaceborne single-channel SAR with lower hardware implementation difficulty. Simulations and experiments on measured spaceborne SAR data demonstrate the effectiveness of the proposed method.