Synthetic aperture imaging using a randomly steered spotlight

In this paper, we develop a new approach to synthetic aperture imaging inspired by recently developed compressive sensing (CS) methods. Our approach modifies the beam steering pattern of conventional sliding spotlight-mode systems and randomizes it such that with each pulse the beam illuminates a different, randomly chosen, part of the imaged area. The randomization allows the acquisition of the area of interest with a significantly larger effective aperture compared to the conventional sliding spotlight mode and, therefore, with significantly larger resolution. The reconstruction estimates the signal using a model that combines a sparse and a dense component. This model captures the structure of SAR images better than conventional sparse models, typically used in CS, and provides superior reconstruction performance. Our experimental results demonstrate that the proposed randomly steered spotlight array can improve imaging resolution, as measured by the reconstruction SNR and the phase error, without compromising the covered area size.