A superresolution wide null beamformer for undersampled signal reconstruction in SIMO SAR

Abstract

With single-input single-output (SISO) SAR systems, employing a single transmitter and receiver beam, there exists ahigh resolution, wide swath contradiction. However, by using multiple receiver beams and employing array processing techniques, this contradiction can be overcome, allowing greater flexibility anda wider range of application requirements to be met. In this paper the use of single-input multiple-output (SIMO) SAR systems forovercoming this contradiction is of interest, and a novel beam-former is proposed for processing in the cross-range direction. Inorder to fully describe the system, the array manifold vector is utilized, which is a key concept in the design of the beamformer. In particular, this beamformer is a superresolution beamformer ca-pable of forming wide nulls using subspace based approaches andallows the suppression of ambiguities in multiple sets of received under sampled SAR data in the cross-range direction and reconstruction of the Doppler spectrum to form a single unambiguous set of SAR data. Compared to the existing reconstruction algorithm, only a single weighting vector is required for a block of ambiguous Doppler frequencies compared to a weight vector requiredfor each ambiguous Doppler frequency. The capabilities of the proposed beamformer are shown to give an improved performance inambiguity suppression via computer simulation studies in a representative maritime environment.