Multiple-Input Multiple-Output Circular SAR

Interest on circular and multicircular SAR acquisitions has been increased in the past few years due to the inherent potentials they provide, e.g., full 3-D reconstruction and subwavelength resolution. However, one main limitation is the size of the spotlighted region, which is basically defined by the range ambiguities, the pulse repetition frequency (PRF), and the minimum half-power beamwidth (HPBW) in the range and azimuth directions. This paper introduces multiple-input multiple-output (MIMO) techniques in order to tackle this limitation, thereby being able to extend the applications of CSAR to much wider areas. The basic principle of the proposed solution is based on three methods, namely scan-on-receive (SCORE), multi-channel reconstruction in azimuth (MCRA) and the use of orthogonal waveforms for quad-polarized systems. The impact and dependency of the PRF, HPBW and the range ambiguities is also investigated.