A Novel Space–Time Coding Scheme Used for MIMO-SAR Systems

Attention has been devoted to multi-input-multi-output (MIMO) synthetic aperture radar (SAR) systems in recent years. The applications of MIMO-SAR systems that involve high-resolution wide-swath remote sensing, 3-D imaging, and multi-baseline interferometry are seriously limited by the ambiguous energy introduced by the imperfect orthogonal waveforms. The ambiguous energy degrades SAR image severely, because it can be accumulated from closely spaced scatters. In order to suppress the ambiguous energy, the space-time coding (STC) scheme using the Alamouti technique has been proposed recently. However, this scheme is based on the assumption that the channel responses are constant within the consecutive transmissions. For the time-variant channel responses caused by motion errors or other factors, there will be residual ambiguous energy and “ghost targets.” In this letter, a novel STC scheme suitable for MIMO-SAR systems is proposed. The performance of the proposed scheme is immune to the time-variant channel responses. Moreover, it can get more spatial diversities to enhance the MIMO SAR imaging applications. The proposed scheme is validated by numerical simulation results.