A Novel MIMO SAR Transmission Scheme for Restoring Repeated Equivalent Phase Centers

Multiple-input-multiple-output (MIMO) radar is an advanced radar system, which grows into a promising candidate for the future synthetic aperture radar (SAR) because the MIMO radar can provide more degrees of freedom (DOFs). Monostatic MIMO SARs (where transceiver channels share the same antenna array) will produce lots of repeated equivalent phase centers (EPCs) due to the same wave path, and these repeated EPCs actually have no improvement to the DOFs of the radar system, resulting in a tremendous waste of the radar resources. To this end, this article devises a novel radar framework, which is referred to as MIMO SAR with inter-pulse phase coding and multicarrier (IPCMC). The IPCMC scheme employs multicarrier and well-designed phase codes in transmitting channels, which has the advantage of increasing the DOFs in elevation. Concretely, by introducing the carrier information into the transmission-receiving spatial frequency domain, nonoverlapped spatial frequency difference curves can be obtained to further increase the DOFs in elevation. Furthermore, an advanced range ambiguity separation method based on the proposed IPCMC MIMO SAR is presented. Compared with SAR systems with different numbers of DOFs, the proposed IPCMC MIMO scheme can precisely separate more ambiguous regions, due to the increased DOFs. Finally, detailed simulation experiments are carried out to verify the efficacy of the proposed IPCMC MIMO SAR.