System architectures and algorithms for radar imaging by MIMO-SAR

The multi-input / multi-output (MIMO) principle is well known for communication applications, whereas at least the name dasiaMIMOpsila is relatively new for radar applications. Nevertheless, the principle has been analyzed and used in a few examples since the early 80s or even before. A MIMO-radar is characterised by a number N of transmitting and a number M of receiving antennas forming N times M Tx/Rx pairs where each propagation path from the nth transmit antenna to the object to the mth receive antenna is made available to the signal processing. This can be achieved by temporal multiplexing, spatial coding and/or orthogonal waveforms. A further step is to transfer this technique to the SAR case. Additionally, the whole array is moving, SAR processing can be applied. Possible geometries of MIMO-SAR are along track arrays (reduction of azimuth-ambiguities, moving target indication, super resolution) or across track arrays (reduction of elevation-ambiguities, interferometry, 3D down-looking SAR). In this paper, some aspects of moving MIMO-arrays for SAR will be addressed.