MIMO Radar, Techniques and Opportunities

MIMO techniques have been well studied for communications applications where they offer benefits in multi-path fading environments. This terminology is now appearing in the radar literature, but in several forms causing some confusion. Much of the existing work has focused on multistatic radars with sufficient spatial separation to de-correlate target RCS fluctuations, and where the data from the radars are combined incoherently. Another form of MIMO radar, closer to the communications technique, is where multiple orthogonal signals from the individual transmitter elements of a phased array are coherently combined on reception to form multiple beams. This paper presents a simple understanding of this within-aperture MIMO technique. We show how a filled array of "phantom" elements can be formed from relatively few physical elements. We explain the phantom element concept and extend it to the synthesis of various antenna array configurations, covering one, two and three dimensional geometries. The paper describes a range of waveform and signal processing options and discusses the implications of these radar capabilities