Exploiting Spatial Diversity in MIMO Radars with Collocated Antennas

MIMO systems have revolutionized wireless communications resulting in unprecedented channel capacity. This breakthrough led researchers in radar as well as wireless communications communities to investigate the applicability of MIMO systems to radar. Preliminary research is showing that the full benefits of MIMO technology is realized when antenna spacing results in a decorrelated target scattering matrix. This requires antenna placement such that each receiver is observing an independent view of the target. Research is also showing that suboptimal improvements can be attained when the scattering matrix is partially correlated. This situation arises when antennas are collocated. In this work, we investigate the feasibility of MIMO Radar technology when antenna placement is quite restricted, such as in phased-array antennas. We extend the theoretical results for the correlation coefficients derived for statistical MIMO radar. We apply these results to assess the degree of decorrelation that can be achieved with Phase-Array antennas. We quantify our results as a function of antenna element spacing, frequency band and target RCS. In addition, we quantify the degree of decorrelation that is achievable by antennas that are typical in a tactical missile environment. Our results show that even when the antennas are quite small, it is possible to achieve a significant degree of decorrelation for a certain class of targets and certain frequency bands