Estimation performance of coherent MIMO-STAP using Cramér-Rao bounds

Space-Time Adaptive Processing (STAP) is a recent technique used in airborne phased array radar to detect slow-moving targets embedded in an interference background such as jamming or strong clutter. Improved clutter mitigation by STAP enables these targets to be detected. With the use of MIMO configurations, the performance of the radar can be further enhanced, such as the angle-estimation performance and Minimum Detectable Velocity (MDV). In this paper, different coherent MIMO configurations are considered and their estimation performances are investigated in terms of the well-known Cramer-Rao bounds (CRB) which give the lower bounds of the variances of the estimators of deterministic parameters. For the same Signal-to-Clutter Ratio (SCR), the configuration that maximizes the effective number of elements gives the lowest bounds. The bounds can be further lowered without causing additional ambiguities by increasing the element spacing in certain ways.