Radar Space-Time Adaptive Processing

Space-time adaptive processing (STAP) is a signal processing technique that was originally developed for detecting slow-moving targets using airborne radars. The general principle of STAP is as follows. The radar transmits a train of M coherent pulses. The echoes from potential targets (and clutter) are collected at each of the N elements of an antenna array. Separate receiver chains are attached to each of the array elements. The received signals are sampled at a series of L successive ranges (i.e., distances) also referred to as range gates. STAP processing is applied to the M × N matrix of samples collected at each such range. This matrix is typically called a snapshot. The ensemble of snapshots at all successive ranges is referred to as a data cube and contains all the information available for target detection within a coherent processing interval (CPI). If the radar transmitter and receiver are located on the same platform (airplane or satellite), the configuration is called a monostatic configuration. If not, the term " bistatic " is used. In bistatic configurations, the carrying platforms are not only distinct, but they can also move independently. Although the general principles of STAP have been known since at least the 1980's, the field has seen a major regain of interest in the 1990's, mainly as a result of the significant increase in computational power. Much of the 1990's focused on three major topics of interest. The first is the application of STAP to monostatic radar platforms. The second is the design of computationally efficient adaptive methods (suboptimum methods) to reduce the computational load of the STAP processor. The third is the design of methods to mitigate barrage jammers. Throughout this period of time, investigators focused almost exclusively on uniform linear arrays (ULAs), where the elements are on a line and uniformly spaced. More recently, much of the attention in STAP has shifted to a new series of issues, which are now briefly described. (1) There is significant interest in bistatic configurations for the simple reason that they allow the receiving platform to remain covert during operation. (2) Researchers are considering arrays that go beyond ULAs, such as arbitrary 3D antenna arrays. One particular case of three-dimensional (3D) array is the conformal antenna array (CAA) that follows the surface of the carrying platform, such as the fuselage of an airplane or the side of a balloon. (3) There is a …