Real-time STAP techniques

This paper describes methodologies for the on-line processing of the received radar data by a set of N antennas and M pulse repetition intervals (PRIs) for the derivation of the space-time adaptive (STAP) filter output. The numerically robust and computationally efficient QR-decomposition (QRD) is used to derive the so called MVDR (minimum variance distortionless response) and lattice algorithms; the novel inverse QRD (IQRD) is also applied to the MVDR problem. These algorithms are represented as systolic computational flow graphs. The MVDR is able to produce more than one adapted beams focused along different angular directions and Doppler frequencies in the radar surveillance volume. The lattice algorithm offers a computational saving; its computational burden is O(N²M) in lieu of O(N²M²). A comprehensive analysis of the numerical robustness of the STAP computational schemes is presented when the CORDIC algorithm is used to compute the QRD and the IQRD. Benchmarks on general purpose parallel computers and on a VLSI CORDIC board are presented. The paper introduces the STAP problem and the basic systolic algorithms to reach real time adaptation. The lattice and its generalization (vectorial lattice) for wideband problems are discussed including experiments of mapping the basic triangular systolic array onto general purpose parallel computers. The use of VLSI CORDIC board is also described and a perspective is given for future research and experimental work