This chapter describes the methodologies for online processing of the received radar data by a set of N antennas and M pulse repetition intervals (PRIs) for the calculation of 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. An analysis of the numerical robustness of the STAP computational schemes is presented when the CORDIC (coordinate rotation digital computer) algorithm is used to compute the QRD and the IQRD. Benchmarks on general purpose parallel computers and on a VLSI (very large scale integration) CORDIC board are also presented.