Introduction to space-time adaptive processing

Space-time adaptive processing (STAP) is an innovative tool for use with coherent phased array radar systems which is useful whenever the received signals (target and interference) are functions of both space and time. A prominent example is the clutter suppression in air and spaceborne MTI radar. In this tutorial paper the main features of airborne clutter are summarised. The platform motion causes clutter returns to be Doppler shifted so that the total of clutter arrivals exhibits a motion induced Doppler bandwidth. Airborne clutter is either characterised by the eigenspectra of the space-time covariance matrix or by the azimuth-Doppler spectra. These spectra demonstrate the potential of slow target detection before a Doppler coloured clutter background through space-time adaptive processing. Eigenspectra give an indication of the potential of subspace processing techniques which may lead to solutions for real-time on-board operation. Certain effects such as multiple-time-around clutter, clutter fluctuations, and system bandwidth, may degrade the detectability of slow targets