TABLE OF CONTENTS In this chapter we focus on two space-time processors which are fully adaptive. 'Fully' adaptive means that the number of degrees of freedom as given by the number of array elements and echo pulses will be preserved in the clutter rejection process. 'Adaptive' means that clutter suppression is based in some way on the received clutter data, for instance on an estimate of the clutter covariance matrix.
Why do we need adaptive clutter suppression? In principle the space-time clutter characteristics are well known a priori through the angle-Doppler relation. However, various kinds of errors in the receiving instrument or perturbations of the flight path through platform motion may degrade the performance of non-adaptive techniques such as DPCA. For example, a comparison between adaptive and non-adaptive DPCA processing (SHAW and MCAULEY [462]) in the presence of beam squint errors reveals that adaptivity can compensate for errors in the receiver mechanism. The use of adaptive space-time filtering to compensate for various kinds of radar inherent errors has been pronounced by SURESH BABU et al. [477].
In contrast to subspace techniques (see Chapters 5, 6, 7) which exploit the subspace properties of space-time clutter data the processors discussed in the chapter are based on the full space-time covariance matrix of the available data vector space. The application of the fully adaptive space-time processor for clutter rejection has been discussed by KLEMM [238] and WARD [530, p. 57]. For small data size N, M the optimum processor...
