The Adaptive Likelihood Ratio Detector

A search for a theory of optimum adaptive detectors leads instead to a theory of adaptive realizations for optimum (likelihood ratio) detectors. The virtue of adaptation is not in achieving breakthroughs in performance. The real role of adaptation is that certain levels of performance that are achievable by both adaptive and nonadaptive detectors may be achievable with cheaper or smaller equipments if they are adaptive. The paper ends with a short discussion of implementation of the design rules furnished by likelihood‐ratio theory.