TABLE OF CONTENTS The received radar signals from targets are always superposed with the receiver noise and other disturbing signals, such as signals received from jammers, hostile noise transmitters trying to blind our radar, and echoes from clutter reflectors, that is from ground or fixed targets, trees, vehicles or meteorological scatterers. These disturbing signals are always randomly fluctuating by the nature of their origin. Radar targets, such as airplanes or missiles, are generally very complex and composed of multiple single reflection centres. The targets' movement results in varying phase relationships of the partial echoes from the multiple complex reflection elements. The superposition of all these partial echoes yields therefore a fluctuating resultant target echo.
The main task of a radar system is the detection of targets. In other words, for each resolution cell in space we have to decide target present or no target present . Because of the fluctuating nature of the signals this task cannot be performed with absolute certainty, but only with a limited percentage or probability of correct decisions. Of course we want to make as many correct decisions as possible according to the underlying situation. That is, we want to detect a target if it is really present, and we want to deny a target if that target is really absent and there is only noise. So we are led quite naturally to the field of statistics or, more precisely, to the need for a statistical description of radar signals and the assessment...
