Detection of multiple unresolved Rayleigh targets using quadrature monopulse measurements

When the returns from two or more targets interfere (i.e., the signals are not resolved in the frequency or time domains) in an amplitude comparison monopulse radar system, the direction of arrival estimate indicated by the monopulse ratio can wander far beyond the angular separation of the targets. The failure to detect the presence of the interference can be catastrophic to the performance of the tracking algorithm. The detection of the presence of unresolved Rayleigh targets is considered in the paper. A Neyman-Pearson detection algorithm is developed with density functions that are conditioned on the measured amplitude of the target echoes, which will be shown to define the statistics of each measured monopulse ratio. The algorithm uses both the in-phase and quadrature portions of the monopulse ratios. Receiver operating characteristic curves are given along with simulation results that illustrate the application of the algorithm.