Conditional GLRT detection of a wideband source in the presence of a directional interference

The authors present results concerning passive detection of a source in the presence of a directional interference as well as a spatially white ambient noise. Under the assumption that the power spectral density of the signal and/or interference is unknown, different likelihood ratio test (LRT) or generalized LRT (GLRT) detectors result from different statistical models of the interference and/or desired source signals. The conditional GLRT processor (which uses the probability density function of the received signal, conditioned on the signal(s) of unknown spectrum, in the LRT) is derived, and it is shown that, for all cases of known/unknown source and/or interference power spectrum, it is basically a null steering system. The depth and the shape of the null as well as the post-beamforming temporal filter are affected by the assumed model. Expressions are presented for performance indices of the different detectors, and their dependence on the array beam pattern, as well as on the source and interference signal-to-noise ratio is explored.<>