Some Bounds on the Resolution of Multiple Sources in Passive Systems

Passive sensors are capable of resolving multiple sources based on their spectral characteristics and the time difference of arrival of source signals. The problem of resolving multiple sources when their spectra are not known a priori is discussed. A simple derivation of the Cramer-Rao lower bound on the estimation accuracy of both delays and spectral parameters is presented. Some quantitative measures of spatial-spectral resolution based on this bound are proposed.