Direction finding in the presence of an intermittent interference

We consider the problem of estimating the direction of arrival (DOA) of a source in the presence of an intermittent jammer, i.e., a jammer that corrupts the signal of interest from time to time. This situation is encountered in slow frequency-hopped spread spectrum systems with partial time or partial band jamming. It has deleterious effects on the receiver performance, at least when a single antenna is used. We consider using an array of sensors to mitigate the effects of such an interference. The influence of the latter on the signal and jammer DOA estimates is studied. A general setup is introduced, and two different models are derived, depending on whether the jammer's presence indicators are considered deterministic or random. In both cases, the Cramer-Rao bounds (CRBs) are derived, and a numerical study of the CRB provides insights into the influence of the jammer's parameters. Additionally, it is shown that conventional methods such as ESPRIT can provide fairly accurate DOA estimates for this type of interference.