Maximum likelihood methods for determining the direction of arrival for a single electromagnetic source with unknown polarization

The problem of estimating the direction of arrival (DOA) of narrowband signals received from a single far-field source that transmits with an unknown polarization is addressed. The correspondence addresses both the problems of (I) estimating DOA from a sequence of snapshots having unknown but constant polarization, and also (II) estimating DOA from a sequence of array snapshots possibly having different polarizations (i.e., polarization agility). The principal results are identification of the maximum likelihood (ML) estimator of DOA for the two problems. Search for both algorithms is reduced to angle. Computational requirements are modest, and similar to those of conventional monopulse processors. Specifically the computationally-intensive eigenanalyses associated with the extended MUSIC algorithm are bypassed