Closed-form direction finding and polarization estimation with arbitrarily spaced electromagnetic vector-sensors at unknown locations

This paper introduces a new closed-form ESPRIT-based algorithm for multisource direction finding and polarization estimation with arbitrarily spaced electromagnetic vector-sensors whose three-dimensional (3-D) locations need not be known. The vector-sensor, already commercially available, consists of six colocated but diversely polarized antennas separately measuring all six electromagnetic-field components of an incident wavefield. ESPRIT exploits the nonspatial interrelations among the six unknown electromagnetic-field components of each source and produces from the measured data a set of eigenvalues, from which the source's electromagnetic-field vector may be estimated to within a complex scalar. Application of a vector cross-product operation to this ambiguous electromagnetic-field vector estimate produces an unambiguous estimate of that source's normalized Poynting vector, which contains as its components the source's Cartesian direction cosines. Monte Carlo simulation results verify the efficacy and versatility of this innovative scheme. This novel method maybe considered as a simplification and a refinement over Li's (1993) work.