A novel closed-form azimuth/elevation angle and polarization estimation technique using only electric dipole triads or only magnetic loop triads with arbitrary unknown spacings

This paper introduces a new closed-form ESPRIT-based algorithm for multi-source direction finding using only dipole triads or only magnetic loop triads, arbitrarily spaced at possibly unknown locations. A dipole (loop) triad consists of three identical co-located but orthogonally oriented electrically short dipoles (magnetically small loops), separately measuring all three Cartesian components of the incident electric (magnetic) field. ESPRIT exploits the polarizational but nonspatial inter-relations among the three unknown electric-field (magnetic-field) components of each source. By solving a set of nonlinear equations relating different entities in the electric-field (or magnetic-field) vector's ambiguous estimate, the signal's arrival angles and polarization states may be unambiguously estimated. Monte Carlo simulation results verify the efficacy and versatility of this scheme. This method, using only dipole triads or only loop triads, represents a simplification of Li's and Wong and Zoltowski's earlier and related direction finding schemes requiring both the six-component electromagnetic vector-sensor, each of which must consist of a dipole triad plus a co-located loop triad.