Linear Dipole Array With Element Rotation for Enhanced DOA and Polarization Estimation

The linear dipole array (LDA) with the same elemental orientation is polarization insensitive and can only perform 1-D direction-of-arrival (DOA) estimation. While by appropriate element rotation, the LDA becomes sensitive to polarization and has the potential to perform 2-D DOA estimation. In this article, the information perception principle of LDA is explored, and the elemental orientations are optimized for enhanced DOA and polarization estimation. First, the polarization diversity of the LDA is quantified by an analytical polarization sensitivity (PS) factor. The PS factor is larger than zero for the LDA with element rotation, revealing it is capable of polarization estimation. Then, it is proven that the LDA containing three or more kinds of 2-D elemental orientations can perform ambiguity-free 2-D DOA and polarization estimation, apart from vertically linear polarization. Also, the Cramer-Rao bound (CRB)-based optimization criteria of element rotation for isotropic DOA estimation and optimal polarization estimation are presented. Moreover, a modified dimension-reduction MUSIC algorithm is developed, significantly improving the resolution performance of parameter estimation. Simulation results validate the ambiguity-free parameter estimation ability and the enhanced DOA and polarization performance of the LDAs with optimized elemental orientations.