Polarization-Agnostic DOA Estimation With Non-Collocated Dual-Polarized Array

The non-collocated dual-polarized array alleviates the mutual coupling between the orthogonally polarized antennas. Nevertheless, the enlarged inter-element spacing may bring ambiguity issue, and the conventional direction-of-arrival (DOA) estimation algorithms may require varied processing approaches for different signal environments. For these problems, this paper first introduces two types of non-collocated array configurations called the interleaved array and the side-by-side array. The former helps to improve the aperture efficiency, and the latter can enable distributed applications. Subsequently, a polarization-agnostic DOA estimation method is proposed. In this method, firstly the low-dimensional array interpolation is performed via the joint minimization of the covariance matrix rank and a whitened residual error term. Then, both the auto- and cross-covariance matrices of the interpolated subarrays are employed to extract the signal subspace unrelated to the polarization parameters, based on which the fast direction finding algorithm is exploited. An alternating direction method of multipliers (ADMM) based solver is proposed to accelerate the array interpolation. The proposed method can handle the type of completely polarized (CP) signals, the type of partially polarized (PP) signals, the type of a spatial mixture of CP and PP signals, and the type of a temporal mixture of CP and PP signals without additional polarization-dependent processings. It is also compatible with the classical sparse array like the coprime array. Additionally, the extension to the 2D case is introduced. Numerical simulations are provided to demonstrate its superior performance in comparison to other representative approaches.