Unitary spherical esprit: 2-d angle estimation with spherical arrays for scalar fields

The authors consider the problem of two-dimensional (2-D) direction-of-arrival estimation of multiple plane waves incident on a spherical array. We propose a novel subspace technique that provides automatically paired source azimuth and elevation estimates relying on a spherical phase-mode excitation approach. The algorithm is remarkable for the low computational complexity and enhanced performance in correlated source scenarios by relying on a real beamspace approach, which allows forward-backward averaging. Moreover, the technique yields very accurate estimates by including spherical phase modes of different orders. This is demonstrated by comparing the mean error of the angle estimates obtained by spherical ESPRIT and the corresponding Cramer Rao bounds.