Unambiguous directions of arrival estimation of coherent sources using acoustic vector sensor linear arrays

This work investigates the problem of estimating directions of arrival (DOAs) of coherent sources without the left-right ambiguity by acoustic vector sensor linear arrays. Toeplitz matrices obtained from vector sensor cross covariance matrices are summed to obtain a new matrix with vector sensor directivities as weights. In this way, the proposed method restores the rank of the equivalent signal subspace and eliminates 2π ambiguous DOA information of sources. A robust technique is also developed to improve its performance degradation because of the velocity sensor gain uncertainty during unit conversion, such as imprecise measurements of the sensor sensitivities and the product of the water density and sound speed in the water. The methods can be implemented as a preprocessing stage before applying beamformers, such as multiple signal classification and MVDR. Theoretical analyses show that comparing with existing preprocessing techniques, the proposed methods can fully resolve the coherent sources without the left-right ambiguity while keeping the effective array aperture, and even applicable to the case of closely spaced coherent sources. Their effectiveness and performances are conducted via simulations.