Improving performance for matched-field processing

Abstract

Minimum energy beamforming (MEB) is frequently employed in matched-field processing (MFP) because it is optimal for the noise field prevailing at the time of measurement. However, when signal phase errors or mismatch are present, MEB is no longer optimal for signal detection. Under such conditions various methods such as reduced minimum energy beamforming (RMEB), modal beamforming, and dimension reduction have been employed. For vertical arrays, these methods have been shown to be virtually identical and to improve performance dramatically over that obtained with MEB. In this paper RMEB is extended to arbitrary array configurations and the normalizations of the ambiguity surface for various noise fields are investigated. The generalized form of RMEB is shown to produce significantly improved performance for both vertical and horizontal arrays and thus demonstrates the benefits of modal style beamforming for horizontal arrays. The improved performance was obtained for both modal and isotropic noise fields. An eigenvector decomposition of RMEB shows that the underlying cause for improved performance for both horizontal and vertical arrays is similar.