LEAST-SQUARES APPROXIMATION FOR THE DELAYS USED IN FOCUSED BEAMFORMING

A novel approximation for the delays used in focused beamforming is pr esented that is based on weighting the terms of the conventional Fresn el approximation. The objective is to enlarge the validity region of t he Fresnel approximation in order to investigate wider scanning region s. A least-squares solution provides the exact weight values by the mi nimization of the mean-square error computed over the desired scanning region and on the basis of the array geometry. The attractive results obtained by applying the proposed approximation to a Linear array are presented. (C) 1998 Acoustical Society of America. [S0001-4966(98)065 06-0].