Jeffrey L. Krolik
Dept. of Elec. Eng., Duke Univ., Box 90291, Durham, NC 27708-0291
In recent work, minimum variance (MV) beamforming with sound-speed perturbation constraints (MV--SPC) [J. L. Krolik, J. Acoust. Soc. Am. 92, 1408--1419 (1992)] was proposed as a means of improving the robustness of MV matched-field source localization methods to random sound-speed profile inhomogeneities in the ocean channel. In this paper, an extension of the approach is developed that uses wave-front measurements from a source-of-opportunity to substantially improve MV--SPC beamformer performance. The proposed method consists of MV--SPC beamforming with constraints derived from the statistics of hypothesized point-source wave-front replica vectors conditioned on the measurement of a source-of-opportunity wave front at a particular point in time and/or space. Using a priori knowledge of the space-time correlation of sound-speed inhomogeneities, optimal prediction of the conditional signal wave-front correlation matrix is used to compute more precise MV--SPC beamformer constraints. The method also includes an accurate procedure for estimating a source-of-opportunity wave front in a multiple source environment. [Work supported by ONR.]