P065

P065 Adaptive Approach to Source Array Synthesis With Application to Shallow Water

A0155 Alexander Malekhanov Division of Hydrophysics and Hydroacoustics, Institute of Applied Physics, Russian Academy of Science

A0156 Elena Gorodetskaya Division of Hydrophysics and Hydroacoustics, Institute of Applied Physics, Russian Academy of Science

A0157 Alexander Sazontov Division of Hydrophysics and Hydroacoustics, Institute of Applied Physics, Russian Academy of Science

A0158 Nadezhda Vdovicheva Division of Hydrophysics and Hydroacoustics, Institute of Applied Physics, Russian Academy of Science

An interrelated consideration of the source array synthesis and array

signal processing in shallow-water channels is of particular interest

with applications to remote sensing, active schemes of target

detection, and acoustic communications. Similarly to deep-water

propagation [1], an intrinsic features here are (1) multimode sound

propagation, (2)signal coherence degradation induced by multiple sound

scattering in the channel, and (3) ambient modal noise [2]. These

environmental constraints stimulate one to formulate an adaptive

approach to source antenna synthesis. The term "adaptive "is used to

emphasize that the source array excitation is optimized in dependence

on statistical effects of multimode signal propagation in random-

inhomogeneous channel and ambient modal noise. Specific goal of this

optimization is to excite a signal which is appeared to be the most

effective for enhancement of the beamformer gain at a long distance

from the sources. In this paper, we present the adaptive source

synthesis under different criteria specified for the output SNR and

SNR gain at the receiving array beamformer. The optimal source

excitation and optimal beamforming are shown to be obtained by the use

of a similar technique of eigenvalue-eigenvector decomposition

associated with a statistical model of shallow-water sound propagation

[2]. An iterative algorithm is then formulated to correct the

excitation coefficients of the source array in such a way that leads

to step-by-step maximization of the beamformer performance. Numerical

examples for realistic environments from the Barents Sea for several

different sources/receivers arrangements demonstrate the expected

effect of adaptive source synthesis on the output beamformer

performance. The results give promise for development of a new

adaptive technology in underwater array systems.

[1] E.Yu.Gorodetskaya et al, Deep-water acoustic coherence at long

ranges: Theoretical predictions and effects on large-array signal

processing, IEEE J. Oceanic Eng., 1999, vol.24(2), pp. 156-171. [2]

E.Yu.Gorodetskaya et al, Coherence effects on array beamforming in

shallow water, Proc. 5th Europ. Conf. on Underwater Acoustics, ECUA

2000 (Lyon, France, 2000), pp. 1031-1036.