Shallow water single mode excitation using feedback control

Abstract

This work presents an adaptive algorithm for exciting a single mode in the shallow water acoustic waveguide. Previous efforts have focused on laboratory waveguides using pre-computed weights for the source array based on precise prior knowledge of the channel [Clay and Huang, J. Acoust. Soc. Am. 67, 792–794 (1980), Gazanhes and Garnier, J. Acoust. Soc. Am. 69, 963–969 (1981)]. In contrast to these open-loop systems, the algorithm presented here uses a reference receiver array to implement a closed-loop feedback control system. The channel is characterized through an effective coupling matrix relating the source weights to the coefficients of the excited modes. The algorithm iterates between estimating the coupling matrix from the reference observations, and determining the source array weights from the estimated coupling matrix. Results from detailed simulations using actual sound-speed and bottom parameters indicate this approach allows the algorithm to adapt and compensate for environmental mismatch and some time-dependent fluctuations.