Robust Multipath Time-Delay Estimation of Broadband Source Using a Vertical Line Array in Deep Water

摘要

A method based on delay-and-sum (DAS) of cross-correlation functions is proposed for multipath time-delay estimation of a broadband signal received by a vertical line array (VLA) in the reliable acoustic path (RAP) environment. The multipath arrivals are mainly concerned with the direct (D) and surface-reflected (SR) paths. Three types of multipath time-delays are obtained, namely, the average D-D time-delay and SR-SR time-delay between two adjacent hydrophones, and the D-SR time-delay at the first hydrophone. The proposed method has significant advantages for underwater applications. First, the D and SR arrivals are successfully separated from time-delay estimation point of view, outperforming the estimation of direction of arrival with conventional beamforming. Second, the estimations of the average D-D time-delay and SR-SR time-delay between two adjacent hydrophones occur at the diagonal line of the two-dimensional DAS outputs, facilitating the automatic detection and extraction of multipath time-delays. Third, the estimation is robust against noisy background noise due to the spatial accumulative effect. The method is applied to experimental data for explosive source at similar to 17 km range and 300 m depth, where it is shown that simple, stable, and fairly accurate multipath time-delay estimation can be made.