Single-hydrophone-based passive localization for vertically moving targets in shallow water

Abstract

In this article, we consider underwater passive localization for vertically moving targets in shallow water. A method that utilizes parameters derived from interference structures is introduced, which enables the implementation of both range and depth estimations for targets with a single hydrophone. Underwater moving targets radiate broadband continuous spectrum signals by forming multipath signals through interface reflections, resulting in stable interference structures in the time-frequency domain of the received signals. Ray theory is utilized to derive the trajectory equations of the interference fringes. Considering the periodic characteristics of interference structures, a specialized homomorphic filter is designed to effectively restore the peaks of the fringes to reduce localization errors. Furthermore, with a priori information on the target's initial depth, the Hough Transform is used to extract the target's location information within interference fringes formed by direct signal and surface-reflected signal. Addressing the issue of multi-peaks in parameter domain, parameter information across multiple fringes is fused. The effectiveness and robustness of the proposed method have been demonstrated through numerical simulations, lake trial, and error assessments, even when underwater environments information is not precisely known.