Coherent and Noncoherent Joint Processing of Sonar for Detection of Small Targets in Shallow Water

Abstract

A coherent-noncoherent joint processing framework is proposed for active sonar to combine diversity gain and beamforming gain for detection of a small target in shallow water environments. Sonar utilizes widely-spaced arrays to sense environments and illuminate a target of interest from multiple angles. Meanwhile, it exploits spatial diversity for time-reversal focusing to suppress reverberation, mainly strong bottom reverberation. For enhancement of robustness of time-reversal focusing, an adaptive iterative strategy is utilized in the processing framework. A probing signal is firstly transmitted and echoes of a likely target are utilized as steering vectors for the second transmission. With spatial diversity, target bearing and range are estimated using a broadband signal model. Numerical simulations show that the novel sonar outperforms the traditional phased-array sonar due to benefits of spatial diversity. The effectiveness of the proposed framework has been validated by localization of a small target in at-lake experiments.

An Overview of Next-Generation Underwater Target Detection and Tracking: An Integrated Underwater Architecture

“…The method uses a passive sonar system to analyze the features of AUV. Likewise, for active sonar, a coherentnoncoherent joint processing framework is proposed in [8] to detect a small target in shallow water.…”

“…Three different types of active sonar systems are used to detect and track the target: monostatic (both transmitter and receiver are co-located), bistatic (receiver is separated from transmitter), and multi-static (one transmitter and multiple receivers). To estimate the target bearing and range with special diversity, a broadband signal model is used that has been proved in the simulation results of [8]. Passive sonar systems only provide bearing information.…”

Reference Phase Stabilizer for Distributed Underwater Sonar Systems

“…Detailed descriptions about distributed sonar system can be found in Refs. [2,3,4] and “Distributed Agile Submarine Hunting (DASH)” program disclosed by the Defense Advanced Research Projects Agency (DARPA) [5]. To accurately measure the direction of arrival (DOA) of echoed signals, all sensor nodes share a highly stable reference signal.…”