Acoustic Clutter Removal

Abstract

With the widespread availability of commercial and recreational underwater vehicles, maintaining underwater security in ship channels and harbors is more challenging than ever before. Acoustic clutter from moored and moving vessels, bottom objects, and docks make threat detection technically difficult and costly. The objective of this article is to demonstrate how basis vector properties of maximum length sequences may be used in a bistatic geometry to coherently subtract clutter from the received signal, thereby transforming a difficult signal-in-clutter detection problem into a more tractable signal-in-noise detection problem. Signal processing steps are described in Part 1. Steps that are critical, or have not been well documented previously, are in italics. In Part 2, the performance of a notional traffic monitoring system with underwater coverage is simulated for a segment of the Hong Kong Ship Channel. Although the focus of this work is on underwater applications, the algorithm may apply in other situations where small targets must be detected in the presence of much larger objects. Active sonar, medical imaging, and ground penetrating radar are among the potential applications.