Fast m-sequence transform for quasi-backscatter sonar in fisheries and zooplankton survey applications

Existing acoustic systems commonly used in fisheries and zooplankton surveys are based on pulsed perturbation technique. This work applies binary maximum-length sequences (MLS) as periodic perturbation signals for sonar systems. Using MLS of pseudo-random nature, much higher signal-to-noise ratio (SNR), while keeping a similar spatial resolution as that using pulsed perturbation can be obtained. A fast algorithm, exploiting the fast Hadamard transform, is implemented for an efficient post-processing of target responses. After a brief introduction of MLS fundamentals and a fast m-sequence-based algorithm, this paper will discuss preliminary experimental results conducted in underwater environment using an experimental model.