This work investigates the detection of non-cooperative underwater acoustic pulse signals at low signal-to-noise ratio (SNR). A variable scale relative entropy (VSRE) pulse signal detection scheme is proposed. Different from conventional relative entropy (RE) method where an observation sequence is processed at a given scale for detection, the proposed scheme performs the processing at multiple different scales. As a result, the original RE difference vector becomes a RE difference matrix, each column corresponding to a particular scale. Before a decision is made, the VSRE difference matrix is post-processed for improved fidelity. The non-zero elements of the resulting VSRE difference matrix are divided into groups, each corresponding to a pulse signal, based on their occurrence times within the observation sequence. Within each group, the one with the maximum RE difference is chosen to determine the exact appearance time and duration of the pulse signal. The performance gain of the VSRE detector over existing RE detector has been verified by both simulation and at-sea experimental results. INDEX TERMS Non-cooperative detection, underwater acoustic pulse signals, variable scale relative entropy.
Near-field interference suppression for a towed linear array (TLA) is investigated in this paper. The existing eigencomponent association (ECA) scheme and multiple signal classification interference suppression (MUSIC-IS) scheme require the prior information of a target bearing in order to achieve satisfactory performance. To improve this, we propose the use of an enhanced ECA (EECA) scheme that achieves interference suppression in a non-cooperative scenario. It identifies non-target eigenvectors by scanning the tail direction zone of the TLA. With the non-target-only eigenvectors subtracted, the beam power spectrum of the EECA manifests null troughs at the target bearings. Numerical simulations show the superiority of the EECA method. This method can effectively suppress strong interference without prior information, capture a target even at a low signal-to-interference (SIR) level of −25 dB, and obtain dozens of dB processing gains compared to the ECA and MUSIC-IS.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.