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Cognitive sonar for MUS for ASW. Bates, Jeffrey ;  Grimmett, Douglas ;  Van Walree, Paul ; Canepa, Gaetano; Fois, Marco ;  Stinco, Pietro ; Tesei, Alessandra. CMRE-MR-2019-007. March 2020.

This report describes some key ideas and applications of cognitive sonars for maritime unmanned system (MUS) for anti submarine warfare (ASW), highlighting the limits and the path forward. Cognitive sonars are systems based on the perception action cycle of cognition that senses the environment, learns relevant information from it about the target and the background, and then adapts the sonar sensor to optimally satisfy the needs of the mission according to a desired goal. The focus of this report is on how the information perceived by the sonar receiver on the operational environment can be exploited to modify the signal parameters of a continuous active sonar (CAS) pulse. Increasing the duty cycle of traditional pulsed active sonar (PAS) to approach that of a CAS mode is being investigated for ASW applications including littoral scenarios. CAS has the advantage that the target is continuously insonified, thereby increasing the chance of exploiting favourable target aspect and/or environmental conditions. CAS also offers the potential advantage of increasing the target update rate through sub-band processing to improve tracking performance. This report demonstrates that the higher update rate of CAS results in a lower false alarm rate at the output of the tracker, when compared with PAS against a simulated echo repeater target. A new processing technique is also presented that increases the linear frequency modulated CAS probability of detection at the contact level, while simultaneously making a measurement of the target range rate. The improved detection results are explained using a measurement of the acoustic channel.