Experimental Comparison of High Duty Cycle and Pulsed Active Sonars in a Littoral Environment

Military sonars must detect, localize, classify, and track submarine threats from distances safely outside their circle of attack. However, conventional pulsed active sonars (PAS) have duty cycles on the order of one percent which means that 99% of the time, the track is out of date. In contrast, high duty cycle sonars (HDC) have duty cycles approaching 100% which enable near-continuous updates to the track. If one can overcome technical challenges such as the high dynamic range required by the receiver, then HDC should significantly improve tracking performance in the free-field environment that one encounters (approximately) in the deep ocean; however, improvements in tracking performance in shallow water are not assured since both targets and clutter will be tracked continuously and HDC may increase false tracks to an unacceptably high level – essentially continuously tracking the clutter. Theoretical predictions of performance are challenging since the reverberation background for shallow water HDC has not been accurately modeled. To compare performance of HDC with conventional PAS in the littorals, a set of experiments were conducted as part of the Target and Reverberation Experiment (TREX) in spring 2013. This was the first scientifically controlled experiment conducted in the littorals to compare the environmental effects on these two approaches to active sonar. In this project the data from TREX will be analyzed to provide a quantitative comparison of the impact of the environment on the two techniques.