Anti-intruder port protection “MAC (Magnetic ACoustic) System”: advances in the magnetic component performance

摘要

In the following, we report the advances made in the development of a magneticcomponent for peripheral monitoring of port environments for anti-intrudersystems. The project was initiated by the Office of Research and Development,COMFORDRAG, Italian Navy, in 2004, with the aim of improving the detectionperformance of current acoustic-based anti-intruder systems, in the vicinity ofquays or the seabed or in acoustic-shadow zones behind natural or artificial objects.In the five-year period from 2004 to 2008, the system has been subjected todetection-performance tests in experiments involving divers equipped with air tanksand rebreather kits in real port environments and, at the same time, the associatedsignal processing has been subjected to development, to enhance detectionperformance. In tests involving simulated diver attacks against a vessel mooredalongside a quay in the port of La Spezia, the system has been proved particularlyeffective by detecting 9 divers out of 9. The processing of the magnetic signal hasbeen enhanced by implementing an amplitude threshold, as a means of filtering the passive energy components, termed Passive Energy Cutting (PEC), that is, theelimination of components that comprise no useful information regarding divertransits. The use of PEC boosts the reliability of the system in terms of detectionversus false alarm rate, as evidenced by the comparison of the ROC curves for thesystem with and without PEC.