A broad band dolphin mimetic sonar—inspiration and modification from the nature

Abstract

Broadband techniques are getting popular for underwater sensing methods because of its high spatial resolution and target discrimination abilities. We have been developing a broadband split beam system to locate and identify each species in the ocean. Our system initially learned from dolphins and then modified architecture appropriately. For example, biological sonar sound was effective for the short range sensing to locate individual target, chirp sound provided clear target image for the long range up to 200 m. Multi angle scanning of a target was proved to be essential for the species discrimination in our system. It was just like a finless porpoises rolled their body possibly to enlarge sensing volume and change beam incident angles to a target. Unlike dolphins, the split beam system was not able to change transmitting beam directions. The sound incident angle to a fish was calculated using the body movement vector and the position of a target fish in the beam. Reconstruction of target strength spectrum according to the incident angle provided significant difference of species between jack mackerel and chub mackerel that has not been possible by conventional active sonar systems.