Passive underwater acoustic tags with curved symmetry for navigation and information encoding

Passive acoustic beacons built of horizontally stratified materials have been designed in previous literature to assist in the navigation of autonomous underwater vehicles (UAV) equipped with SOund Navigation and Ranging (SONAR) instrumentation. These beacons reflect a characteristic acoustic signature which can be detected by the AUV as acoustic backscattering upon tag insonification. Currently, only backscattering from acoustic waves normally incident on a beacon can be detected by the AUV due to the beaconu0027s planar geometry. To address this issue, this paper proposes the design of passive acoustic beacons with curved symmetry, whose acoustic backscattering is the same irrespective of the angle of source incidence. Simulation and experimental results are discussed for beacons made of concentric spherical shells as a proof of concept.