AUV navigation requires accurate positioning information from the surrounding environment. Currently, several underwater navigation and surveying paradigms employ active transponders that assist in triangulation. These systems are expensive, require maintenance, and additional power sources. This paper presents a novel system that may be implemented to guide AUVs equipped with high frequency SONAR, using passive acoustic tags that are cost effective, and simple to deploy. The acoustic tags are constructed by layering multiple sheets of different acoustically reflective materials. When a deployed tag is ensonified by an encoded signal sent from a collocated source/receiver pair, the backscattered waveform by the tag yields a time-domain signature unique to the properties of the materials and geometry of the tag. The signature can be used to locate and identify any given tag within a known library of various tag designs. Numerical simulations and experimental results will demonstrate the feasibility of the proposed passive acoustic tag approach. The developed acoustic tags may find application in AUV navigation and docking exercises, swarm AUV vessel identification, AUV route planning, tagging undersea ecosystem boundaries, etc.
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