Design, development, and testing of transducers for creating spiral waves for underwater navigation

Abstract

The use of spiral waves for underwater acoustic navigation has received much attention in recent years. A spiral wave is characterized as a diverging wavefront that is omnidirectional by magnitude but with a phase that varies linearly by azimuthal angle. Such a signal may be exploited in underwater acoustic navigation when compared with a reference signal of constant phase with respect to azimuthal angle. This paper summarizes our sine/cosine spiral wave transducer (SC-SWT) design approach, which creates a spiral wave by generating two orthogonal dipoles driven in phase quadrature using the same cylindrical piezoceramic element. Several acoustic navigation beacon designs that also contain the constant-phase reference transducer have now been fabricated, including variants where spiral and referencing sources have the same effective acoustical origin in the horizontal and vertical planes. Experimental results, test tank calibrations, and problems to overcome are presented.