Piezoelectric Ring and Spherical Transducers Designed to Vibrate in a Dipole Mode

Abstract

Free-flooding piezoelectric ring transducers have good efficiencies, are capable of radiating high acoustic power, are of simple design, and have the mechanical strength required for deep underwater submergence operation. However, the omnidirectional acoustic radiation in the plane of a ring transducer is undesirable for applications where directional beams are required. Directional acoustic beams may be obtained from nondirectional transducers by the use of reflectors that are bulky, costly, and difficult to maintain for large low-frequency arrays or by using volume arrays in which the transducer elements are spaced and phased in such a manner that acoustic radiation from all transducers adds in the direction along the acoustic axis of the array and cancels in the opposite direction. Since the technique used to get directionality from biplanar or volume arrays controls acoustic radiation only along the 0° and 180° but not the 90° and 270° directions associated with beam pattern charts, the system works best when transducers with dipole (figure-eight type) beam patterns are used. The design of a dipole ring and spherical transducer will be discussed and measurement data presented.