A study of the design and the radiation patterns of rectangular bimorph acoustic transducers with thin piezoelectric ceramic plates

Abstract

In this article, the design of asymmetric bimorph piezoelectric ceramic transducer with loose and fixed edges and with parallel electric excitation is studied. Rectangular piezoelectric ceramic transducers in flexural vibration with straight and parallel nodal lines of vibration are studied. The transducer’s radiation in a plane perpendicular to the surface of the transducer and parallel to the nodal lines of vibrations is examined. By using the classic theory, the radiation patterns of such transducers are evaluated. The radiation pattern of the transducer is evaluated in a plane, perpendicular to the direction of flexural vibration of the nodal lines. In another perpendicular plane the radiation pattern of the transducer is calculated the same as for an oscillating piston. Diagrams to calculate these radiation patterns are supplied. It is mentioned that for effective operation of such transducers vibrations of the piezoelectric ceramic plate arrays with the vibrations of elastic plates, on which the arrays are mounted, must be matched. It is noted, that when calculating the radiation patterns of simple bimorph rectangular transducers, the expressions of the transducer’s flexural vibration mode must be evaluated. When calculating radiation patterns of multi-component rectangular transducers, the distribution of vibrations on the transducer’s surface can be evaluated as harmonic. It is noted, that the angle between a normal to a flat transducer’s surface and direction of radiation depends on the acoustic wavelength ratio in the transducer and the working environment. The value of this angle can change by small amounts, dependant on the operating frequency. A design of a unidirectional acoustic antenna, consisting of an array of four such transducers is presented.