The design of efficient broad-band piezoelectric transducers

A design method for acoustic thin disk transducers with high efficiency, broad bandwidth, and good impulse response is presented. This method is based on the use of quarter-wave matching layers between the piezoelectric material and the acoustic load. As is made evident using the transmission line model of Krimholtz, Leedom, and Matthaei, the finite thickness of the piezoelectric material must be taken into account in the matching layer design. Criteria for optimum broad-band transducer designs with a given piezoelectric material are developed which show the importance of a high electromechanical coupling coefficient. A method for obtaining Gaussian shaped passbands, necessary for optimum impulse response, is also shown. Several transducers have been built to illustrate this design approach with excellent agreement between theory and experiment. One such transducer has 3.2 dB round trip insertion loss and one octave bandwidth.