Design of a wideband multimode tonpilz transducer with a nonuniform piezoelectric layer stack

Abstract

It has been well-known that a multimode transducer could provide a wider frequency bandwidth than a single mode one, and conventionally a multimode transducer can be achieved by designing the geometry of its head mass, increasing the head mass radius and reducing the head mass thickness. However, a very large head mass can cause some drawbacks to transducer performance when used in an array, i.e., low source level and big crosstalk with neighboring transducer elements. In this work, a new and very simple design method has been developed to widen the bandwidth of a Tonpilz transducer, which is replacing the uniform PZT layer stack by a nonuniform one. A piezoelectric stack composed of nonuniform PZT layers can generate higher mechanical energy than that composed of uniform layers for the same input electrical energy, which means a higher coupling coefficient thus a wider bandwidth. The effects of the nonuniformity of PZT layer thicknesses on a multimode Tonpilz transducer performance were investigated through finite element analyses. Then, the functional forms of the performance were derived in relation to the nonuniform PZT thicknesses and were inserted into a genetic algorithm to achieve the widest possible bandwidth of the Tonpilz transducer.