Abstract
A dielectric loss of a piezoelectric transducer decreases the mechanical Q under the electric terminal condition in short-circuit, and makes it small in comparison to that under the open-circuit condition. Even if the loss angle δ is small, this effect cannot be neglected in transducers with high electromechanical coupling. However, the conventional equivalent circuit of piezoelectric transducers fails to represent this kind of effect due to the dielectric loss by only adding a shunt conductance to the clamped capacitance Cd. This inconvenience comes from the fact that all the elements in the conventional circuit, including Cd, are required to take complex values when δ=0. In this paper, the equivalent circuit applicable to the case of δ=0 is theoretically derived. The improved circuit consists of only real constant elements, independent of the frequency. Validity of the obtained circuit is demonstrated by the experiments on radial mode transducers.
