Electromechanical Equivalent Circuit Model for Axisymmetric PMUTs With Elastic Boundary Conditions

Here we present an electromechanical lumped equivalent circuit model for the purpose of deriving the electrical input impedance and response of air-coupled axisymmetric polymer-based piezoelectric micromachined ultrasonic transducers (pMUT). In particular, this study presents the derivation and validation of polyvinylidene fluoride-co-trifluoroethylene P(VDF-TrFE) unimorph pMUT equivalent circuit models operating in the fundamental axisymmetric mode. Derivation of the equivalent circuit model is performed via the application of the Rayleigh-Ritz energy method towards determining effective pMUT radii due to an elastic boundary condition. The results of the model are shown to be in good agreement with finite element (FEM) simulations and experimental measurements of discrete pMUTs in air. In particular, the model is able to accurately predict the effective expansion in the pMUT radius due to the elastic boundary. The electromechanical model may also be used as a tool to characterize and/or evaluate the behavior of pMUT designs for ultrasound transducer applications. [2021-0156]