Modal analysis based equivalent circuit model and its verification for a single cMUT cell

Abstract

This paper presents the lumped equivalent circuit model and its verification of both transmission and reception properties of a single cell capacitive micromachined ultrasonic transducer (cMUT), which is operating in a non-collapse small signal region. The derivation of this equivalent circuit model is based on the modal analysis techniques, harmonic modes are included by using the mode superposition method; and thus a wide frequency range response of the cMUT cell can be simulated by our equivalent circuit model. The importance of the cross modal coupling between different eigenmodes of a cMUT cell is discussed by us for the first time. In this paper the development of this model is only illustrated by a single circular cMUT cell under a uniform excitation. Extension of this model and corresponding results under a more generalized excitation will be presented in our upcoming publication (Mao et al 2016 Proc. IEEE Int. Ultrasonics Symp.). This model is verified by both finite element method (FEM) simulation and experimental characterizations. Results predicted by our model are in a good agreement with the FEM simulation results, and this works for a single cMUT cell operated in either transmission or reception. Results obtained from the model also rather match the experimental results of the cMUT cell. This equivalent circuit model provides an easy and precise way to rapidly predict the behaviors of cMUT cells.