A Large-Signal Nonlinear Equivalent Circuit Model for CMUTs Operating in Collapse and Non-Collapse Modes

Capacitive Micromachined Ultrasonic Transducers (CMUTs) Collapse mode operation offers higher electro-mechanical coupling and transmit pressure compared to non-collapse mode. This paper proposes an Equivalent Circuit Modeling (ECM) approach capable of accurately predicting the large-signal CMUT behavior in both collapse and non-collapse modes. A lumped-parameter nonlinear Equivalent Circuit Model representing the CMUT as a two-port network is implemented in LTSpice. Electro-mechanical and acoustic transduction is described by coupled nonlinear differential equations, i.e., a time-varying capacitance equation relating voltage and current at the electrical port and a force equation balancing elastic, electrostatic, and radiation forces. The nonlinear parameters are computed by Finite Element Modeling (FEM) and implemented in LTSpice using arbitrary behavioral sources and look-up tables.