A nonlinear large signal equivalent circuit model for a square CMUT cell

Abstract

Using analytical calculations, a precise large signal equivalent circuit model of square CMUT dynamics was developed. The model predicts many intrinsic properties of a square CMUT cell including resonance frequency, phase and magnitude of the membrane displacement, membrane velocity, electrical conductance, collapse voltage, etc. ANSYS 3D finite element analysis (FEA) was used to validate the equivalent circuit model predictions by performing static, pre-stressed harmonic and nonlinear transient analysis. The model was designed and implemented in a circuit simulator and then compared with finite element methods (FEM) and experimental results. The results were compared with circular CMUT cells when the half-side-length of the square CMUT is assumed to be equal to the radii of the circular CMUT cell. A silicon-nitride standard sacrificial release process was used to fabricate the square CMUT cells. The experimental results obtained by a laser vibrometer were compared with circuit simulations and the results showed excellent agreements.