An accurate model for capacitive micromachined ultrasonic transducers

Abstract

Modeling of capacitive micromachined ultrasonic transducers (cMUTs) is based on a two-port network with an electrical and a mechanical side. To obtain a distributed model, a solution of the differential equation of motion of the diaphragm for each element of the transducer has to be found. Previous works omit the mechanical load of the cavity behind the diaphragm, i.e., the effect of the gas inside. In this paper, we propose a distributed model for cMUTs that takes this effect into account. A closed-form solution of the mechanical impedance of the membranes has been obtained, including the effect of the restoring forces because of the stiffness of the membrane and because of the compression of the air in the cavity. Simulation results based on the presented model are compared with the experimental data for two types of cMUTs reported in the recent literature. It is demonstrated that the compression of the air has a significant effect on the fundamental frequency of the air transducer, with a deviation of about 22% from the prediction of a model that does not consider the interaction between the vibrating diaphragm and the air cushion

Theoretical model and optimal design of silicon micromachined ultrasonic imaging transducers

“…[2], the fundamental frequency calculated is only 3.66 MHz by the formula 01 2.405 s T a ω ρ = [17] . Note that Caronti et al [18] treated the diaphragm as a stretched membrane enhanced by the compressibility of the air, gave simulation results, and claimed that it is an accurate model. However, the model did not take into account the bending stiffness of the membrane, and also omitted the effects of the metal electrode.…”

A theoretical model of a new electrostatic transducer incorporating fluidic amplification

“…We start by adapting the three-dimensional CMUT model proposed by Caronti et al [3] to include the effects of the air load on both sides of the membrane. We reduce the spatial dimensionality to unity by assuming that the membrane acts in a piston like manner.…”

Finite-Element Electroacoustic Analysis and Taguchi Design of Piezoelectric Buzzers Based on the Vibration Absorber Model

“…Aronov [8,9] applied energy methods to analyze the piezoelectric transducers and established a model for simulation. Similar methodology was also applied to other piezoelectric transducers, e.g., panel speakers [10] and ultrasonic transducers [11,12] etc. Caronti et al [12] modeled a capacitive micromachined ultrasonic transducer by a two-port network.…”

“…Similar methodology was also applied to other piezoelectric transducers, e.g., panel speakers [10] and ultrasonic transducers [11,12] etc. Caronti et al [12] modeled a capacitive micromachined ultrasonic transducer by a two-port network. Gallas et al [13] used lumped-element models to examine the frequency responses of a piezoelectric-driven synthetic jet actuator.…”

“…The finite element analysis is carried out for only piezoelectric diaphragm (PZT and metal plate). The FEM model is then converted to a two-port [12] model that can readily fuse into electro-mechano-acoustical (EMA) [15,16] analogous circuit of the system. An addedmass method similar to that used to electrodynamic loudspeakers is then used to determine lumped parameters [15,16].…”