Analysis of frequency response behaviour of capacitive micromachined ultrasonic transducers

In Capacitive Micromachined Ultrasonic Transducers (CMUTs), the metalized membrane is in forced vibration with the applied ac bias. The resonance frequency of the ultrasonic waves generated by the vibrations of the membrane is evaluated by modeling the device with mathematical analysis, approximating the membrane shape to be circular. The device is simulated by finite element method (FEM) and the resonance frequency is evaluated from Fast Fourier Transform (FFT) of the displacement profile of the biased membrane in the time domain. It is found that CMUT is a multiple resonance device. The amplitude decreases as we operate at the subsequent resonances rather than the fundamental resonance. The expression of modeled fundamental resonance does not resemble with published literatures but its value matches with the published experimental results. The resonance frequency is solely dependent on the membrane material and structural properties. Its value increases with a decrease in the radius of the membranes and is higher for denser membranes with lower residual stress. Moreover, it is found that to operate the device in the range of megahertz for medical imaging purposes, the structural dimension needs to be in the order of micrometers. Copyright © 2015 American Scientific Publishers.