Analytical characterization and simulation of a 2-D capacitive micromachined ultrasonic transducer array element

In this paper, a capacitive micromachined ultrasonic transducer (CMUT) suitable for 4.5 MHz ultrasound medical imaging is analytically characterized and is found to be in good agreement with the simulated results. The array element is modeled as a circular membrane and the variation of the displacement at the centre of the structure is investigated. This paper reports the result of a timedomain finite element study of this effect. PZFLEX, a commercially available validated finite element package is used for simulation of a two dimensional CMUT cell. It is observed that the influence of the various device parameters on the displacement of the membrane is a very important factor in determining the optimum performance of CMUT. The resonance frequency evaluated from the Fast Fourier Transform (FFT) of the displacement profile of the biased membrane in the time domain, is found to be in good agreement with published experimental results. The mechanical impedance of the membrane is found to match that of air which is about 400 kg m-2 sec-1, at frequencies close to resonance and of negligible value when compared to the impedance of water; hence it relieves us from the search of a suitable matching layer as needed for piezoelectric ultrasonic transducers for air borne and immersion applications. Copyright © 2015 American Scientific Publishers.