CMUT with mechanically coupled plate actuators for low frequencies

In this paper we present a structural analytical model for a capacitive micromachined ultrasonic transducer (CMUT), based on a sacricial release fabrication process and comprised of electro-mechanical plate actuators transferring their motion to a coupling roof structure on top. The structure features a larger average displacement compared to conventional designs at lower
operational frequencies. Low operational frequencies in the range of 40 kHz to 1MHz are benecial for airborne applications due to their frequency-dependent strong wave attenuation in air, limiting the signal-to-noise ratio. The eigenfrequency in dependence of the roof mass is calculated analytically and lumped elements, which can be used in equivalent circuits, are extracted. In addition, nite element analyses utilizing a shell-beam model are conducted. Experimental results, based on digital holographic microscopy, reveal the usability of the deduced model within an uncertainty of 8 %. The developed dimensionless form of the analytical model can be used for future design purposes.