Consistent analytical model for single and dual thickness capacitive Micromachined Ultrasound Transducers (cMUT)

Capacitive Micromachined Ultrasound Transducers (cMUTs) are recognized as key enablers for emerging applications of ultrasound waves in gaseous, liquid and solid-state media, from positioning/ranging to medical treatment, through actuation, levitation, drug delivery, bio-sensing. This paper presents an improved consistent model for cMUTs implementing uniform or bossed membranes in transmit and receive modes. Key in our model are the consistent description of the mechanical modal resonant equivalent circuit and the transduction between electrical, mechanical and acoustic domains as well as the proper description of the acoustic load, not only resistive but also inductive, and thus the accurate representation of the frequency drift introduced by the medium supporting the propagation. In particular, we demonstrate, through comparison with FEM simulations, the accuracy of the model to define the center frequency, 3dB-fractional bandwidth and output pressure levels of cMUTS.