Accurately Predicting the Performance of Polymer-Based CMUTs by Coupling Finite-Element and Analytical Models

This paper introduces a hybrid modeling approach to accurately predict the performance of polymer-based Capacitive Micromachined Ultrasonic Transducers (polyCMUTs) by coupling finite element analysis (FEA) with analytical methods. The coupled FEA and analytical (CFA) model integrates characteristics from a single-cell FEA into a multi-cell equivalent circuit. Acoustic cross-coupling between cells is considered using analytical methods, and the acoustic far-field is computed via the Rayleigh integral. We validated the model on rectangular designs with 11x11 cells and varying cell-to-cell pitches. CFA results showed in average less than 7% deviation from full FEA in terms of center frequency, fractional bandwidth, and peak sensitivity, while requiring less than 1% of the computation time. We also observed good agreements with measurements, with a deviation of 17% for the rectangular designs and less than 4% for a larger linear array element (428 cells) we recently produced. This makes the CFA model a powerful tool for fast design exploration and optimization of CMUTs.