Experimental Validation of an Improved PMUT Model Based on Elastic Supports

Analytical models of piezoelectric micromachined ultrasonic transducers (PMUTs) often assume clamped edges, but this simplification causes deviations with experiments, as actual PMUTs are supported by elastic anchors and surrounded by neighboring elements in an array. This work experimentally investigates the effect of compliant support in PMUTs and proposes a model with improved accuracy in predicting the electroacoustic performance. The proposed model is based on a plate model with elastic torsional and rotational edge supports, with spring stiffness parameters determined by minimizing the deviations between the measured and modeled displacement profiles while restricting the modeled resonance frequency to within a small range of the measured value. The model was tested on an element in a 2D array of cavity SOI-based PZT PMUTs operating in air. The vibration measurements were performed using a digital holographic microscope. The proposed model based on a plate with elastic supports improves prediction accuracy of displacement by 94%, compared to the clamped plate model. Moreover, relative to the measurements, the deviation of the predicted resonance frequency using the proposed model was 4%, while this was 13% for the clamped plate model.