Spurious Mode Free Hexagonal PMUT Array

This paper presents a hexagonal piezoelectric micromachined ultrasonic transducer (PMUT) array that can avoid spurious modes known to occur by mode coupling with adjacent elements. By designing an optimal hexagonal PMUT array with 10 μm spacing resulting in high fill-factor, we were able to experimentally demonstrate well-matched spurious mode free resonances operating around 10 MHz. Furthermore, the effects of the center PMUT in arrays were investigated through various array designs based on finite element method (FEM) simulations and experimental measurements.