Data-Over-Sound With PMUTs

Data-over-sound is an emerging technology for digital communication which uses frequencies at the upper bounds of human hearing, usually between 15 kHz to 25 kHz. We report a successful development of Piezoelectric Micromachined Ultrasound Transducers (PMUTs) for low-power data-over-sound applications. Piezoelectric thin films used in PMUTs can have high residual tensile stresses ranging from 300 MPa to 1.5 GPa. These stresses have the effect of increasing the resonant frequencies of the transducers, making it a challenge to fabricate low frequency devices. Using the optimum dimensions by estimating the net residual stress in the fabricated diaphragms, transducers suitable for a frequency range of 17 kHz to 21 kHz were fabricated, capable of generating as much as 83 dB of sound pressure level at a distance of 5 cm in continuous operation.