Evolution of Phononic Frequency Combs in Curved Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) under Single-tone Actuation

In this work, we present the phenomenon of phononic frequency combs in curved piezoelectric microma-chined ultrasonic transducers (PMUTs) under single-tone actuation. The curved PMUT is fabricated using in-house fabrication facilities. The initial curvature of the PMUT is characterized using 3D topography, while mechanical amplitude-frequency response and nonlinear behavior are evaluated using a Laser Doppler Vibrometer. A single-tone drive method is employed to observe frequency combs across various input frequencies and voltages. As a result, we successfully generate and demonstrate frequency combs in the FFT response at a single-tone input of 205.8 kHz with 500 mV. Furthermore, we observe various comb spacings in the range of actuation frequencies from 206 kHz to 206.7 kHz at 700 mV.