Piezoelectric micromachined ultrasonic transducers (PMUTs) are commonly employed in applications such as medical imaging and gesture recognition. One important performance metric for PMUTs is the quality factor. However, once fabricated, PMUTs have fixed parameters, making them non-tunable for adaptation to various scenarios. This paper presents a technique for using feedback circuits to regulate the bandwidth and quality factor of PMUTs, thereby broadening the potential applications for fabricated PMUTs. First, the electrical characterization of a ScAlN-based PMUT was implemented to extract the parameters in the Butterworth-Van Dyke (BVD) model, which was used in the circuit
design simulations.
Second, the circuit was designed to control the quality factor and bandwidth, simply by adjusting variable resistors in the feedback loop. The characterization results of PCB validated the function of the design. The difference with simulation results was analyzed. Finally, the ultimate performance of the circuit was characterized by a wire-bonded PMUT. The results show that the proposed circuit design effectively manages the Q-factor from 279 to 576 in the quality factor increasing circuit, and 279 to 180 in the quality factor decreasing circuit.