Multi-frequency Harmonic Energy Modification of Piezoelectric Micromachined Ultrasonic Transducer (PMUT) for Advanced Sensing Applications

Piezoelectric micromachined ultrasonic transducer (PMUT) is a strong candidate for next-generation ultrasonic applications due to its small size, high performance, and low power consumption. Typical PMUT sensing utilizes propagation time (Time of Flight, ToF) or attenuation to measure objects indirectly. However, the space for further optimization of the sensing sensitivity and accuracy is usually limited by the single operating frequency. Therefore, integrating multiple operating frequencies in a single PMUT device has been a long-term goal to provide additional sensing information. Meanwhile, high-order harmonics are stereotypically considered harmful for diffusing the excitation energy of the transducer. In consideration of these aspects, this paper proposed a novel technology of multi-frequency harmonic energy modification of PMUT in air, in which the intensity-enhanced second harmonic was used as an additional operating frequency, to offer a high-accuracy optimizing method for application scenarios like miniaturized gas sensors.