Dynamics of piezoelectric micro-machined ultrasonic transducers for contact and non-contact resonant sensors

The dynamics of piezoelectric micromachined ultrasonic transducers (pMUTs) are studied, and an envelope method is proposed for measuring the frequency shift when they operate in pulse–echo mode. To understand pMUTs comprehensively, a theoretical model is established and the dynamic equation is solved, and the experimental results match well with the theoretical ones. A pMUT is measured for each stage of its off-resonance dynamic response with pulse excitation. Through the proposed method, the pMUT can work as either (i) a contact resonant sensor to measure the resonance frequency shift induced by an external mass or pressure or (ii) a noncontact ultrasonic transceiver to detect velocity by the Doppler effect. Tests with both electrical and acoustic signal excitation validate the ability to detect a frequency shift through a predictable transient response. In addition, such an envelope-curve measurement can significantly reduce the sampling rate and lower the hardware cost, especially for high-frequency applications.The dynamics of piezoelectric micromachined ultrasonic transducers (pMUTs) are studied, and an envelope method is proposed for measuring the frequency shift when they operate in pulse–echo mode. To understand pMUTs comprehensively, a theoretical model is established and the dynamic equation is solved, and the experimental results match well with the theoretical ones. A pMUT is measured for each stage of its off-resonance dynamic response with pulse excitation. Through the proposed method, the pMUT can work as either (i) a contact resonant sensor to measure the resonance frequency shift induced by an external mass or pressure or (ii) a noncontact ultrasonic transceiver to detect velocity by the Doppler effect. Tests with both electrical and acoustic signal excitation validate the ability to detect a frequency shift through a predictable transient response. In addition, such an envelope-curve measurement can significantly reduce the sampling rate and lower the hardware cost, especially for high-frequency ap...