Off-Resonance Dynamics Behavior of Piezoelectric Micromachined Ultrasonic Transducer

Abstract

Piezoelectric micro-machined ultrasonic transducers have gained popularity in VR, cell phone and other electronic devices for its low power consumption, high stability and CMOS compatibility. Off-resonance behavior of ultrasonic transducer commonly exists in ultrasonic Doppler measurement. In this paper, we studied the off-resonance behavior of the ultrasonic transducer from both theory and experiment, demonstrating that the test result matches well with the dynamic theory. The solution of dynamic equation is deduced, which is capable of describing every stage of pMUT behavior. An envelope method is proposed to identify the resonance of the pMUT and detect the frequency shift of driving signal or ultrasound signal. The initial off-resonance response behavior in linear excitation range can be used for device characterization and pulse-Doppler velocity measurement. In addition, such an envelope curve measurement can significantly reduce the sampling rate and cost down the hardware, especially in a high frequency application.