Broadband Piezoelectric Micromachined Ultrasonic Transducer With a Resonant Cavity

This article presents a broadband piezoelectric micromachined ultrasonic transducer (PMUT) surrounded by a resonant cavity called C-PMUT. The C-PMUT shows two resonance peaks derived from the resonances of the active PMUT cell and the passive resonant cavity. Both of the two resonances vibrate at the first-order resonant mode. An equivalent circuit model is established considering the vibration of the resonant cavity and the crosstalk between the PMUT cell and the resonant cavity. Finite element analysis (FEA) has been used to verify the theoretical model. Bandwidth optimization has been operated and the -6 dB bandwidth is extended to more than 100% in liquid. Furthermore, the theoretical model of the C-PMUT array is established based on the C-PMUT cell. The FEA models of the C-PMUT arrays are proposed, and the -6 dB bandwidth of a 4 x 4 C-PMUT array is increased to 2x compared to the traditional array. Therefore, the C-PMUT provides a novel broadband strategy for future real-time ultrasound imaging.