A Novel Coupled Piezoelectric Micromachined Ultrasonic Transducer Based on Piston Mode.

This paper presents a piezoelectric micromachined ultrasonic transducer (pMUT) modified with a piston diaphragm term as PD-pMUT (Piston Diaphragm pMUT). The transmission SPL and the frequency bandwidth of the modified transducer can be remarkably improved by adding a piston diaphragm on the central circular diaphragm. In this work, a lumped model, an acoustic resonance model, and an equivalent circuit model are established to study the multi-resonance mechanism. The second resonance peak is contributed by the interference acoustic wave generated between circular and piston diaphragm. This work demonstrated a simulated far-field average sound pressure level up to 132.2dB in the single modified piston diaphragm structure and a 28.1% -6dB frequency bandwidth by theoretical analysis and parameter optimization. The bandwidth is 3.31 times of the traditional pMUT with Aluminum Nitride (AlN) in air. In addition, the PD-pMUT has a -6dB frequency bandwidth of up to 66% which is 1.4 times of traditional pMUT in liquid-coupled operation. The proposed PD-pMUT provides a new approach for the application of high transmission power and broad bandwidth transducers.