A Novel Broadband Piezoelectric Micromachined Ultrasonic Transducer with Resonant Cavity

This paper reports a broadband piezoelectric micromachined ultrasonic transducer (pMUT) with resonant cavity. The resonant cavity between the active diaphragm and substrate is designed to form a second resonance peak near the fundamental resonance peak of pMUT. The electrode coverage is optimized to enhance transmitting performance without any added fabrication complexity. A model for the proposed pMUT is established by combing several equivalent circuits for design and optimization. A systematic design method is proposed to increase the bandwidth of the reported pMUT in liquid-coupled operation. The -6dB fractional bandwidth of the proposed pMUT is 2.7x that of traditional pMUT. The most extensive fractional bandwidth can reach 47.5% in FC-40. This work lays the foundation in the field of high-performance ultrasonic transducer application.