Wideband Air-coupled Piezoelectric MEMS Ultrasonic Transceiver

Piezoelectric micromechanical ultrasonic transducers (pMUTs) operating in air have received great attention for airborne applications. Indeed, air-coupled pMUTs have lower resonant frequencies and unfortunately suffer from low fractional bandwidth. This study proposes a novel geometry for pMUT transceivers which can be fabricated using standard bulk micromachining processes. The proposed design consists of four standalone triangle-shaped flags, each positioned adjacent to the other with a mirrored orientation and an air gap size of 2 μm, forming an overall square configuration. The design is fabricated using a commercially available PiezoMUMPs process. The performance of the pMUT in both receiving and transmitting of ultrasonic waves is evaluated. Experimental results show a resonant frequency of 200 kHz and a fractional bandwidth of 30%.