Hybrid AIR-Coupled Rangefinder with Sputtered PVD PZT and SC0.2AL0.8N PMUTs for Pulse-Echo Applications

This paper reports a hybrid air-coupled rangefinder using 20% scandium-doped aluminum nitride (ScAlN) piezoelectric micromachined ultrasonic transducer (PMUT) as a receiver and sputtered physical vapor deposition (PVD) lead zirconate titanate (PZT) PMUT as a transmitter to leverage the merits of each material. The presented Sc0.20Al0.80N device boasts high receive sensitivities of 22 mV/Pa without amplification and a -3dB bandwidth of 4.07% while the PVD PZT PMUT transmits an ultrasound wave of 0.16 Pa/V at 40 cm distance with a -3dB bandwidth of 38.3% for optimum transmit-receive performance. By optimizing and matching the resonant frequencies of both the Sc0.20Al0.80N receiver and PZT transmitter, a pitch-catch ranging distance of 3-meters was achieved.