摘要
This study presents a 65-kHz piezoelectric micromachined ultrasonic transducer (PMUT) with a double-side patterned four-port electrode configuration for investigating airborne transmission performance and burst-driven nonlinear behavior. The fabricated aluminum nitride (AlN)-based PMUT employs segmented center and side electrodes on both top and bottom conductive layers, enabling region-selective and antiphase excitation on the same membrane. The device was fabricated using an in-house five-mask lithography process and experimentally characterized for its electrical, mechanical, and acoustic performance. Compared with conventional driving configurations implemented on the same device platform, the double-side patterned four-port excitation rendered higher measured acoustic output, reaching 98.27 dB (1.64 Pa) at 30 cm under ten-cycle burst excitation, and increasing to 100.79 dB (2.19 Pa) and 100.9 dB (2.36 Pa) through 20 and 40 cycles, respectively. More importantly, the measurements show that high drive level together with a finite number of excitation cycles induces pronounced Duffing-type hardening, accompanied by burst-dependent frequency shift, envelope distortion, and pressure gain saturation at longer burst lengths. The peak-response frequency shifts up to about 8%, indicating a practically useful tunable operating window. Overall, the double-side patterned four-port AlN PMUT serves not only as a transmitter with enhanced measured airborne output under the reported conditions but also as a useful test vehicle for revealing how drive amplitude and burst length govern nonlinear transient behavior and practical frequency tuning in airborne ultrasonic transduction and range-finding applications.