Abstract
This study presents the piezoelectric microspeaker that incorporates a novel ring actuator into the existing spring-diaphragm design. In additional to the spring-actuator, the ring-actuator provides additional actuation force to the microspeaker, improving the diaphragm displacement. Features and merits of the proposed design include: (1) shorter spring-actuators: increase structural stiffness and induce piston motion of the diaphragm to ensure the linear structure movement, (2) dual-electrodes on the springs: provide out-of-phase driving signals to enhance actuation based on stress distribution, (3) ring-actuator: provide additional actuation force and displacement to the diaphragm to further enhance SPL (Sound-Pressure-Level). Measurements at 0.707 V <sub>rms</sub> (9 V <sub>DC</sub> ) in a pressure-field ear simulator show that the proposed design achieves more than two-fold bandwidth enhancement (> 70 dB, 2.6 kHz ~ 20 kHz) compared to the reference design. Furthermore, proposed design also demonstrates low THD (Total-Harmonic-Distortion) (< 10%, 1 kHz ~ 20 kHz), meeting the criteria for a high-fidelity, wide-bandwidth microspeaker.