Abstract
This study presents the piezoelectric MEMS microspeaker with an area under 5.3 mm for high-frequency applications. The multiple tweeter units together with the driving circuits are designed to extend the bandwidth from 5 kHz to 13 kHz. Features and merits of the design to modulate resonant frequencies of the tweeters to extend the bandwidth are: (1) curve slit: to modulate the cantilever resonant frequency under the same anchor and diaphragm area, (2) central joint: to connect part of the cantilevers to form different tweeter units, (3) driving circuits: to implement the gain and phase modulation driving signals to extend the SPL (Sound-Pressure-Level) in specific frequency ranges. Measurements under 1 Vpp with 8 Vdc driving voltage in the pressure field, the proposed design with phase modulation driving achieves over 80 dB from 5 kHz to 13 kHz. Moreover, THD (Total-Harmonic-Distortion) is below 3% at the same time.