摘要
This study presents the design and realization of a piezoelectric MEMS microspeaker for high-frequency enhancement. Based on piezoelectric thin film actuation, designs of cantilever diaphragms are conducted by modal analysis. Under a die size of 2.5 mm (w) × 5 mm (l) × 0.4 mm (t), the diaphragms are designed to include mid-range and tweeter units with regard to the balance of radiation area and sound pressure contribution. Furthermore, the out-of-phase driving of the proposed device can ensure that the superposition of the sound pressure level (SPL) is within the target frequency range (8-13 kHz) while reducing the SPL outside the target range. In pressure-field measurements, the proposed multi-shape cantilever array can produce high average SPL (91.6 dB) in the target frequency range from 8 kHz to 13 kHz and has a low total harmonic distortion (THD) of <1.4% under a 0.707 V <sub>rms</sub> input signal. The performance can be further improved by biasing the input signal. With a 9 V bias, the average SPL of the proposed microspeaker in the target frequency range is enhanced to 99.4 dB, and the average THD is reduced to <0.7%. In addition, the THD from 7.7 kHz to 18 kHz is below 2.5%. This study shows the great potential of piezoelectric MEMS microspeakers for in-ear applications.