Two-Way Piezoelectric MEMS Microspeaker with Novel Structure and Electrode Design for Bandwidth Enhancement
Yu-Tzu Lin, Sung-Cheng Lo, Weileun Fang
Abstract
This study presents a piezoelectric MEMS tweeter with novel structure and electrodes designs (Fig. 1) for two-way excitation to enlarge its bandwidth, which can meet the requirement of in-ear applications. The proposed design has two merits: (1) Dual-ring spring design: to offer two resonant modes with piston vibrations to contribute sound pressure, (2) Distribution and excitation of driving electrodes design: to achieve the two-way excitation to drive the two required vibration modes. Thus, this proposed design could enlarge the bandwidth at the high frequency range with decent sound pressure level (SPL). Measurements in the standard ear simulator with 2Vpp input voltage demonstrate the presented tweeter has a significant bandwidth improvement of 14 kHz∼30 kHz (for the ±10dB range of SPL (72 dB SPL∼92 dB SPL)).