Three-Port Piezoelectric Microphone with Stiffness Modification Based on DC Bias

MEMS microphones play a crucial role in the field of acoustic sensing. One of the longstanding challenges is improving sensitivity while preserving acceptable linearity, particularly under high sound pressure level (SPL) conditions. This paper introduces a three-port piezoelectric microphone that incorporates DC bias-stiffness modification to improve microphone performance for high acoustic overload point (AOP) applications. Utilizing PZT polarization characteristics, the characteristic frequency of the microphone can be modulated from 43.87 kHz to 46.40 kHz by applying a 0-9 V DC bias to the stiffness modulation electrodes, theoretically corresponding to a 12% change in stiffness. Moreover, the correlation coefficient of output voltage under different SPL was successfully improved from 0.9754 to 0.9967, which indicates an enhanced linearity, while the variation in sensitivity remained less than 3 dB. Furthermore, the stiffness modification through DC bias can be executed dynamically after the device fabrication, which has the potential to enable more applications, particularly in high SPL scenarios.