Design and Optimization of a BAW Microphone Sensor

A wind tunnel experiment is an important way and effective method to research the generation mechanism of aerodynamic noise and verify aerodynamic noise reduction technology. Acoustic measurement is an important part of wind tunnel experiments, and the microphone is the core device in an aerodynamic acoustic measurement system. Aiming at the problem of low sound pressure (several Pa) and the small measuring surface of an experimental model in a wind tunnel experiment, a microphone sensor head with high sensitivity and small volume, based on film bulk acoustic resonator (FBAR), is presented and optimized in this work. The FBARs used as a transducer are located at the edge of a diaphragm for sound pressure level detection. A multi-scale and multi-physical field coupling analysis model of the microphone is established. To improve the performance of the microphone, the structural design parameters of the FBAR and the diaphragm are optimized by simulation. The research results show that the microphone has a small size, good sensitivity, and linearity. The sensor head size is less than 1 mm × 1 mm, the sensitivity is about 400 Hz/Pa when the sensor worked at the first-order resonance frequency, and the linearity is better than 1%.