A Multi-Directional Single-Proof-Mass Accelerometer Contact Microphone (Accelophone) with 10Khz Open-Loop Bandwidth

Abstract

This paper reports on the implementation and characterization of a hermetically-sealed single-proof-mass multi-directional accelerometer contact microphone exhibiting wide operational bandwidth (>10kHz) and low noise (Brownian noise <10µg/√Hz). The device employs a decoupling frame to enable translational motion in all three directions and utilizes dedicated differential sense electrodes along three axes to minimize cross-axis sensitivity. All the tethers supporting the proof-mass are formed in the single crystal silicon device layer having 40µm thickness, thereby increasing robustness and manufacturability of the sensor. The 3mmx3mm vibration sensor exhibits an open-loop flat gain response from DC to 10kHz, making it suitable for use in emerging health monitoring applications that require high-precision high-bandwidth vibration sensors.