Study of structural noise owing to nonlinear behavior of capacitive microphones

Abstract

This paper deals with the study of structural noise in a capacitive MEMS microphone, which consists of a fully clamped circular micro-plate. The micro-plate is subjected to a bias DC voltage and sound pressure waves. Due to the nonlinearity and displacement dependency of the electrostatic force, the amplitude of the applicable bias DC voltage has some limitations and also this nonlinearity causes the generation of super or sub-harmonic responses and consequently the initiation of the structural noise in capacitive microphones. In order to determine the amplitude of the generated structural noise in these microphones, the first order multiple scales method is used and asymptotic analytical solution of the dynamic response is presented. The effects of the bias DC voltage value on the fundamental frequency, sensitivity and consequently on the amplitude of the structural noise of the microphone are studied. In addition the effects of the sound pressure frequency and amplitude on the value of structural noise are investigated.