State space modeling of surface mount silicon microphones

Abstract

Most surface mount microelectromechanical system (MEMS) microphone packages are similar in construction, consisting of a printed circuit board with sound inlet, a MEMS die with a through-wafer etch aligned over the sound inlet, and cap which serves to protect the structure and render an enclosed back volume. From a lumped modeling perspective, this system is a network of acoustical and mechanical elements. Network models (i.e., equivalent circuit models) have proven to be the most common modeling technique for simulating important features of these microphones, including frequency response functions and internal noise floors. While these models have many advantages including their ability to be solved efficiently using modern circuit simulation software, they do not lend themselves well to an understanding of system dynamics as a decomposition of the fundamental mechanical modes of the packaged system. We present a state space model for complete MEMS microphone packages and present frequency response simu...