Mechanical modeling and sensitivity evaluation of an electrodynamic MEMS microsensor

In this paper, we present the mechanical modeling of a MEMS electrodynamic microphone using finite element analysis. This new model aims to study the mechanical design of a microphone to predict its dynamic range performance. Two coaxial planar inductors, one external and the other is internal, are used in this microphone design. When the external inductor is flown by a current, it will produce a magnetic field within the internal suspended one located onto suspended membrane above a micromachined cavity. In the present study, the membrane is attached around its edges, to avoid opening in the top membrane surface which leads usually to an acoustic short path in low frequencies that can affect the microphone performance. So, both membrane resonant frequency and displacement have been determined according to the used technology in IIT Bombay university- India. The frequency was optimized around 1.6 KHz in the geometric mean of the acoustic band (20 Hz-20 kHz) and the harmonic displacement was around 8μm for the main resonant frequency. Finally, the sensitivity was evaluated by coupling different transducer domains involved in the microsensor principle and by using the lumped element model of the microphone. The ultimate sensitivity was found around 0.1V/Pa, which is considered to be quite good compared to previously published sensitivities.