Nonlinear Factors in Single and Double Backplate Capacitive Transducers

Abstract

Capacitive microphones are widely being used in many applications as high-precision instruments for measurement to audio capturing microelectromechanical (MEMS) sensors in common mobile devices, such as portable computers, mobile phones, and hearing aids. The latter have successfully replaced previous technologies such as the electret condenser microphones (ECM) due to their lower sensitivity to temperature variations, smaller footprint, and lower sensitivity to vibration, having a consistent frequency response. However, their widespread use has increased the demand for tighter specifications, especially in loud environments where the total harmonic distortion (THD) and the acoustic overload point (AOP) become significant parameters to the devices' performance. With the aim of providing a more detailed physical understanding of the nonlinear dynamical behavior of double backplate transducers a DC biased parallel plate model of such a device is developed and the effect of the nonlinear factors to the model's nonlinear response are discussed compared to the ones of a single backplate model.