A digital feedback damping scheme for a micromachined directional microphone

Robust Control Design for Resonance Damping of a Directional Microphone

“…In terms of resonance damping, this paper extends previous work presented by Wu et al (Wu et al [2004]) where feedback control is applied to actively damp the resonant frequency of a micromachined directional microphone of the parallel plate configuration, and the nonlinearity in electrostatic force is overcome by using a digital implementation called a sigma-delta (Σ∆) control-loop by the authors borrowing the sigma-delta modulator technology (Azis et al [1996]). However, uncertainties in design model were not considered in the earlier work.…”

“…Because of the configuration of the two isolated backplates playing the role of voltage-to-force transducers, the feedback force energizes the two backplates one at a time, through a couple of nonlinear switches. The two feedback signals pull on the corresponding side of the diaphragm to affect the damping (Wu et al [2004]). Additionally, the capacitance between the parallel plates and the diaphragm is a function of the linear displacement x.…”

Analysis of active damping of a silicon microphone using a linear controller

“…Feedback control can also help expand the bandwidth of the microphone. An analysis of an active damping scheme indicates it can be effective in our design of an older generation of directional microphones incorporating parallel plate capacitive actuation, where digital control using sigma-delta modulation principle was utilized [3]. The effectiveness of active damping has also been shown in highly sensitive gravitational detectors [4], [5].…”