A well known architecture for A/D-conversion is the Delta/Sigma-modulation. Being applied to microelectromechanical systems (MEMS) it fits perfectly to systems with capacitive transduction, electrostatic force feedback and integrated switched capacitor circuitry. In this work, an improved resolution of micromechanical inertial sensors is achieved, by using the feedback loop, which is inherent to this system architecture, to additionally control the position of the seismic mass. For the system design an analytical model of the Delta/Sigma-modulator is set up. The model describes the transduction, stability and conversion properties for one- and multidimensional position controls. The noise of the sense amplifier is identified as a significant signal source in a micromechanical Delta/Sigma-modulator and is included in the model. A new, energy based macromodeling method for flexible, squeeze film damped multielectrode structures is used to characterize the micromechanical components. The resulting models are particularly suitable for an efficient system simulation in a network simulator. They feature non-linearities and coupling mechanisms of the structure and can be used in the analytical model. The improved resolution of inertial sensors using force-feedback Delta/Sigma-modulators is illustrated by examples. Experimental results of an acceleration sensor with enhanced sensitivity verify the analytical model and demonstrate an increase in resolution by 12dB, reducing the input related noise floor to 1.6mgearth,rms/√Hz.
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A well known architecture for A/D-conversion is the Delta/Sigma-modulation. Being applied to microelectromechanical systems (MEMS) it fits perfectly to systems with capacitive transduction, electrostatic force feedback and integrated switched capacitor circuitry. In this work, an improved resolution of micromechanical inertial sensors is achieved, by using the feedback loop, which is inherent to this system architecture, to additionally control the position of the seismic mass. For the system de...
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