A Versatile 5th order sigma-delta modulation circuit for MEMS capacitive accelerometer characterization /

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2014
Asgarli, Tunjar
With the significant developments in capacitive MEMS inertial sensors, tons of studies in the literature trying to enhance the performance parameters of MEMS capacitive accelerometer systems such as linearity, noise floor and bandwidth further has emerged. However, all the studies are conducted on a certain reference point, which is mainly the properties of the accelerometer sensor that alter a lot in the design of the high performance interface readout circuit. The designed interface circuits usually adopt high dependence on the accelerometer parameters and little variations on the accelerometer sensor due to fabrication impurities may result in the stability collapse of the whole system. Even though the advanced fabrication procedures allow the fabrication of the accelerometers with negligible tolerance and high yield, a precisely characterization extracted circuit is required to qualify the fabricated accelerometer sensor. Such a circuit can propose data readout from capacitive accelerometer of a wide range and high tolerance. This thesis presents the design of a highly coherent accelerometer characterization circuit. The major duty of front end compatibility to variety of sensor with no need to be redesigned is sustained by the use of simple voltage-mode approach. A mixed-signal loop consisting of 2 analog and 3 programmable digital filters is constructed for ΣΔ modulation. PDM voltage output is supplied back to the accelerometer electrodes to end up with closed-loop circuit, increasing the linearity, bandwidth and range of the system in a great sense. The proposed system is simulated in MATLAB Simulink Environment with two different sensors. The system is found out to have 35 μg/√Hz noise floor, nearly quarter of which is caused by the accelerometer.

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Citation Formats
T. Asgarli, “A Versatile 5th order sigma-delta modulation circuit for MEMS capacitive accelerometer characterization /,” M.S. - Master of Science, Middle East Technical University, 2014.