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

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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This thesis presents a detailed SIMULINK model for a conventional capacitive Σ-Δ accelerometer system consisting of a MEMS accelerometer, closed-loop readout electronics, and signal processing units (e.g. decimation filters). By using this model, it is possible to estimate the performance of the full accelerometer system including individual noise components, operation range, open loop sensitivity, scale factor, etc. The developed model has been verified through test results using a capacitive MEMS accelero...
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This thesis presents the design, fabrication and characterization of a high performance, integrated, resonant MEMS temperature sensor, and temperature compensation of a capacitive MEMS accelerometer. Two different double-ended-tuning-fork (DETF) type resonator designs are developed and characterized for temperature sensing. The strain-amplifying beam structure is added to the DETF resonators in order to enhance thermal strain induced on the DETF tines due to the different thermal expansion coefficients of t...
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Demirhan, Gülşah; Akın, Tayfun; Department of Electrical and Electronics Engineering (2016)
The idea of the proposed study is using the resonator structure as a temperature sensor together with controller circuitry. That is to say, the study consists of two branches; one is PI controller output which would be used as a temperature sensor and the other is preamplifier output which would be used as carrier generator to the accelerometer readout circuitry. The proposed resonator is analyzed in detail in terms of dynamics, simulation models and theoretical investigations. The implemented resonator is ...
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This thesis presents the quasi-static acceleration compensation methods for a fully decoupled MEMS gyroscope. These methods are based on the utilization of the amplitude difference information between the residual quadrature signals on the differential sense mode electrodes to sense the static acceleration acting on the sense mode of the gyroscope. There are three different quasi-static acceleration compensation methods presented in this thesis. In the first method, the static acceleration is measured by co...
A Readout circuit for resonant MEMS temperature sensors
Asadi, Hamed; Akın, Tayfun; Azgın, Kıvanç; Department of Electrical and Electronics Engineering (2016)
High precision is the dominant advantage that resonant sensors have over other types of analog sensors (sensors with a subsequent analog-to-digital converter). The resolution of these precise sensors is determined by both frequency resolution and sensitivity of the sensor. The sensitivity is highly related to the sensitivity of the MEMS resonator. However, the frequency resolution is dominantly defined by the closed-loop circuitry if noise contribution of the resonator is assumed to be smaller than that of ...
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.