system and circuit design for a capacitive mems gyroscope - Aaltodoc

Abstract
In this thesis, issues related to the design and implementation of a micro-electro-
mechanical angular velocity sensor are studied. The work focuses on a system based
on a vibratory microgyroscope which operates in the low-pass mode with a moderate
resonance gain and with an open-loop configuration of the secondary (sense) resonator.
Both the primary (drive) and the secondary resonators are assumed to have a high qual-
ity factor. Furthermore, the gyroscope employs electrostatic excitation and capacitive
detection.
The thesis is divided into three parts. The first part provides the background infor-
mation necessary for the other two parts. The basic properties of a vibratory micro-
gyroscope, together with the most fundamental non-idealities, are described, a short
introduction to various manufacturing technologies is given, and a brief review of pub-
lished microgyroscopes and of commercial microgyroscopes is provided.
The second part concentrates on selected aspects of the system-level design of a
micro-electro-mechanical angular velocity sensor. In this part, a detailed analysis is
provided of issues related to different non-idealities in the synchronous demodulation,
the dynamics of the primary resonator excitation, the compensation of the mechanical
quadrature signal, and the zero-rate output. The use of ΣΔ modulation to improve
accuracy in both primary resonator excitation and the compensation of the mechanical
quadrature signal is studied.
The third part concentrates on the design and implementation of the integrated
electronics required by the angular velocity sensor. The focus is primarily on the design
of the sensor readout circuitry, comprising: a continuous-time front-end performing
the capacitance-to-voltage (C/V) conversion, filtering, and signal level normalization;
a bandpass ΣΔ analog-to-digital converter, and the required digital signal processing
(DSP). The other fundamental circuit blocks, which are a phase-locked loop required
for clock generation, a high-voltage digital-to-analog converter for the compensation
of the mechanical quadrature signal, the necessary charge pumps for the generation
of high voltages, an analog phase shifter, and the digital-to-analog converter used to
generate the primary resonator excitation signals, together with other DSP blocks, are