振動式微陀螺儀電路系統之研究

Abstract

本篇論文的研究方向是發展三層多晶矽振動式微陀螺儀的電路系統，其電路系統包含弦波震盪器、位移感測器和ΣΔ A/D轉換器。為了達到積體化的設計目標，所有的電路設計均採用VLSI技術來實現。因此本文將利用適合的電路架構，以獲得穩健的電路系統。 首先，我們採用OTA-C的弦波振盪器，此電路架構在振盪條件與振幅控制上，都是使用轉導放大器的增益作為調整設計，因此OTA-C的設計方式較適合積體電路的實現。其次，位移感測電路我們採取差動式輸出的架構，原因是此電路對於電磁干擾、電源雜訊與熱雜訊有較佳的抵抗力。最後在類比轉數位的訊號上，由於ΣΔ A/D轉換器不像傳統轉換器，必須使用高精度的模組或是增加校正的裝置，來獲得全系統較高的精度。所以在VLSI的技術中，這些架構可以充分得到高解析度類比－數位轉換器的需求，比其他高精確度的類比元件更適合在快速的數位電路中實現。 本文最後將以SIMULINK® 來模擬二階ΣΔ A/D轉換器，其中考慮大多數ΣΔ調變器的非理想現象，藉以觀察量化誤差現象。並列舉單迴路二階ΣΔ調變器電路作為設計目標，其有效解析度為16位元。

The circuitry of Y-axis vibrating microgyroscope is developed in a monolithic MEMS/circuits technology with VLSI and three layers of polysilicon thin films. The circuitry is consisted of sinusoidal oscillator, position sense circuits, and ΣΔ A/D converter. In order to achieve robust circuitry, suitable circuitry architecture was developed. Firstly, the sinusoidal oscillator with OTA-C structure is adopted, the oscillation condition and amplitude control of the structure are adjusted by tuning the gain of tranconductance. Since the structure contains only capacitors, thus, OTAs can be accomplished for CMOS implementation. Secondly, the position sensing circuit utilizes the differential readout for the reason that it is unsusceptible to EMI, supply variations and thermal noise. Finally, unlike traditional converters, the ΣΔ A/D converter requires high precision building blocks or correction mechanisms to obtain global precision. Note that ΣΔ A/D converters show very low sensitivity to the imperfections of the circuitry, at the price of extensive use of digital signal processing. Therefore, these architectures are adequate to achieve high-resolution A/D conversion in VLSI technologies; furthermore it is more suitable for implementing fast digital circuits than accurate analog circuits. Finally, the simulation of 2nd order ΣΔ modulator using SIMULINK® is conducted by taking account of most of the sigma-delta modulator non-idealities. The simulation can be used to observe the quantitative error of the designed system. By designing a single loop, single bit, 2nd order ΣΔ modulator, we are able to achieve effective resolution of 16 bits.