壓控石英振盪器精準頻率控制之研究

Abstract

本論文旨在使用金氧半製程研究積體化壓控石英振盪器，並能夠精準控制其頻率表現。其中使用HSPICE傅立葉分析MOS可變電容的大信號電容行為，由頻率預估公式可成功預估頻率調諧曲線，與實測最大誤差小於3ppm，以此克服HSPICE模擬石英等高品質因素電路，頻率模擬解析度不足而無法預知頻率表現的情形。利用此預估方法與負電阻起振分析，依照不同應用並配合石英晶體規格，設計出兩積體化的壓控石英振盪器；首先實現寬頻可調壓控石英振盪器，可調頻率 350ppm，相位雜訊表現-80dBc/Hz@10Hz，具快速起振285us，適用於短距離通訊的頻率參考源。另ㄧ個實現能校正室溫頻率偏移至1ppm以內，且低電流消耗(包含輸出級713uA)，相位雜訊表現 -90dBc/Hz@10Hz，與溫度補償電路整合在溫度 變化下，可補償頻率偏移小於1ppm，達成一個精準控制頻率的溫度補償壓控石英振盪器，提供行動通訊精準的頻率參考源。

The purpose of this thesis is to develop a voltage controlled crystal oscillator (VCXO) with precise frequency control using CMOS process. Using HSPICE fourier analysis to explain large signal behavior of MOS Varactor and adopting ideal lossless tank formula can predict frequency tuning curve. The maximum error between calculation and measurement is within 3ppm with all parasitic effects taken into account. By ways of frequency prediction, two integrated VCXO are implemented, which apply to different applications. Firstly, a widely-tuning VCXO with tuning range of 350ppm and fast start-up of 285us is fabricated with the capability of frequency modulation. It is suitable for short range wireless transmitter. The phase noise performance is -80dBc/Hz@10Hz. Furthermore, instead of wide tuning a VCXO with low power dissipation and low phase noise performance, which can calibrate frequency within 1ppm accuracy at room temperature, is proposed. The current consumption of overall oscillator circuit is only 713uA. The measured phase noise is -90dBc/Hz@10Hz. Combining with temperature compensated circuit, the oscillator can be compensated within 1ppm accuracy from -30 degree to 80 degree. This design is intended for application in mobile communication.