Abstract With the development of wireless communication,a low cost,high frequency accuracy,low phase noise,fully integrated crystal oscillator meets great market.A fully integrated DCXO is able to adjust its frequency by digitally switching its capacitor bank.The base station keeps broadcasting the frequency control burst (FCB)on the frequency control channel.The handheld terminal then uses this FCB to generate the frequency error signal to control the DCXO.For this reason,DCXO is valuable to substitute the high-cost TCXO/VCTCXO. The XO in home market is booming for a long time.For this purpose,a lot of work about theoretic research and circuit implement are carried out. Firstly,this work gives a quick preview on the XO research field on abroad and points out the advantage of the DCXO compared to the traditional TCXO/VCTCXO,with an eye on the difficulties of the DCXO design.Then based on the DVB Tuner application,phase noise specification has been analyzed. Secondly,an overview of several types of crystal oscillator is provided.A Santos topology is presented here for its good phase noise.Basic crystal oscillation theory is analyzed and all the ideal and non-ideal features are discussed. And then,a 14-bit DCXO based on Santos topology is presented.Small and large signal analyses are given.A deterministic methodology is introduced through the large signal model. Finally,the layout considerations and measurement results are given. The chip area is 0.4mm2 in a 0.18-um CMOS process,consumes 1mA current under 1.8V supply voltage.The measured phase noise results are -139 dBc/Hz at 1 kHz and -151 dBc/Hz at 10 kHz frequency offset, respectively.The DCXO achieves 35 ppm tuning range and ~0.04 ppm frequency step.The frequency variation is t7 ppm across the temperature range from-40℃to80C. Key words:DCXO,TCXO,phase noise,automatic amplitude control, delta-sigma modulation,supply pushing VV Abstract With the development of wireless communication, a low cost, high frequency accuracy, low phase noise, fully integrated crystal oscillator meets great market. A fully integrated DCXO is able to adjust its frequency by digitally switching its capacitor bank. The base station keeps broadcasting the frequency control burst (FCB) on the frequency control channel. The handheld terminal then uses this FCB to generate the frequency error signal to control the DCXO. For this reason, DCXO is valuable to substitute the high-cost TCXO/VCTCXO。 The XO in home market is booming for a long time. For this purpose, a lot of work about theoretic research and circuit implement are carried out. Firstly, this work gives a quick preview on the XO research field on abroad and points out the advantage of the DCXO compared to the traditional TCXO/VCTCXO, with an eye on the difficulties of the DCXO design. Then based on the DVB Tuner application, phase noise specification has been analyzed. Secondly, an overview of several types of crystal oscillator is provided. A Santos topology is presented here for its good phase noise. Basic crystal oscillation theory is analyzed and all the ideal and non-ideal features are discussed. And then, a 14-bit DCXO based on Santos topology is presented. Small and large signal analyses are given. A deterministic methodology is introduced through the large signal model. Finally, the layout considerations and measurement results are given. The chip area is 0.4mm2 in a 0.18-μm CMOS process, consumes 1mA current under 1.8V supply voltage. The measured phase noise results are –139 dBc/Hz at 1 kHz and –151 dBc/Hz at 10 kHz frequency offset, respectively. The DCXO achieves 35 ppm tuning range and ~ 0.04 ppm frequency step. The frequency variation is ±7 ppm across the temperature range from -40℃ to 80℃. Key words: DCXO, TCXO, phase noise, automatic amplitude control, delta-sigma modulation, supply pushing