一种改进交叉耦合晶体振荡器

Enhanced Cross-Coupled Crystal Oscillator

设计了一种改进的差分输出晶体振荡器,该振荡器在一般交叉耦合结构的基础上,通过加入RC高通滤波器来改良电路的相位噪声。分析了该RC滤波器对电路的影响并给出了优化方法。基于0.25μm标准CMOS工艺模型的仿真结果表明,该滤波器可有效滤除经过上变频会成为载波附近相位噪声的低频噪声(特别是1/f噪声)。采用普通4MHz晶体谐振器,该振荡器相位噪声可以达到-130.1dBc@100Hz。

This paper introduces an enhanced differential-output crystal oscillator. Based on common crosscoupled oscillators, we add additional RC High-Pass Filters （HPF） to reduce circuit＇s near carrier phase noise. The paper analyses the influence of the RC HPF and gives a way to optimize the circuit. Simulations based on 0. 25 μm standard CMOS process models show that the HPF can effectively decrease low frequency noise, especially 1/f noise, which will be up-converted to near carrier phase noise though Phase Modulation. When using mostly ordinary 4 MHz quartz resonators, phase noise reaches as low as -130.1 dBc at 100 Hz.