用失配电容对提高数控LC振荡器调频率精度

Improving LC-based DCO frequency resolution using mismatched capacitor pairs

为了提高基于LC的数控振荡器(DCO)的调频精度,提出一种失配电容对跨接数控变容管结构。该结构利用2个失配电容对对CMOS变容管的最小有效变容值进行缩小变换,使得数字信号可控的最小电容值大大降低。为验证该结构,该文采用中芯国际(SMIC)0.18μm工艺库,在Spectre中对基于该文结构的数控振荡器在不使用ΣΔ调制技术的前提下进行仿真。实验结果表明:该文提出的数控变容结构能使中心频率为3.4 GHz的DCO实现3 kHz的调频精度,还能使调频精度的提高不依赖于工艺库特征尺寸。

A digitally controlled varactor structure was developed based on mismatched capacitor pairs to enhance the frequency resolution of LC-based digitally controlled oscillators（DCOs）.In the structure,the minimum switched capacitance of the CMOS varactor can be reduced,resulting in frequency resolution enhancement.A DCO based on the structure without SDM was implemented in SMIC0.18 and simulated in Spectre.The results show that the frequency resolution of the DCO with a central frequency of 3.4 GHz reaches 3 kHz without dependence on the feature sizes of the given process.