High Frequency Resolution DCO with Mismatched Capacitor Pairs

Depeng JIN
Guofei ZHOU
Yong LI
Shijun LIN
Li SU
Lieguang ZENG

Publication
IEICE TRANSACTIONS on Electronics   Vol.E93-C    No.2    pp.208-210
Publication Date: 2010/02/01
Online ISSN: 1745-1353
DOI: 10.1587/transele.E93.C.208
Print ISSN: 0916-8516
Type of Manuscript: LETTER
Category: Electronic Circuits
Keyword: 
digitally controlled oscillator,  digital phase locked loop,  digitally controlled switched,  

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Summary: 
The LC-based Digitally Controlled Oscillator (DCO) is one of the most important components of all digital phase locked loops. The performance of the loops is significantly determined by the DCO's frequency resolution. In order to enhance the frequency resolution, we propose a mismatched capacitor pairs based digitally controlled switched capacitance array, which dramatically reduces the minimum switched varactor capacitance. Furthermore, we implement a DCO based on our proposal in SMIC 0.18 µm and conduct simulation in Spectre. The simulation results show that the frequency resolution is enhanced compared with the existing methods.