IEICE Electronics Express
Online ISSN : 1349-2543
ISSN-L : 1349-2543
LETTER
Current reused Colpitts VCO and frequency divider with quadrature outputs
Xincun JiFuqing HuangJianhui WuLongxing Shi
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JOURNAL FREE ACCESS

2011 Volume 8 Issue 4 Pages 239-244

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Abstract

A low power current reused Colpitts VCO and divide-by-two circuit is proposed in 0.18µm CMOS technology. The divider is stacked on top of a common drain gm-boosted differential Colpitts VCO to share DC current. A capacitance neutralization technique is used to compensate the miller effect of the parasitic gate-drain capacitance Cgd in the VCO, and improves the generated negative resistance and phase noise performance. The Colpitts VCO works at 4.293-4.513GHz, and can provide 2.147-2.257GHz quadrature outputs through the stacked divide-by-two circuit. The VCO circuit exclude the output buffer consumes 2.8mA at 1.8V supply voltage. The measured phase noise is -109dBc/Hz at 1MHz offset frequency when the VCO output is 4.513GHz.

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© 2011 by The Institute of Electronics, Information and Communication Engineers
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