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Design >> RF Design >> Noise contribution from a VCO
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Message started by chen on Oct 14^th, 2004, 5:31pm

Title: Noise contribution from a VCO
Post by chen on Oct 14^th, 2004, 5:31pm

Hi.
I am not experienced in VCO design so here is a quick question: If I design a 3.6Ghz cross-coupled complementary LC VCO in CMOS with phase noise the most important matrix, normally which would dominate the noise? (current source, LC-tank(spiral ind and PMOS varactor, MOS) I ask this cause I wanna know I am going in the right direction when optimising the design.
Thank you.

Title: Re: Noise contribution from a VCO
Post by chen on Oct 21^st, 2004, 10:00am

Just to follow up on my previous post, the more I read the IEEE papers, the more unsure I am about the answer. In papers like "Tail Current Noise Suppression in RF CMOS VCOs", JSSC Vol 37 nos 3, current source is identified as the main culprit for noise while in papers like the one in [Hajimiri JSSC 01 Vol36], tail current noise source is very small. Maybe it is just the difference in optimization approach that yield such a great difference?
(one report noise summary @ 3MHz the other @ 600khz so that partly explain the different. But still, there are many literature that claims that the tail current source dominates the noise at 1/f^3 and 1/f^2 region and the data in Hajimiri paper seems to suggest otherwise....)