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Design >> RF Design >> Linearizing Varactor for LC Oscillator
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Message started by mtp3 on Apr 4^th, 2012, 10:32am

Title: Linearizing Varactor for LC Oscillator
Post by mtp3 on Apr 4^th, 2012, 10:32am

Hi!

I am trying to design an LC oscillator (cross coupled NMOS) to oscillate at 2GHz. I have tried some of the commonly used topologies like NMOS(D=S, Bulk=gnd) or PMOS(B=D=S) and PMOS(D=S,B=Vdd).

The problem is when I sweep the varactor control codes(at the DC point of output) for frequency steps/behviour, the resulting frequency does not remain constant for some steps (or code values) rather it jumps back and forth in magnitudes of 2-4MHZ. I am confused as to why this is happening.

It would be great if some could propose a solution to this issue :-/

Title: Re: Linearizing Varactor for LC Oscillator
Post by raja.cedt on Apr 5^th, 2012, 12:28am

may be useful

Method for a Constant Loop Bandwidth in LC-VCO PLL Frequency Synthesizers

Title: Re: Linearizing Varactor for LC Oscillator
Post by mtp3 on Apr 5^th, 2012, 5:01am

Thanks for the reply, will look in to it.