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Design >> Mixed-Signal Design >> about VCO modeling
https://designers-guide.org/forum/YaBB.pl?num=1166581661

Message started by jeffyan on Dec 19^th, 2006, 6:27pm

Title: about VCO modeling
Post by jeffyan on Dec 19^th, 2006, 6:27pm

hi all,
we usesually model the voltage-controlled oscillator like this:

f=Kvco * Vc.

and Kvco is extracted by a dc sweep of Vc. but i want to question that whether Kvco is frequency dependent? if yes, why we ignore it?
thanks,
jeff

Title: Re: about VCO modeling
Post by ywguo on Dec 21^st, 2006, 8:24pm

Jeff,

Do you want to make the model too complex?

Obviously, probably the PLL is not stable if Kvco is frequency dependent.

BG
Yawei

Title: Re: about VCO modeling
Post by jeffyan on Dec 21^st, 2006, 9:05pm

HI,
i think, the reason why we ignore the frequency-depedance of Kvco, is Kvco(f) is of a low-pass property, and its cut-off frequency is larger than PLL' bandwidth.
this is my own opinion for your consideration.
jeff

Title: Re: about VCO modeling
Post by ywguo on Dec 25^th, 2006, 1:38am

Jeff,

I don't understand why Kvco is of a low-pass property? Would you please explain it or present an example?

Thanks
Yawei