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Measurements >> RF Measurements >> PLL BW measurement
https://designers-guide.org/forum/YaBB.pl?num=1289222200

Message started by raja.cedt on Nov 8^th, 2010, 5:16am

Title: PLL BW measurement
Post by raja.cedt on Nov 8^th, 2010, 5:16am

hi, can any please tell me how to find BW in silicon
I know that Intersecting point of VCO phase noise and pll phase noise point is almost BW. Is this exact method or can any one please explain often how people measures?

Thanks.

Title: Re: PLL BW measurement
Post by Mayank on Nov 19^th, 2010, 5:22am

Quote:

Intersecting point of VCO phase noise and pll phase noise point is almost BW

approximately, yes.
You could tell by pll phase noise graph itself in most of the cases.

Title: Re: PLL BW measurement
Post by raja.cedt on Nov 19^th, 2010, 6:22am

hi mayank,
how can you say from overal PLL phase noise. I htink from where phase noise start falling (means the boundary between inband and outoff band noise), do you have any document for this

Thanks.

Title: Re: PLL BW measurement
Post by love_analog on Mar 3^rd, 2011, 2:04pm

To measure PLL BW, you put a refclock with a modulated sinewave input. So you are modulating the phase of the input refclock. Then you look at the output on the spectrum analyzer. You should see a spur at the same frequency as the phase modulation. The measure of the spur compared to the input refclock spur gives you a value for the attenuation. At att=-3db is where PLL BW is.