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PLL BW measurement (Read 5984 times)

raja.cedt Senior Fellow Offline Posts: 1516 Germany	PLL BW measurement Nov 08^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.
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Mayank Community Fellow Offline Posts: 334	Re: PLL BW measurement Reply #1 - 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.
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raja.cedt Senior Fellow Offline Posts: 1516 Germany	Re: PLL BW measurement Reply #2 - 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.
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love_analog

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Re: PLL BW measurement
Reply #3 - 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.

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