The Designer's Guide Community
Forum
Welcome, Guest. Please Login or Register. Please follow the Forum guidelines.
Mar 28th, 2024, 10:28am
Pages: 1
Send Topic Print
Spectral purity relation between oscillator and divided frequency. (Read 1367 times)
Jacki
Senior Member
****
Offline



Posts: 237

Spectral purity relation between oscillator and divided frequency.
Aug 28th, 2017, 1:03am
 
Hi all,

   I am calculating the spectral purity of the output of a ring oscillator. I am a little confused of the definition.
   I get the spec. of spectral purity of the output oscillating frequency of a DLL, based on the spec., I need to calculate the requirement of spectral purity the oscillator. For example, if the pre-scaler is 32, and it means the output frequency of the oscillator will be divided by 32 as the output of the DLL, how to do the calculation. By the way, the spec. is not given by phase noise, it is given by integrated energy in the given bandwidth, for example [-fm + f0, f0 + fm].
   If the oscillator has the frequency as fosc, and the output of the DLL is f0, and N = 32, the integration of the spectrum of the DLL output is from -fm + f0 to f0 + fm, how to build the equation between these two spec.?
   I writes my calculation below, correct me if I am wrong (by the way, if the noise contribution from the frequency divider is not much, we may skip its contribution).
   The integration of the oscillator frequency spectrum is from -32fm + fosc to fosc + 32fm, since it is the energy integration, not the SNR, I would think the spectral purity would be the same as the integration from -fm +f0 to f0 + fm. Any comments? Thank you.
Back to top
 
 
View Profile   IP Logged
Jacki
Senior Member
****
Offline



Posts: 237

Re: Spectral purity relation between oscillator and divided frequency.
Reply #1 - Aug 31st, 2017, 6:55am
 
Hi,

   I think I solve my problem since phase noise doesn't move. Thank you.
Back to top
 
 
View Profile   IP Logged
Pages: 1
Send Topic Print
Copyright 2002-2024 Designer’s Guide Consulting, Inc. Designer’s Guide® is a registered trademark of Designer’s Guide Consulting, Inc. All rights reserved. Send comments or questions to editor@designers-guide.org. Consider submitting a paper or model.