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trond

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Re: question about oscillators
Reply #15 - Aug 19^th, 2005, 9:00am

Thanks for the various references.
I agree that Demir's work is difficult to understand. I have had a look at the papers posted here and at a quick look at the book "Designer's Guide to High Purity Oscillators", but the process of learning is slow.

Please let me state a simple question. In switched-capacitor integrators the dynamic range is mainly determined by the kT/C noise. For example we have, DR=V_sw²*OSR*C_sampling/8/k/T.
I understand that in oscillators the dominant noise source is phase and jitter noise. Then, could we write the same expression for DR for ring-oscillators? For example the noise power for a 3-stage ring oscillator is given as |V_{n_tot}|²=8kT*2/(8gm)*(w_o/dw)². This is from Razavi's "A Study of Phase Noise in CMOS Oscillators". So could we say the DR is then again the ratio if the input singal power to |V_{n_tot}|²? I am just trying to make more sense out of this by relating it to something I know, namely SC circuits.

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ywguo

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Re: question about oscillators
Reply #16 - Aug 22^nd, 2005, 2:03am

Paul,

T.Weigandt's work focuses in time domain, too. I studied his thesis when I prepare my master thesis.

Weigandt's work only studied relative simple factors. He ignored something like correlation.

McNeill's work is more thoroughful. It also studies the noise of VCOs in open loop or that in closed loop. I think McNeill's work is more important than Weigandt's.

Best regards,
Yawei

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ywguo Community Fellow Offline Posts: 943 Shanghai, PRC	Re: question about oscillators Reply #17 - Aug 22^nd, 2005, 2:18am Svensl, The phase noise or jitter is noise in phase domain or timing domain. The VCO's DR is not the ratio of the phase noise to input power. Because the input power is the amplitude of the signal. Best regards, Yawei
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Frank Wiedmann

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Re: question about oscillators
Reply #18 - Aug 22^nd, 2005, 5:26am

Paul,

Demir explains in his paper http://home.ku.edu.tr/~aldemir/pubs/tcas001.pdf why he considers Hajimiri's method to be flawed, please refer to the next-to-last paragraph of section III. However, it might still be the case that Hajimiri's conjecture for orthogonally decomposing the perturbation into components that generate phase and amplitude deviations is a reasonably good approximation for many practical oscillator circuits. After all, the results that Hajimiri presents in his papers (e.g. http://www.chic.caltech.edu/Publications/general_full.PDF) seem to match reality pretty well. In order to really judge on this, it would probably be useful if one could get hold of Demir's reference [20] or maybe even try to contact Demir and/or Hajimiri themselves. Perhaps Jitter Man also has some additional insights on this subject.

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Paul Community Fellow Offline Posts: 351 Switzerland	Re: question about oscillators Reply #19 - Aug 22^nd, 2005, 6:50am Frank, I was not aware that this consideration was established in one of Demir's papers. Thanks for the information. Indeed it would be nice to see the development in the referenced paper, but it doesn't seem to be in the public domain. Paul
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Jitter Man

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Am I? Or am I so
sane that u just
blew your mind?

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Re: question about oscillators
Reply #20 - Aug 22^nd, 2005, 1:47pm

Anybody that has looked closely at Hajimiri's work from the CAD side of the world points out the flaws in the decomposition he uses. However, in most cases his decomposition, while not technically correct, gives reasonable results. However, in his paper on ring oscillators his claim that symmetry in the signals prevents flicker noise up conversion is completely false. And it is wrong for a completely different reason than problems in the decomposition.

For more information, see http://www.designers-guide.org/Forum/?board=rfsim;action=display;num=1094680012;....

Jitter Man

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Ken Kundert Global Moderator Offline Posts: 2386 Silicon Valley	Re: question about oscillators Reply #21 - Aug 23^rd, 2005, 8:56am You can find On the Validity of Orthogonally Decomposed Perturbations in Phase Noise Analysis by Demir and Roychowdhury here ... http://www.designers-guide.org/doc/1998-Phase-Noise-Orthogonal-TM.pdf -Ken
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Paul Community Fellow Offline Posts: 351 Switzerland	Re: question about oscillators Reply #22 - Aug 23^rd, 2005, 11:11am Jitter Man, Ken, thanks for the enlightening information. Paul
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Frank Wiedmann

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Re: question about oscillators
Reply #23 - Jan 30^th, 2007, 11:21am

I have just found out that there is a paper by Geoffrey Coram in which he presents a simple example showing that the orthogonal decomposition yields the wrong result. For me, it was much easier to understand than Demir's paper. It does not seem to be available for free download, but the exact reference can be found at http://ieeexplore.ieee.org/search/freesrchabstract.jsp?arnumber=933331&isnumber=....

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loose-electron Senior Fellow Offline Best Design Tool = Capable Designers Posts: 1638 San Diego California	Re: question about oscillators Reply #24 - Jan 30^th, 2007, 1:37pm I have to sit here and chuckle. Considering I know both Ali and John. As with a lot of academic papers, you need to look at the constraints of analysis.
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Geoffrey_Coram

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Re: question about oscillators
Reply #25 - Jun 28^th, 2007, 7:14am

Frank Wiedmann wrote on Jan 30^th, 2007, 11:21am:

I have just found out that there is a paper by Geoffrey Coram in which he presents a simple example showing that the orthogonal decomposition yields the wrong result. For me, it was much easier to understand than Demir's paper. It does not seem to be available for free download,

but you can PM me and I'll e-mail you a copy.

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If at first you do succeed, STOP, raise your standards, and stop wasting your time.

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Paul Geraedts Community Member Offline GIGO Posts: 60 Enschede, Netherlands	Re: question about oscillators Reply #26 - Oct 25^th, 2007, 12:27pm Hi everybody, I think this paper will be an interesting addition to this thread. In this paper both Demir's and Hajimiri's theory is applied and the results are compared. http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=1167539 Paul
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Frank Wiedmann Community Fellow Offline Posts: 678 Munich, Germany	Re: question about oscillators Reply #27 - Oct 25^th, 2007, 11:41pm Thanks for this reference. As Google reveals, the paper is available for free download at http://www.sigda.org/Archives/ProceedingArchives/Iccad/Iccad2002/04a_1.pdf.
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