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 phase noise of ring oscillator using spectre (Read 57195 times)
 Mayank Community Fellow Offline Posts: 334 Re: phase noise of ring oscillator using spectre Reply #15 - Nov 23rd, 2009, 5:04am   Hello pancho,    Gotcha,  So summing up our discussions so far,     1.  For +ve Offset Frequencies, Lssb = Lusb,     2.  For -ve Offset Frequencies, Lssb = Llsb...     3.  Cadence plots Lssb, which is Lusb or Llsb depending on whether the offset specified as +1 or -1. defualt being +1, it is Lusb.     4.  pnoise modulated gives all components separately     5.  pnoise jitter plots true Sphi which should be equal to PM noise from pnoise modulated  .Am i correct so far ??I simulated with HB-PSS/augmented-PNOISE and i am attaching the waveforms obtained for LSB, USB, AM & PM noise plots....In HB-PSS/AUGMENTED-PNOISE, To my surprise, AM plot is coming too close to the PM plot....Also LLSB is totally wierd and nothin similar to LUSB...Totally confused by the results..... Back to top IP Logged
 pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless Re: phase noise of ring oscillator using spectre Reply #16 - Nov 23rd, 2009, 5:19am   Mayank wrote on Nov 23rd, 2009, 5:04am:     1.  For +ve Offset Frequencies, Lssb = Lusb,     2.  For -ve Offset Frequencies, Lssb = Llsb...     3.  Cadence plots Lssb, which is Lusb or Llsb depending on whether the offset specified as +1 or -1. defualt being +1, it is Lusb.Am i correct so far ?? I can't understand your expressions.Mayank wrote on Nov 23rd, 2009, 5:04am:In HB-PSS/AUGMENTED-PNOISE, To my surprise, AM plot is coming too close to the PM plot....Also LLSB is totally wierd and nothin similar to LUSB...Totally confused by the results..... I think you treat LLSB and AM noises wrongly.Maybe your AM noise is LLSB and your LLSB is AM noise.Confirm your AM noise and LLSB.Do you have Agilent GoldenGate(4.3.6 or 4.3.7) or Agilent RFDE(ADSsim 2008U2 or 2009) ? Back to top IP Logged
 Mayank Community Fellow Offline Posts: 334 Re: phase noise of ring oscillator using spectre Reply #17 - Nov 23rd, 2009, 6:33am   Hello Pancho,                       At first i also thought so.....But i rechecked it twice....The image i attached previously is correct...I plotted USB,LSB, AM & PM from pnoise_modulated of Direct plot Form.....It is showing LLSB wierdly.....& it shows PM Noise = AM Noise ....Totally wierd !!!However, the plots without augmented pnoise analysis are the ones i am attaching now....Is this a bug in spectreRF that it exchanges AM & LLSB plots OR is it a bug in augmented pnoise analysis OR is it really possible ?   i have no clue....And i dont have access to any tools from Agilent...  :(mayank Back to top IP Logged
 pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless Re: phase noise of ring oscillator using spectre Reply #18 - Nov 23rd, 2009, 6:39am   Mayank wrote on Nov 23rd, 2009, 6:33am:Is this a bug in spectreRF that it exchanges AM & LLSB plots OR is it a bug in augmented pnoise analysis OR is it really possible ?   i have no clue.... Post your questions in http://www.cadence.com/Community/forums/33.aspxI think these are bugs and augmented pnoise is still unreliable and suspicious.. Back to top IP Logged
 Mayank Community Fellow Offline Posts: 334 Re: phase noise of ring oscillator using spectre Reply #19 - Nov 23rd, 2009, 9:02pm   Hello Pancho,                    Thanx for all the help and your quick replies....They helped a lot....One of my best discussions on the forum....mayank Back to top IP Logged
 pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless Re: phase noise of ring oscillator using spectre Reply #20 - Nov 24th, 2009, 3:21am   Mayank, again see the followings.http://www.designers-guide.org/Forum/YaBB.pl?num=1241894034/12#12http://www.designers-guide.org/Forum/YaBB.pl?num=1241894034/23#23Originally Lorentzian Spectrum Models were derived in the absence of flicker noise.In the absence of 1/f noise, it is well known that phase noise should show a Lorentzian spectrum. We can easily apply this to evaluation of the phase noise characteristics.But modeling as Lorentzian Spectrum does not yield meaningful results if 1/f noise is present.There is an issue for the use of the Lorentzian spectrum in the presence of 1/f noise.PM noise can become very large at low offset because of continued accumulation of phase close to the carrier, so it could go above 0dBc/Hz. Properly, units of PM noise should be "dBrad/Hz".SideBand Noise, LSSB(f) is an approximation combining AM and PM noise, so LSSB(f) could also go above 0dBc/Hz at low offset especially in the presence of 1/f noise.Your following HB-PSS/AUGMENTED-PNOISE results are all completely flat for small offset frequency region.http://www.designers-guide.org/Forum/YaBB.pl?num=1050465395/15#15Even PM noise is also completely flat. These results are very suspicious.Such completely flat phase noise reminds me phase noise of Agilent MDS or Agilent earlyday's ADS which underestimated phase noise for small offset frequency region.See "Phase Noise Overview" of "Chapter 10: Oscillator Noise Simulation" in the following.http://cp.literature.agilent.com/litweb/pdf/ads15/cktsim/index.htmlI think Cadence Spectre's HB-PSS/AUGMENTED-PNOISE is still very suspicious.Apart from Spectre's HB-PSS/AUGMENTED-PNOISE, some analytical models have been proposed for phase noise with flicker noise.These decompose the model into a Lorentzian for the white noise sources and Gaussian for the flicker noise source.So these share the property of the Lorentzian spectrum so that it has an integrated area of one ; it conserves the overall power of the noiseless oscillator,     and has a finite value as the offset frequency approaches zero.At small offsets the spectrum looks like a Gaussian when dominated by flicker noise ; at larger offsets 1/f3 behavior is seen, followed by 1/f2 behavior.[1] F. Herzel, "An Analytical Model for the Power Spectral Density of a Voltage-Controlled Oscillator and Its Analogy to the Laser Linewidth Theory", IEEE Transactions on Circuits and Systems . I: Fundamental Theory and Applications, vol. 45, pp. 904.908, Sept. 1998.[2] G. V. Klimovitch, "Near-Carrier Oscillator Spectrum Due to Flicker and White Noise", Proc. of ISCAS 2000, IEEE International Symposium on Circuits and Systems, Geneva, pp. I-703.706, 2000.[3] G. V. Klimovitch, "A Nonlinear Theory of Near-Carrier Phase Noise in Free-Running Oscillators", Proc. of Third IEEE International Conference on Circuits and Systems, Caracas, pp T80/1.6, 2000.[4] A. Demir, "Phase Noise in Oscillators: DAEs and Colored Noise Sources", Proc. of ICCAD-98, pp. 170.177, 1998. Back to top « Last Edit: Nov 25th, 2009, 12:41am by pancho_hideboo »     IP Logged
 Mayank Community Fellow Offline Posts: 334 Re: phase noise of ring oscillator using spectre Reply #21 - Nov 25th, 2009, 12:14am   Hello Pancho,                    I want to reserarch more on this so that i can resolve the issue....Could you provide me the 3rd paper you mentioned -- Quote:[3] G. V. Klimovitch, "A Nonlinear Theory of Near-Carrier Phase Noise in Free-Running Oscillators", Proc. of Third IEEE International Conference on Circuits and Systems, Caracas, pp T80/1.6, 2000. It would be very helpful....   Also i wanted to ask Can AM noise become equal to PM noise at such low offsets as 10kHz ??   Have you verified any silicon vs. CAD results so that i can know what matches silicon results better ?? -- the flattened Pnoise plot  OR  the actual > 0dB plot  ??mayank Back to top IP Logged
 pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless Re: phase noise of ring oscillator using spectre Reply #22 - Nov 25th, 2009, 1:45am   Mayank wrote on Nov 25th, 2009, 12:14am:Also i wanted to ask Can AM noise become equal to PM noise at such low offsets as 10kHz ?? I don't think so.Mayank wrote on Nov 25th, 2009, 12:14am:Have you verified any silicon vs. CAD results so that i can know what matches silicon results better ?? -- the flattened Pnoise plot  OR  the actual > 0dB plot  ?? In actual Measurement using Actual Instruments, LSSB(f) never go above 0dBc, while PM(f) can be go above 0dBrad/Hz.Using Vector Signal Analyzer, we can evaluate AM and PM noises. https://forums.tm.agilent.com/community/viewtopic.php?f=33&t=2504https://forums.tm.agilent.com/community/download/file.php?id=570I have Agilent 4352B VCO/PLL Signal Analyzer and 89400 & 89600 Vector Signal Analyzer.I don't have E5052B which is new replacement of 4352B.Agilent E5052B Signal Source Analyzer can measure AM noise directly.http://cp.literature.agilent.com/litweb/pdf/5989-7273EN.pdf Back to top « Last Edit: Nov 25th, 2009, 4:10am by pancho_hideboo »     IP Logged
 Mayank Community Fellow Offline Posts: 334 Re: phase noise of ring oscillator using spectre Reply #23 - Nov 25th, 2009, 9:08pm   Heloo Pancho,                       The Document on Choosing Phase Noise Techniques by Agilent was quite helpful.....            But i didnt exactly understand this concept....PM Noise refers to Phase Modulation due to noise.....& Phase Noise is a cumulative effect of both AM & PM.....Then shouldn't Phase Noise also go higher than 0 dBrad/Hz if one of it's components are going above 0dBrad/Hz .....        If LSSB doesnt go above 0dBc , then is it the correct representation of Phase Noise ??--mayank. Back to top IP Logged
 pancho_hideboo Senior Fellow Offline Posts: 1424 Real Homeless Re: phase noise of ring oscillator using spectre Reply #24 - Nov 25th, 2009, 10:36pm   Mayank wrote on Nov 25th, 2009, 9:08pm:Then shouldn't Phase Noise also go higher than 0 dBrad/HzdBc/Hz if one of it's components are going above 0 dBrad/Hz ..... SideBand Noise, LSSB(f) is an approximation combining AM and PM noise, so in simulation using current EDA Tool, LSSB(f) could also go above 0 dBc/Hz at low offset especially in the presence of 1/f noise.Mayank wrote on Nov 25th, 2009, 9:08pm:If LSSB doesnt go above 0dBc, then is it the correct representation of Phase Noise ?? What I can say surely is "Cadence Spectre's HB-PSS/AUGMENTED-PNOISE is very suspicious".That's all.Modeling as Lorentzian Spectrum does not yield meaningful results if 1/f noise is present.Again see the followings.http://www.designers-guide.org/Forum/YaBB.pl?num=1241894034/12#12http://www.designers-guide.org/Forum/YaBB.pl?num=1241894034/23#23Also see last append by "RFMEMS" in http://www.cadence.com/community/forums/T/12466.aspxEven RFMEMS has a doubt now.I think results of HB-PSS/Pnoise without Augmented is rather proper. But even using Agilent GoldenGate Simulator, LSSB for small offset frequency can not be matched to actual measurement well. Back to top « Last Edit: Nov 26th, 2009, 3:10am by pancho_hideboo »     IP Logged
 Mayank Community Fellow Offline Posts: 334 Re: phase noise of ring oscillator using spectre Reply #25 - Dec 10th, 2009, 10:17pm   Hi Pancho,                I am too confised at this stage                 Just confirming Once Again :----1. According to the doc you poited out on Choosing PhaseNoise Techniques by Agilent, I should trust SΦ/2 values instead of LUSB. So does the true SΦ plot (given by pnoise jitter option in Direct Plot Main Form of cadence as pointed out by you in your post  http://www.designers-guide.org/Forum/YaBB.pl?num=1244213153/6#6) never go above 0 dBc/Hz ??2.  If you have compared Silicon vs CAD results, which is  a better approximation to actual measurements out of these  ----->  1. Augmented Pnoise  ??2. SΦ/2 below linewidth & LΦ after Linewidth  ??3.  Only LUSB plot of vanilla Pnoise  ??--  mayank. Back to top IP Logged