The Designer's Guide Community
Forum
Welcome, Guest. Please Login or Register. Please follow the Forum guidelines. Oct 23rd, 2017, 3:45pm
  HomeHelpSearchLoginRegisterPM to admin  
 
Pages: 1
Send Topic Print
Simulation of DJ using SpectreRF (Read 6844 times)
Visjnoe
Senior Member
****
Offline



Posts: 233

Simulation of DJ using SpectreRF
Aug 20th, 2007, 11:55pm
 
Dear all,

can SpectreRF be used to simulate deterministic jitter (DJ), e.g. due to power supply ripple/noise?
Will these show up as spurs in the phase noise profile of a clock signal?

The only alternative (that works) that I can come up with to simulate DJ is to run a transient simulation and to look at the period + deviations of the signal under investigation.

Has anybody used SpectreRF for simulating DJ?


Regards

Peter
Back to top
 
 
View Profile   IP Logged
Frank Wiedmann
Community Fellow
*****
Offline



Posts: 635
Munich, Germany
Re: Simulation of DJ using SpectreRF
Reply #1 - Aug 21st, 2007, 2:56am
 
Sampled pxf analysis is the method of choice for this. You get the jitter by dividing the result by the slope (derivative) of the signal at the crossing point. I have used this method extensively in the past (using tdnoise and special noise sources at a time when sampled pxf did not yet exist) and the results have always been very close to those of transient simulations. Sampled pac analysis is still rather buggy at the moment but sampled pxf seems to work ok, probably because it is in some way part of the tdnoise analysis.
Back to top
 
 
View Profile WWW   IP Logged
Frank Wiedmann
Community Fellow
*****
Offline



Posts: 635
Munich, Germany
Re: Simulation of DJ using SpectreRF
Reply #2 - Aug 23rd, 2007, 12:05am
 
An additional hint: in transient analysis, the jitter is probably measured most easily by plotting the result with the eyeDiagram calculator function and then measuring the jitter with the crosshair markers.
Back to top
 
 
View Profile WWW   IP Logged
wwm101
Junior Member
**
Offline



Posts: 20
china
Re: Simulation of DJ using SpectreRF
Reply #3 - Oct 8th, 2008, 7:25pm
 
Frank Wiedmann wrote on Aug 23rd, 2007, 12:05am:
An additional hint: in transient analysis, the jitter is probably measured most easily by plotting the result with the eyeDiagram calculator function and then measuring the jitter with the crosshair markers.

can we extract DJ and RJ separately from the total jitter?
Back to top
 
 
View Profile wwm101 weiming022002@yahoo.com   IP Logged
Frank Wiedmann
Community Fellow
*****
Offline



Posts: 635
Munich, Germany
Re: Simulation of DJ using SpectreRF
Reply #4 - Nov 1st, 2008, 2:30pm
 
The method described above simulates the deterministic jitter due to disturbances on the power supply. For the deterministic jitter due to intersymbol interference, do a transient simulation with a representative data signal at the input and plot the output signal with the eyeDiagram calculator function. For the simulation of random jitter due to device noise, see http://www.designers-guide.org/Forum/YaBB.pl?num=1224609785.
Back to top
 
 
View Profile WWW   IP Logged
Jacki
Senior Member
****
Offline



Posts: 167

Re: Simulation of DJ using SpectreRF
Reply #5 - Sep 27th, 2017, 9:56am
 
Hi Frank,

   Thank you for your explanation of DJ simulation. How about an oscillator with a modified power supply, how to simulate the jitter?
Back to top
 
 
View Profile   IP Logged
Frank Wiedmann
Community Fellow
*****
Offline



Posts: 635
Munich, Germany
Re: Simulation of DJ using SpectreRF
Reply #6 - Sep 28th, 2017, 12:46am
 
It's not quite clear for me what you mean by "modified power supply". However, I think that you should be able to use the same method for oscillators as well. Just select the Oscillator mode in the PSS setup form.
Back to top
 
 
View Profile WWW   IP Logged
Jacki
Senior Member
****
Offline



Posts: 167

Re: Simulation of DJ using SpectreRF
Reply #7 - Sep 28th, 2017, 5:10am
 
Hi Frank,

   Thank you for your reply. Maybe I don't describe the problem clearly. For example, I have a ring oscillator, but the power supply is not clean (i.e. switched-capacitor DC converter or the ripple due to large current drop). I read some documents, your threads, and Ken's paper about the bang-bang noise. I think the jitter due to power supply should belong to deterministic jitter. I am not sure if we can simulate the DJ of an oscillator due to power supply ripple directly by PSS and PNoise because I am afraid PSS will not be converged since it is like a two-tone system. We can turn off the device noise and just look at the DJ due to the power supply ripple.
Regarding the PXF simulation you mentioned in this thread, do you know if there is any application notes or more detailed descriptions. It looks oscillator is an autonomous system, but when the jitter is generated by power supply, it becomes a kind of driven circuit?
Thank you.
Jacki
Back to top
 
 
View Profile   IP Logged
Jacki
Senior Member
****
Offline



Posts: 167

Re: Simulation of DJ using SpectreRF
Reply #8 - Sep 28th, 2017, 5:39am
 
By the way, Frank, you talk a lot about the eye diagram plot. Would it be possible to evaluate an oscillator by eye diagram as well, just like a driven circuit?
Thank you.
Back to top
 
 
View Profile   IP Logged
Jacki
Senior Member
****
Offline



Posts: 167

Re: Simulation of DJ using SpectreRF
Reply #9 - Sep 28th, 2017, 9:58am
 
Hi Frank,

   I see you talk about the sampled PXF, what is the unit of the output from the sampled PXF? Does the transfer function has the output unit as sec/V? Because you say we can get the jitter by dividing the transfer function results by the slope of the output signal (I guess PSS can do it, do we need to define the time event as in PNoise simulation?). I think the slope is dv/dt, if so, the output should have the unit square(sec)/V? Please correct me, I am new to use the PXF transfer function. Thank you.
Back to top
 
 
View Profile   IP Logged
Frank Wiedmann
Community Fellow
*****
Offline



Posts: 635
Munich, Germany
Re: Simulation of DJ using SpectreRF
Reply #10 - Sep 29th, 2017, 2:18am
 
The pxf transfer function has the unit V/V. When you divide by the signal slope (V/s), you get the transfer function from power supply ripple to output jitter in s/V. If you use the pxf analysis, you should not add an additional ripple to the power supply voltage. As a consequence, pss convergence should not be a problem because you only have a single tone (the oscillator signal).

You can of course also use the eye diagram. You will have to be careful to specify the correct time period for the eye diagram plot, however, because this may strongly influence your result.
Back to top
 
 
View Profile WWW   IP Logged
Jacki
Senior Member
****
Offline



Posts: 167

Re: Simulation of DJ using SpectreRF
Reply #11 - Sep 29th, 2017, 4:08am
 
Hello Frank,

   Thank you. It seems the sampled PXF gives the sensitivity of the output jitter to the supply ripple, and it is a small-signal condition. Since the result from PXF divided by the slope dv/dt has the unit sec/V, how to calculate the jitter at the output due to the power supply ripple? Also is the PXF giving the transfer function in Frequency domain? If so, it should be a frequency dependent transfer function (at least plot from 0 Hz to f0, f0 is the beating frequency)? how to choose the value from the PXF result?
Assume we already know the sensitivity for the output jitter to supply ripple, but the ripple on the power supply is an unknown value, how to calculate the jitter? I am guessing if I need to average the ripple value, and use the averaged ripple voltage multiply the sensitivity to get the "RMS jitter".
   Please give me a hint, and I hope I will not bother you on this problem again. Thank you. Have a nice weekend.
Back to top
 
 
View Profile   IP Logged
Frank Wiedmann
Community Fellow
*****
Offline



Posts: 635
Munich, Germany
Re: Simulation of DJ using SpectreRF
Reply #12 - Sep 29th, 2017, 4:51pm
 
Back to top
 
 
View Profile WWW   IP Logged
Jacki
Senior Member
****
Offline



Posts: 167

Re: Simulation of DJ using SpectreRF
Reply #13 - Sep 30th, 2017, 11:17pm
 
Thank you very much Frank. It seems PXF can be used to estimate a known power supply ripple with absolute frequency. I think the transfer function divided by the slope at the transition time gives the transfer function from voltage to jitter, and if we want to know the jitter, we need to know the amplitude of the ripple first. As you mentioned, for an unknown ripple, it is better to run a transient simulation. Have a good day.
Regards, Jacki
Back to top
 
 
View Profile   IP Logged
Pages: 1
Send Topic Print
Trouble viewing this site? Copyright © 2002-2014 Designer's Guide Consulting. 'Designer's Guide' is a registered trademark of Designer's Guide LLC. All rights reserved.

Our colleges are not as safe as they seem. Sexual assault is pervasive and the treatment of the victim by the adminstration is often as damaging as the assault: Campus Survivors, Campus Survivors Forum.

Some of our other sites that you might find useful: QuantiPhy.