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pancho_hideboo

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Augmented Pnoise of Cadence Spectre
May 09^th, 2009, 11:33am

Cadence claims about "Augmented Pnoise" of Cadence Spectre like following.
Quote:

We have improved Pnoise analysis for autonomous circuits with a new "augmented" mode.
Augmented Pnoise will give more accurate results for oscillators with large time constants.
In augmented Pnoise, the frequency-aware PPV method (rather than Floquet deflation) is used.
The new method gives a Lorentzian plot.
However, the price you pay is slower simulation speed.

http://www.cadence.com/Community/blogs/rf/archive/2008/07/29/why-do-shooting-and...
http://www.cadence.com/Community/blogs/rf/archive/2008/08/26/guidelines-for-simu...
http://www.cadence.com/Community/blogs/rf/archive/2009/05/01/enhanced-pnoise-alg...

To my regret, I can't access Cadence Spectre which supports "Augmented Pnoise".

Is there anyone who compared results of "Augmented Pnoise" of Cadence Spectre with Agilent GoldenGate or ADSsim, especially regarding phase noise in very small offset frequency region ?

"Augmented Pnoise" of Cadence Spectre truely can give good results ?

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ACWWong

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Re: Augmented Pnoise of Cadence Spectre
Reply #1 - May 12^th, 2009, 5:48am

We use "Augmented Pnoise" in our last design tape-out, it gave us more conservative (i.e. higher) estimation of phase noise than vanilla pnoise. This was especially true in our VCO (& VCO regulator) design at low kHz frequency offsets.

We did not benchmark with ADS or other tools, but hope to benchmark with silicon in the near future!

cheers
aw

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pancho_hideboo

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Re: Augmented Pnoise of Cadence Spectre
Reply #2 - May 12^th, 2009, 6:41am

Thanks for comments

ACWWong wrote on May 12^th, 2009, 5:48am:

We use "Augmented Pnoise" in our last design tape-out,
it gave us more conservative (i.e. higher) estimation of phase noise than vanilla pnoise.
This was especially true in our VCO (& VCO regulator) design at low kHz frequency offsets.

Vanilla Pnoise tends to give phase noise of more than 0dBc for very small offset frequency and not to show f^-3 region in phase noise spectrum plot clearly regardless of phase noise of more than 0dBc.

However according to your comments, "Augmented Pnoise" for your design does give higher phase noise for very small offset frequency than Vanilla Pnoise.

"Augmented Pnoise" doesn't give phase noise of more than 0dBc for very small offset frequency, although it gives higher phase noise than Vanilla Pnoise ?
It does result in a Lorentzian plot truely ?
If so, "Augmented Pnoise" has to suppress f^-3 region in phase noise.

ACWWong wrote on May 12^th, 2009, 5:48am:

We did not benchmark with ADS or other tools, but hope to benchmark with silicon in the near future!

I'm looking forward to your report.

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« Last Edit: May 12^th, 2009, 8:15pm by pancho_hideboo »

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rfmems Senior Member Offline Posts: 121	Re: Augmented Pnoise of Cadence Spectre Reply #3 - May 12^th, 2009, 8:47am I thought augmented pnoise should give less noise compared to the old pnoise simulation for large rc. And it should give a lorentzian plot. BTW, why it is called vanilla pnoise?
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pancho_hideboo

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Re: Augmented Pnoise of Cadence Spectre
Reply #4 - May 12^th, 2009, 9:08am

rfmems wrote on May 12^th, 2009, 8:47am:

I thought augmented pnoise should give less noise compared to the old pnoise simulation for large rc.
And it should give a lorentzian plot.

What do you mean by "rc" ?
Expression of "old pnoise" is not proper, it should be "conventional" or "normal" Pnoise.

rfmems wrote on May 12^th, 2009, 8:47am:

BTW, why it is called vanilla pnoise?

It means "conventional" or "normal" Pnoise.

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rfmems Senior Member Offline Posts: 121	Re: Augmented Pnoise of Cadence Spectre Reply #5 - May 12^th, 2009, 9:10am rc means RC time constant.
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rfmems Senior Member Offline Posts: 121	Re: Augmented Pnoise of Cadence Spectre Reply #6 - May 12^th, 2009, 9:12am pancho_hideboo wrote on May 12^th, 2009, 9:08am: rfmems wrote on May 12^th, 2009, 8:47am: BTW, why it is called vanilla pnoise? It means "conventional" or "normal" Pnoise. Well, it seems that this forum improved my English as well.
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rfmems

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Re: Augmented Pnoise of Cadence Spectre
Reply #7 - May 12^th, 2009, 9:22am

pancho_hideboo wrote on May 12^th, 2009, 9:08am:

Expression of "old pnoise" is not proper, it should be "conventional" or "normal" Pnoise.

Hi pancho_hideboo,

I think expression of "normal" is also not proper, because I won't call augumented pnoise abnormal.

Anyway, it seems to me that we both used improper English more or less. But we understood each other perfectly. Surprise!

have fun
rfmems

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oermens

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Re: Augmented Pnoise of Cadence Spectre
Reply #8 - May 12^th, 2009, 11:48am

rfmems wrote on May 12^th, 2009, 9:22am:

pancho_hideboo wrote on May 12^th, 2009, 9:08am:

Expression of "old pnoise" is not proper, it should be "conventional" or "normal" Pnoise.

Hi pancho_hideboo,

I think expression of "normal" is also not proper, because I won't call augumented pnoise abnormal.

Anyway, it seems to me that we both used improper English more or less. But we understood each other perfectly. Surprise!

have fun
rfmems

I think saying just vanilla is short for plain vanilla, like the ice cream flavour - something which is as simple and basic as you can get, no bells and whistles.

Quote:

A major use of vanilla is in flavoring ice cream. The most common flavor of ice cream is vanilla, and thus most people consider it to be the "default" flavor. By analogy, the term "vanilla" is sometimes used as a synonym for "plain".

http://en.wikipedia.org/wiki/Vanilla#Usage 8-)

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pancho_hideboo

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Re: Augmented Pnoise of Cadence Spectre
Reply #9 - May 12^th, 2009, 8:26pm

oermens wrote on May 12^th, 2009, 11:48am:

I think saying just vanilla is short for plain vanilla, like the ice cream flavour - something which is as simple and basic as you can get, no bells and whistles.

Anyone can infer such a meaning of "Vanilla" easily.

rfmems wrote on May 12^th, 2009, 9:22am:

I think expression of "normal" is also not proper, because I won't call augumented pnoise abnormal.

If I see a dictionary, an antonym of "normal" is surely "abnormal".

However an antonym of "normal" is "special" or "enhanced" or "extented" for me.
It is not "abnormal" for me.
As another expression, I choose "Ordinary Pnoise".

"Vanilla Pnoise" is a expression which was introduced by ACWWong not me.
Should I use expessions such as "Chocolate Pnoise" or "Strawberry Pnoise" for expressing "Augmented Pnoise" ?

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pancho_hideboo

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Re: Augmented Pnoise of Cadence Spectre
Reply #10 - May 12^th, 2009, 8:28pm

"Augmented Pnoise" of Cadence Spectre reminds me of "FM Noise analysis ability in phase noise evaluation of Agilent ADSsim which is based on DC operation points and not implemented in current ADSsim".
See pp.143-146 of http://cp.literature.agilent.com/litweb/pdf/ads2003c/pdf/cktsimhb.pdf
This "phase noise from frequency sensitivity analysis" was removed since ADS2004A.

If there is no 1/f noise parameter in model parameters of MOS or BJT,
there is no f^-3 region(Flicker FM Noise, -9dB/oct=-30dB/dec) in phase noise.
In this case, phase noise is naturally a Lorentzian plot.

But if there is 1/f noise parameter in model parameters, f^-3 region appears in phase noise.
In this case, phase noise is not a Lorentzian plot.

"FM Noise analysis ability in phase noise evaluation of Agilent ADSsim" gave this f^-3 region clearly.

Does "Augmented Pnoise of Cadence Spectre" underestimate or overestimate this f^-3 region ?
If "Augmented Pnoise of Cadence Spectre" claims to give a Lorentzian phase noise plot, it must give underestimated phase noise for f^-3 region.

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« Last Edit: May 13^th, 2009, 7:01am by pancho_hideboo »

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rfmems

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Re: Augmented Pnoise of Cadence Spectre
Reply #11 - May 13^th, 2009, 2:58am

pancho_hideboo wrote on May 12^th, 2009, 6:41am:

Vanilla Pnoise tends to give phase noise of more than 0dBc for very small offset frequency and not to show f^-3 region in phase noise spectrum plot clearly regardless of phase noise of more than 0dBc.

Conventional pnoise/hbnoise shows clearly f^-3 region in phase noise, which gets non-physical when the offset are close to and below the line width frequency. Phase noise above 0dBc/Hz can only be observed at offset frequency below line width.

pancho_hideboo wrote on May 12^th, 2009, 6:41am:

However according to your comments, "Augmented Pnoise" for your design does give higher phase noise for very small offset frequency than Vanilla Pnoise.

According to my simulation, using hb/hbnoise for LC oscillators, the phase noise gets smaller for small offset (close and below line width) when augmented hbnoise is chosen. And phase noise clearly shows a Lorentzian plot.

However if shooting pss/pnoise is used, I still see above 0dBc/Hz phase noise and a non-Lorentzian plot. So I believe the augmented pnoise simulation is not working properly.

I heard that augmented pnoise is not a completed work and cadence is still releasing enhancemented versions. So the accuracy of simulation heavily depends on the MMSIM version you are using.

pancho_hideboo wrote on May 12^th, 2009, 6:41am:

If so, "Augmented Pnoise" has to suppress f^-3 region in phase noise.

I believe that is wrong, augmented hb/hbnoise simulation shows both a lorentzian plot and f^(-3) region.

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pancho_hideboo

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Re: Augmented Pnoise of Cadence Spectre
Reply #12 - May 13^th, 2009, 4:00am

rfmems wrote on May 13^th, 2009, 2:58am:

Conventional pnoise/hbnoise shows clearly f^-3 region in phase noise

No.
If we compare phase noise results of f^-3 region between Agilent ADSsim and Cadence Spectre Conventional Pnoise, Agilent ADSsim often gives more matched results with actual measurement data.

rfmems wrote on May 13^th, 2009, 2:58am:

pancho_hideboo wrote on May 12^th, 2009, 6:41am:

However according to your comments, "Augmented Pnoise" for your design does give higher phase noise for very small offset frequency than Vanilla Pnoise.

According to my simulation, using hb/hbnoise for LC oscillators,
the phase noise gets smaller for small offset (close and below line width) when augmented hbnoise is chosen.
And phase noise clearly shows a Lorentzian plot.

Your tendency about "Augmented Pnoise" is different from one of ACWWong.

rfmems wrote on May 13^th, 2009, 2:58am:

However if shooting pss/pnoise is used, I still see above 0dBc/Hz phase noise and a non-Lorentzian plot.

"Augmented Pnoise" has been already implemented in Shooting-PSS/Pnoise ?
I think it is still only for HB-PSS/Pnoise.

rfmems wrote on May 13^th, 2009, 2:58am:

I heard that augmented pnoise is not a completed work and cadence is still releasing enhancemented versions.

Before completing or improving, this "Augmented" option in Pnoise might be forgotten as same as many imcomplete options of Cadence SpectreRF.

rfmems wrote on May 13^th, 2009, 2:58am:

pancho_hideboo wrote on May 12^th, 2009, 6:41am:

If so, "Augmented Pnoise" has to suppress f^-3 region in phase noise.

I believe that is wrong, augmented hb/hbnoise simulation shows both a lorentzian plot and f^(-3) region.

Based on "Lorentzian Spectrum", the spectrum is flat up to the 3dB-linewidth point, and roll-off at 20dB/decade thereafter.

I don't know definition of "Lorentzian Spectrum" which include f^-3 region.

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« Last Edit: May 13^th, 2009, 7:45am by pancho_hideboo »

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rfmems

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Re: Augmented Pnoise of Cadence Spectre
Reply #13 - May 13^th, 2009, 6:26am

pancho_hideboo wrote on May 13^th, 2009, 4:00am:

Based on "Lorentzian Spectrum", the spectrum is flat up to the 3dB-linewidth point, and roll-off at 20dB/decade thereafter.

The full spectrum of the oscillator has the shape of a Lorentzian around the carrier, and
away from the carrier, the white-noise sources contribute a term
that has a f^-2 frequency dependence, and the flicker noise
sources contribute terms that have a f^-3 frequency dependence.

The complete phase noise spectrum is not Lorentzian, but the part around the carrier is.

That is what I meant by
rfmems wrote on May 13^th, 2009, 2:58am:

augmented hb/hbnoise simulation shows both a lorentzian plot and f^(-3) region.

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rfmems

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Re: Augmented Pnoise of Cadence Spectre
Reply #14 - May 13^th, 2009, 6:41am

pancho_hideboo wrote on May 13^th, 2009, 4:00am:

Your tendency about "Augmented Pnoise" is different from one of ACWWong.

Whether we were talking about the same thing depends on if ACWong compared his hb/hbnoise "augmented" to conventional hb/hbnoise or shooting pss/pnoise.

BTW, I got the feeling that you have strong faith in ADSsim. People with different experiences have different opnions. I am happy with Spectre so far.

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