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pancho_hideboo

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Re: Augmented Pnoise of Cadence Spectre
Reply #15 - May 13^th, 2009, 6:59am

rfmems wrote on May 13^th, 2009, 6:41am:

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.

I'm now planning to move SmartSpiceRF due to cost reduction purpose.

I'm very enhancing in actual measurements maybe than you.
I've always said to people in this forum, You have to learn measurements using actual instruments. Not "EDA Tool Play".

Generally Cadence Tool Players have no experience of actual measurements.

I have Agilent ADSsim, GoldenGate and Cadence SpectreRF.
I've intensively compared simulation data with actual measurement data over long years since Agilent MDS and EEsof Series-IV Libra days when SpectreRF didn't exist.

In my country, Cadence Spectre is not used for RF circuit design mainly.
However only for VCO design, there are many people who are using Cadence Spectre.

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pancho_hideboo

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Re: Augmented Pnoise of Cadence Spectre
Reply #16 - May 13^th, 2009, 7:03am

rfmems wrote on May 13^th, 2009, 6:26am:

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

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

(1) {1/(a²+f_offset²)} * {1+k₁/(b+f_offset)}

(2) {k₁/(a²+f_offset²)} + {k₂/(c³+f_offset³)}

Which is "Lorentzian Power Spectrum" including f^-3 region ?

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« Last Edit: May 13^th, 2009, 10:54am by pancho_hideboo »

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rfmems

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Re: Augmented Pnoise of Cadence Spectre
Reply #17 - May 13^th, 2009, 7:49am

pancho_hideboo wrote on May 13^th, 2009, 6:59am:

I'm enhancing in actual measurements maybe than you.
I've always said to people in this forum, You have to learn measurements using actual instruments. Not "EDA Tool Play".

I am really curious to know what are you based on to make these claims. It may surprise you that I measure my chip myself as well. �

pancho_hideboo wrote on May 13^th, 2009, 6:59am:

Generally Cadence Tool Players have no experience of actual measurements.

I guess lots of people in this forum disagree with you. Actually, I think nowadays most of the industries and academies using spectreRF for analog/rf designs. And most of the designers measure their critical block (if not the whole chip) themselves!

pancho_hideboo wrote on May 13^th, 2009, 6:59am:

I have Agilent ADSsim, GoldenGate and Cadence SpectreRF.
I've intensively compared simulation data with actual measurement data over long years since Agilent MDS and EEsof Series-IV Libra days when SpectreRF didn't exist.

It may surprise you again, I, who is not "enhancing in actual measurements" as you think, also use ADSsim. I said I am happy with Spectre based on my experience of simulation and measurement. Maybe there is some flaw of spectre which I have not discovered yet. But I said "so far"!

I thought you started this topic for discussion, not for confrontation. But I was wrong! You first pulled up my English, then outbursted to "command" me to learn measurement. Come on, this is a forum, not a colosseum!

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rfmems

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Re: Augmented Pnoise of Cadence Spectre
Reply #18 - May 13^th, 2009, 7:54am

pancho_hideboo wrote on May 13^th, 2009, 7:03am:

Which is "Lorentzian Power Spectrum" including f^-3 region ?

I did not say "Lorentzian Power Spectrum" including f^-3 region, I said you can see both Lorentzian and f^-3 region. You understood me wrong.

I would suggest you to read Demir's paper "Phase noise and timing jitter in oscillators with colored-noise sources", if you still find it not crystal clear. (I won't say you don't understand phase noise, that is your style though).

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pancho_hideboo

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Re: Augmented Pnoise of Cadence Spectre
Reply #19 - May 13^th, 2009, 8:06am

rfmems wrote on May 13^th, 2009, 7:49am:

I guess lots of people in this forum disagree with you.
Actually, I think nowadays most of the industries and academies using spectreRF for analog/rf designs.

Are you student or any relation with Cadence ?
I think almost all people except for a few people in this forum are students.

I think you just started to use SpectreRF since two or three years ago.
Did you resolve the following ?
http://www.designers-guide.org/Forum/YaBB.pl?num=1207830622

rfmems wrote on May 13^th, 2009, 7:49am:

And most of the designers measure their critical block (if not the whole chip) themselves!

No.
In old days, designers, especially RF designers were engaged in all tasks.

But nowadays, in most companies, works required for making IC are divided into small tasks.

architectual design, circuit simulation, physical layout design, verification, building block measurements, system evaluation, etc.

Nowadays, designers are engaged in limited tasks in most companies.

Indeed there is no stage for measurement/evaluation and even no feedback path from measurement in design flow of Cadence Top Down Methodology.

rfmems wrote on May 13^th, 2009, 7:54am:

I did not say "Lorentzian Power Spectrum" including f^-3 region, I said you can see both Lorentzian and f^-3 region.

Maybe you just mean some spectrum which have flat top in very small offset region.
Such flat top spectrum is natural result of actual non-linear effects.

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« Last Edit: May 13^th, 2009, 9:15am by pancho_hideboo »

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rfmems

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Re: Augmented Pnoise of Cadence Spectre
Reply #20 - May 13^th, 2009, 9:15am

The conversation is getting harder and harder. Well, I didn't start it, but I will finish it!

If you are doing a PhD, you have to measure your chip all by yourself.
For small startup comapnies, more or less the same situation, you have to verify your own block.
In big companies, I worked in one (top 10 in IC industry), if I designed a critical RF block, I need to measure it for the first fun, see if it works properly, get the right settings and write a measurement proposal for the verification guy. Then he will do the rest, corners, temperatures, and so on.

So you see, almost every RF designer has some measurement experience.

Back to phase noise, I don't think you understand oscillator phase noise thoroughly. Even if flicker noise is presented, you will still have a Lorentzian near the carrier in the form of
c/(pi^2c^2+f^2). You definitely should read that paper!

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pancho_hideboo

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Re: Augmented Pnoise of Cadence Spectre
Reply #21 - May 13^th, 2009, 9:20am

rfmems wrote on May 13^th, 2009, 9:15am:

For small startup comapnies, more or less the same situation, you have to verify your own block.

I also think so.

rfmems wrote on May 13^th, 2009, 9:15am:

So you see, almost every RF designer has some measurement experience.

I don't think so. There are many who have only simulation experiences.

rfmems wrote on May 13^th, 2009, 9:15am:

Even if flicker noise is presented, you will still have a Lorentzian near the carrier in the form of
c/(pi^2c^2+f^2).

Where is f^-3 ?
Do you mean (2) in the following ?

pancho_hideboo wrote on May 13^th, 2009, 7:03am:

(1) {1/(a²+f_offset²)} * {1+k₁/(b+f_offset)}
(2) {k₁/(a²+f_offset²)} + {k₂/(c³+f_offset³)}
Which is "Lorentzian Power Spectrum" including f^-3 region ?

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« Last Edit: May 13^th, 2009, 11:37am by pancho_hideboo »

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rfmems Senior Member Offline Posts: 121	Re: Augmented Pnoise of Cadence Spectre Reply #22 - May 13^th, 2009, 9:35am c/(pi^2c^2+f^2) f close to 0 a/f^2*(b+c/f) f>>0
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pancho_hideboo

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Re: Augmented Pnoise of Cadence Spectre
Reply #23 - May 13^th, 2009, 9:42am

rfmems wrote on May 13^th, 2009, 9:35am:

c/(pi^2c^2+f^2), � f close to 0

I think this is not proper if flicker noise is included.
See pp.12-14 of http://www.designers-guide.org/Analysis/PLLnoise.pdf

rfmems wrote on May 13^th, 2009, 9:35am:

a/f^2*(b+c/f), �f>>0

Correct. This is modified Leeson's Equation.

{1/(a²+f_offset²)} * {1+k₁/(b+f_offset)}
� � or rather
{k₁/(a²+f_offset²)} + {k₂/(c³+f_offset³)}

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« Last Edit: May 13^th, 2009, 11:01am by pancho_hideboo »

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rfmems

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Re: Augmented Pnoise of Cadence Spectre
Reply #24 - May 14^th, 2009, 1:19pm

The modeling of flicker noise differs with foundries. �I have two PDKs at hand, one models the flicker noise with 10dB/dec down to 600uHz, then flats out. while the other keeps the 10dB slop even at 1a Hz. �

Since the augmented hbnoise has no above 0dBc/Hz values, Spectre must have defined a bandwidth below which the flicker noise flats out. That is why simulation shows both Lorentzian (close to carrier) and f^-3 region.

Theoretically, if flicker noise is presented, oscillator noise will be unbounded and not a Lorentzian. But with the flicker noise bandwidth defined, "c/(pi^2c^2+f^2) f close to 0" is valid. If this bandwidth is chosen according to typical measurement (accumulation) time, then the simulation should have a good accordance with measurement. If measure with very long time scale, flicker noise will anyway become indistiguishable from temperature drift.

What is your opinion? pancho_hideboo.

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