alireza wrote on Nov 24^th, 2009, 10:09pm:
Not correct. You have to integrate from 0 to infinity ideally.

However from practical point of view,
an integration from 0 to fs at least might be enough useful.
This range is mainlobe of output noise spectrum.

alireza wrote on Nov 24^th, 2009, 10:09pm:
I think it is due to aliasing.

alireza wrote on Nov 24^th, 2009, 10:09pm:
Again, No.

alireza wrote on Nov 27^th, 2009, 8:43pm:
Attached figures are input and output noise spectrum comparison between type=timedomain and type=sources.
As you can see, I can get very reasonable results both for input and output noise spectrum.

Show me your definition of input noise in pnoise(type=timedomain) as OCEAN Script.

My definitios are followings:

For type=sources Code:

in1_dBV = dB20( getData("out" ?result "pnoise-pnoise") / harmonic( v("/sh" ?result "pac-pac") '(0) ) )
in2_dBV = dB20( getData("in" ?result "pnoise-pnoise") )
out_dBV = dB20( getData("out" ?result "pnoise-pnoise") ) 

For type=timedomain Code:

in_dBV = dB20( getData("out" ?result "pnoise-timedomain.pnoise") / harmonic( v("/sh" ?result "pac-pac") '(0)) ) )
out_dBV = dB20( getData("out" ?result "pnoise-timedomain.pnoise") ) 

Hill around fs/2 in type=sources is due to folding not aliasing.

pancho_hideboo wrote on Nov 22^nd, 2009, 11:07pm:
I can make out the reason why Cadence HB-PSS/PAC can not give reasonable results.

Event-driven constructs such as @(cross) and @(timer) will not be triggered in HB Analysis.
HB Analysis also doesn't support $abstime.

You use "sh" and "nor_gate" Verilog-A modules.

"sh" include @(timer) and $abstime.
"nor_gate" include @(cross).

@(cross) in "nor_gate" is no problem actually.

But @(timer) and $abstime in "sh" are very problematic for HB Analaysis.

In Agilent RFDE(ADSsim), Sample&Hold component which is effective even in HB Analysis is provided.
http://edocs.soco.agilent.com/display/ads2009/SampleHoldSML+%28Sample+Hold%29

Also there is more sophisticated switch component in Agilent RFDE(ADSsim) more than Cadence Spectre "relay" component.
http://edocs.soco.agilent.com/display/ads2009/SwitchV+%28Voltage+Controlled+Swit...

And I can build various custom components which are effective in HB Analysis by using FDD(Frequency-Domain Defined Devices)
http://edocs.soco.agilent.com/display/ads2009/Custom+Modeling+with+Frequency-Dom...

I can use these components in Cadence Spectre Syntax netlists when I use RFDE(ADSsim) as simulator.

alireza wrote on Nov 28^th, 2009, 8:04am:
What do you mean ?

I showed spectrums at 0ns, 5ns, 10n, 20n, 25n, 30n.
There is almost no difference between them.
However If I choose time point at edge of clock signal, spectrum could be more large.

alireza wrote on Nov 28^th, 2009, 8:04am:
You wrote your output noise spectrums are different by 4dB between tdnoise and pnoise(sources). But your input noise spectrums are same between them.
alireza wrote on Nov 22^nd, 2009, 10:04pm:
alireza wrote on Nov 19^th, 2009, 6:26pm:

I think your definition of input noise in tdnoise is wrong.

Again show me your definition of input noise in pnoise(type=timedomain) as OCEAN Script.

alireza wrote on Nov 28^th, 2009, 8:04am:
Folding in pnoise(sources) is not issue at all.
Folding in pnoise(sources) is very actual.

You must not confuse folding with aliasing.

alireza wrote on Nov 28^th, 2009, 8:04am:
Still you can't understand correctly.

The integrated input-referred noise power in pnoise(type=sources) is very correct and the simulation is very useful.

Are you very familiar with IIR digital filter which is approximation as continuous time analog filter ?
Frequency definition is (-infinity, +infinity) for continuous time analog filter.
However this range is mapped to (-fs/2, +fs/2) for approximated IIR filter.
Frequency range of tdnoise is a little similar to this.

alireza wrote on Nov 28^th, 2009, 8:43am:
No. you are misunderstanding.

Basically I don't use Direct Plot Form in Cadence ADE where there are many bugs and definition of equations are very suspicious especially for RF applications.
http://www.designers-guide.org/Forum/YaBB.pl?num=1237656418/1#1

All noise spectrums are dBV/Hz unit. Again see OCEAN definition of these.
Only Yellow bold line is pnoise(sources). Other six lines are all tdnoise results.
See Yellow bold line in output noise spectrum. You can see only this line is from 0 to 50MHz.

We can't find out any remarkable difference between these six tdnoise input noise results.
Input noise results of tdnoise are all higher than pnoise(sources) by 4dB at fs/2.

pancho_hideboo wrote on Nov 28^th, 2009, 8:10am:
This ignores folding effects.

Again folding is a reality.
http://www.designers-guide.org/Forum/YaBB.pl?num=1258339986/19#19

Output noise spectrum is a result of contribution from all sidebands, that is, multiple foldings.
While VGain of PAC considers only zero sideband.

alireza wrote on Nov 28^th, 2009, 6:56pm:
As I expected, you use different definition of input noise between pnoise(sources) and pnoise(timedomain).

You must not use Direct Plot Form in Cadence ADE blindly.

alireza wrote on Nov 28^th, 2009, 6:56pm:
alireza wrote on Nov 28^th, 2009, 6:56pm:
Pink noise is a result of correlation in time domain.

There is a correlation in time domain for SC integrator naturally since you use two Sample&Hold Circuits.

Note : Correlation of noises in frequency domain results in shaping of noise in time domain.

alireza wrote on Nov 28^th, 2009, 6:56pm:
Unless your interest is a behavior of noise spectrum at clock edge, I don't recommend you to use pnoise(timedomain).

As you know, tdnoise takes very very much time in completion.
But even if you observe spectrum at clock edge by using tdnoise, you can never get any novel or valuable information so much.

Also see http://www.designers-guide.org/Forum/YaBB.pl?num=1220976977/3#3

alireza wrote on Nov 28^th, 2009, 6:56pm:
This is no more than an advertisement of very specific vendor's EDA Tool.

EDA Tool Play is no more than Tool Play.
There is nothing superior to the actual measurement using actual instruments.

alireza wrote on Nov 28^th, 2009, 6:56pm:
Accuracies of them are same.
Again see http://www.designers-guide.org/Forum/YaBB.pl?num=1242797715/1#1

"sources" and "timedomain" are no more than small signal analysis in frequency domain.
"sources" give you Time_Averaged_Noise_Power_Density(freq),
while "timedomain" give you Ensemble_Averaged_Noise_Power_Density(time,freq).
But meaning or interpretation of frequency spectrum is different between these two.
Again see my last comment in http://www.designers-guide.org/Forum/YaBB.pl?num=1258339986/23#23


The followings are general notes.

  - Use correct terminologies.
  - Warnigns are different from Errors.
  - ADS is not name of simulator.
  - There is no tool which name is Cadence.
  - Don't use Direct Plot of Cadence ADE blindly without knowing definition.
  - All gains in Direct Plot of Cadence ADE are "right", "true" and "practical" voltage gain.
  - MATLAB are different from Simulink.
  - Learn measurements using actual instruments. Not "EDA Tool Play

Hi,

I just have a couple of more questions regarding PSS/pnoise simulations. I am right now using the pnoise(type=sources) to find the input referred noise power of the SC integrator. I am using the integrator in open loop mode (without the S/H block feeding back to the input, and I don't have any stability issues, due to finite opamp gain.)
My circuit parameters are as follows: gm_opamp=1, Rout_opamp=1M, Ron_switch=600ohm, Cs=CI=1pF, R_opamp=0 (to model opamp noise) (please see the attached schematic.)

I am looking at the input-referred noise spectrum, based on your OCEAN script:  
(mag(getData("in" ?result "pnoise-pnoise"))**2)

The simulation results are fine at low frequencies (below fs). However I do have an spike occurring at fs=25MHz. (please see the attached curves.)

If I want to find the total integrated input-referred noise power, I should integrate the spectrum from 0 to inf, which of course includes the singular point.

Now, I am not sure, what to do with the singular point at 25MHz? Should this happen in reality? or is it again an artifact? (It only occurs at 25MHZ but not other harmonics!) (My PSS analysis engine is Shooting, as HB does not give reasonable results with the hidden-states free SH block I am using)

Even if I ignore this spike, the input noise spectrum does not fall off at high frequencies, so essentially if I integrate it, it will yield a noise power which is much larger than expected.

The above curve is for the noise density referred back to the input of the circuit (node:Inp), where PAC source is connected. This corresponds to the "input" of the "input SH". However, if I refer the noise back to the "output" of the "input SH" (node:In_sh), I get a different curve (second curve in the attached plot) If I integrate this curve from 0 to inf, I do not have any spikes and almost get the right input referred noise power. (10.54nV^2 for Cs=1pF). However I am not sure whether this node is the one I should refer back the noise to.

Thanks a lot,

Regards,
Alireza