alireza wrote on Nov 28th, 2009, 6:56pm:Therefore, the difference in the input noise spectrums was because of different definitions of gain.
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 28th, 2009, 6:56pm:Does it mean that in reality the input-referred noise of a SC integrator (caused by white noise sources) is "not completely white"?
alireza wrote on Nov 28th, 2009, 6:56pm:Because in that case, a white noise assumption seems to be totally inadequate. (and/or unrealistic.)
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 28th, 2009, 6:56pm:for the purpose of simulating discrete-time (SC) circuits
would you recommend using pnoise (sources) (+ SH blocks at the input and the output of the circuit)
instead of pnoise (time-domain)?
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#3alireza wrote on Nov 28th, 2009, 6:56pm:In the paper: "Simulating SC Filters with SpectreRF", it mentions td noise analysis was built for this purpose.
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 28th, 2009, 6:56pm:but it seems that the pnoise (sources) is more accurate?
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#23The 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