alireza wrote on Nov 22nd, 2009, 10:04pm:the (upward) spikes in the input-referred noise should occur too.
But those spikes lead to huge input-referred noise if integrated over frequency. true?
I don't think so, as far as your analysis frequency points are enough detailed around these singular points or these singular points are excluded from analysis frequency points.
Note: n*Fund are singular points, but fs/2 is not singular point. fs/2 is nyquist point.
alireza wrote on Nov 22nd, 2009, 10:04pm:OR, do we not care about them?
(Do we integrate the spectrum from 0 to inf or to fs/2?)
The other related question that I had is that do we run the pnoise-sources simulation over a wider freq. range? (than fs/2)
Yes.
0 to inf for "Pnoise(sources)".
0 to fs/2 for "Pnoise(timedomain)".
Again see
http://www.designers-guide.org/Forum/YaBB.pl?num=1059089369/6#6alireza wrote on Nov 22nd, 2009, 10:04pm:Yes, I had set the harmonics to 300 as well.
I don't know why Cadence HB-PSS/PAC can not give reasonable results.
Does iteration of HB trial reach to maximum limit without resulting in small ConvNorm ?
Confirm your simulation logfile.
If you have other simulators such as BDA's Analog FastSPICE, Nexxim, Aplac, ADSsim, GoldenGate, eldoRF, HSPICE-RF, SmartSpice-RF, etc, try to use them.
Other simulator also have both Shooting and HB solvers.
About HB solver, other simulator is far robust than Cadence Spectre.
alireza wrote on Nov 22nd, 2009, 10:04pm:I have attached the output spectrum plots both in dB and linear scale.
There is a difference of about 4 dB at fs/2.
(pnoise-td is higher thatthan pnoise-sources)
It is very reasonable.
alireza wrote on Nov 22nd, 2009, 10:04pm:(pnoise-sources is in dBm, therefore the plot shows 34dB difference.)
Why don't you plot them with same units ?
Upload PSF directory data for both "Shooting-PSS/PAC(sources)/Pnoise(timedomain)" and "Shooting-PSS/PAC(sources)/Pnoise(sources)".
Or upload full netlist with model files and Verilog-A modules so that I can run simulation.
alireza wrote on Nov 22nd, 2009, 10:04pm:The PSS analysis was set as Shooting-PSS.. (But as I showed in the last post, when referred back to the input they both show a rise in the noise floor.)
I will check with PSF data you upload.
Again, n*Fund are singular points, but fs/2 is not singular point. fs/2 is nyquist point.