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Related to "How to specify phase noise as an instance parameter in spectre sources (e.g. vsource, isource, port)"

mzn ehv

Hello,

I am trying to specify the phase noise as an instance parameter of spectre sources such as port and vsource as mentioned in the article  https://support.cadence.com/apex/ArticleAttachmentPortal?id=a1Od0000000tiraEAA&pageName=ArticleContent

When I create a test bench containing one port without specification of phase noise and other port with specification of phase noise, I do not see any difference in their time domain waveforms. So, it looks like it’s not incorporating the phase noise as required.

I am using cadence-icadvm-/20.10.340 and spectre 23.10.538.isr10. Attached is the netlist of the testbench.

// Generated for: spectre
// Design library name: AAA_AA
// Design cell name: pn_modelling_tb
// Design view name: schematic
simulator lang=spectre
global 0
parameters fin=20M tstop=1000/fin

// Cell name: pn_modelling_tb
// View name: schematic
R0 (clk 0) resistor r=50
R14 (ideal_clk 0) resistor r=50
PORT1 (clk 0) port r=50 type=sine freq=fin ampl=1 isnoisy=yes \
noisetype=ssbphasenoise noisevec=[ 1K -100 10K -100 100K -100 1M \
-100 10M -100 ]
PORT0 (ideal_clk 0) port r=50 type=sine freq=fin ampl=1
simulatorOptions options psfversion="1.4.0" reltol=1e-3 vabstol=1e-6 \
iabstol=1e-12 temp=27 tnom=27 scalem=1.0 scale=1.0 gmin=1e-12 rforce=1 \
maxnotes=5 maxwarns=5 digits=5 cols=80 pivrel=1e-3 \
sensfile="../psf/sens.output" checklimitdest=psf
tran tran stop=tstop write="spectre.ic" writefinal="spectre.fc" \
annotate=status maxiters=5
finalTimeOP info what=oppoint where=rawfile
modelParameter info what=models where=rawfile
element info what=inst where=rawfile
outputParameter info what=output where=rawfile
designParamVals info what=parameters where=rawfile
primitives info what=primitives where=rawfile
subckts info what=subckts where=rawfile
save ideal_clk clk
saveOptions options save=allpub

Is there anything which I am missing here?

Thanks

Parents
  • Andrew Beckett

    You're not running transient noise (or a pnoise/hbnoise analysis), so you won't see any noise generated by this source.

    With noisefmax=fin*10 (say) on the transient analysis, the noise is generated - although you're unlikely to see it as it's small - in reality you'd have to do an DFT of the results, in which case you'd want to set strobeperiod and ensure that the DFT sampling interval coincides with the strobeperiod.

    Of course, if you do this, you'll also get the thermal noise from the resistor and the 50 ohms in the port - and any other devices in the real circuit. Note that the isnoisy=yes on the port is redundant because noise is enabled on sources by default, just doesn't appear in a non-noise-related analysis.

    Andrew

  • mzn ehv
    in reply to Andrew Beckett

    Thank you Andrew for your response.
    When I enable transient noise, I indeed see the difference between noisy and non noisy source. 
    To remove the impact of 50 ohms in the port, I changed the source to vsource keeping all other parameters same. With -100 dBc/Hz phase noise floor and fin = 20 MHz, I expect an rms jitter of 355 ps, but evaluation using calculator function 'rms_jitter' (integrated from 1 to 10M) yields number in the ballpark of 250 ps (with noisefmax swept from fin*5 to fin*20 and 1k-10k fin cycles). Why these two numbers are differing?

Reply
  • mzn ehv
    in reply to Andrew Beckett

    Thank you Andrew for your response.
    When I enable transient noise, I indeed see the difference between noisy and non noisy source. 
    To remove the impact of 50 ohms in the port, I changed the source to vsource keeping all other parameters same. With -100 dBc/Hz phase noise floor and fin = 20 MHz, I expect an rms jitter of 355 ps, but evaluation using calculator function 'rms_jitter' (integrated from 1 to 10M) yields number in the ballpark of 250 ps (with noisefmax swept from fin*5 to fin*20 and 1k-10k fin cycles). Why these two numbers are differing?

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