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Measurements >> Phase Noise and Jitter Measurements >> VCO OCEAN SCRIPT CONVERGENCE PROBLEM
https://designers-guide.org/forum/YaBB.pl?num=1128291821

Message started by jm1974 on Oct 2^nd, 2005, 3:23pm

Title: VCO OCEAN SCRIPT CONVERGENCE PROBLEM
Post by jm1974 on Oct 2^nd, 2005, 3:23pm

I am doing corners analysis using an ocean script I created for VCO.
I'm running the following pss and pnoise analysis and calculating the noise using an expression.

analysis('pnoise ?sweeptype "relative" ?relharmnum "1" ?start "1k"
?stop "20M" ?maxsideband "10" ?p "/out" ?n "/gnd"
?oprobe "" ?iprobe "" ?refsideband "" )
analysis('pss ?fund "2G" ?harms "2" ?errpreset "conservative"
?tstab "171n" ?saveinit "yes" ?p "/out" ?n "/gnd"
?method "gear2only" ?tstabmethod "gear2only" ?tstart "40n" )

run()
;*******************************************************************************
; Output results
;*******************************************************************************
;*******************************************************************************
; Run analyses
;*******************************************************************************

pn10k = value((-dB20(ymax(mag((v "/out" ?result "pss-fd.pss" ?resultsDir "/proj/work_libs/jm/cds/simulation/vco_sim1/spectre/schematic")))) + dB20(getData("/out" ?result "pnoise-pnoise" ?resultsDir "/proj/work_libs/jm/cds/simulation/vco_sim1/spectre/schematic"))
+ 3) 10000)
printf( "%6.2e \n" pn10k)

Half way through the 400 iterations my script goes through a convergence problem. PSS does not converge. This causes evaluation of expression to fail ( cannot evaluate ymax of nil) and the script stops running and exit the iteration. But what I want to do is ignore this one corner and move to the next iteration. I will address the bad convergence corners later. I can't find a way to work around this and I was hoping you all might be of help.

Thanks
JM

Title: Re: VCO OCEAN SCRIPT CONVERGENCE PROBLEM
Post by Andrew Beckett on Oct 4^th, 2005, 9:56pm

Surround the processing with some conditional statements which check for results being present. For example:

Code:

when(mysig=v("/out" ?result "pss-fd.pss" ?resultsDir "/proj/work_libs/jm/cds/simulation/vco_sim1/spectre/schematic")
pn10k = value((-dB20(ymax(mag(mysig)) ...
printf( "%6.2e \n" pn10k)
) ; when

If the v("/out") returns nil, it won't execute the code which fails due to invalid values.

Regards,

Andrew.