Re: [SI-LIST] : Simulations

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From: Scott McMorrow ([email protected])
Date: Fri Jan 14 2000 - 11:55:36 PST


Doug,

I always start with basic theoretical structures for simulator testing.
You'd be surprised just how many simulators and algorithms have
dc offset errors when simulating lines with losses. Like you, I can
calculate the proper results by hand.

I find that often errors are not so much in the simulator as they
are in the method of parameter extraction and approximation of
elements in the system.

Comparing simulator results to measured data is not a very
accurate science unless you have previously characterized the
simulator in a theoretical environment and therefore trust it's
basic correctness. Then, the next layer of the puzzle becomes
verifying the parameter extractor and trace modeler, which is
a bit tricky ... especially if you are looking for timing accuracy
of less than 10 ps. I have found parameter extraction and trace
modeling algorithms which create networks which have
cumulative error across multiple cascaded trace segments.
I have also seen simulation algorithms which show cumulative
error when the number of individual trace segments is large, as
is the case with most signal traces on PCB's.

Then comes the case of validating a know theoretically good
simulator, parameter extractor, and trace modeler to reality.
Yuck! Of course, first one must verify all parameters in the
target real design, which is not a simple task. But that is another
long story best left for other days.

regards,

scott

--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com

Doug Smith wrote:

> Hi All, > > I am interested in ways that people use to verify simulation results, > that is to check that the results reflect reality. In the past, I have > built up similar, but simple enough to calculate or build, structures > and made sure the simulator agreed with what I measured/calculated by > hand. Sometimes, I have also looked at the convergence history of some > of the requested output. Occassionally, a simulator would produce an > answer that was not properly converged. Seems like is a good idea to > know beforehand the general nature of the answer so you know when the > simulator is not working as expected. > > What other techniques have been used? Any war stories out there? > > Doug > > -- > ---------------------------------------------------------- > ___ _ Doug Smith > \ / ) Manager EMC Development & Test > ========= Auspex Systems > _ / \ / \ _ 2300 Central Expressway > / /\ \ ] / /\ \ Santa Clara, CA 95050-2516 > | q-----( ) | o | Phone/FAX: 408-566-2157/2020 > \ _ / ] \ _ / Email: [email protected] > ---------------------------------------------------------- > > **** To unsubscribe from si-list: send e-mail to [email protected]. In the BODY of message put: UNSUBSCRIBE si-list, for more help, put HELP. > si-list archives are accessible at http://www.qsl.net/wb6tpu > ****

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