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Other CAD Tools >> Physical Verification, Extraction and Analysis >> Assura Extraction problem in IBM 7RF
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Message started by vipul on Oct 11^th, 2005, 2:56am

Title: Assura Extraction problem in IBM 7RF
Post by vipul on Oct 11^th, 2005, 2:56am

Hi,

I am using the IBM 7RF kit to design circuits for frequencies above 10GHz. The parasitic extraction using Assura seems to be inaccurate for parasitic resistances. Sometimes, it shows resistances as big as several kil-ohms, while Diva shows only a few ohms.
Has anyone had a similar problem? Is it a bug?
I am using IC5141 and Assura 314 on a Linux machine.
Is Diva reliable? (e.g how much deviation can I expect in measurements)
I can provide more details of what procedure I am following exacly, if that helps.

Thanks
Vipul

Title: Re: Assura Extraction problem in IBM 7RF
Post by Andrew Beckett on Oct 12^th, 2005, 1:45pm

Note that Assura tends to lump together resistors far more than Diva does - Diva often leaves lots of small resistors in a complex mesh, because it does only limited reduction (and even then, it will only reduce if it can make the network smaller with the same overall resistance, and it will only combine resistors which came from the same layer - if my memory is correct).

So you may not be comparing like with like?

Any concerns you have over accuracy of the extraction rules should go to IBM, I'd have thought.

Regards,

Andrew.

Title: Re: Assura Extraction problem in IBM 7RF
Post by vipul on Oct 14^th, 2005, 12:57am

I found the answer on the Cadence Sourcelink website. Assura does some Wye to Dlta transformations on the resistive network that it extracts, and in turn comes up with large values. This does not affect the electrical equivalence of the extracted view; just that what it back-annotates on the schematic gives the user a wrong impression. A work-around is to specify a larger value for the minR parameter.
I have some more problems that I am writing in a separate post.

Thanks for your help
Vipul