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Design >> RF Design >> Transmission line in Cadence
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Message started by mobil on Sep 4^th, 2006, 6:00pm

Title: Transmission line in Cadence
Post by mobil on Sep 4^th, 2006, 6:00pm

Hi All,

Currently, I've concerned the design in GHz level, and have to consider about transmission line effection. We often
use the 'singlewire' component that's from IBM tech. model to simulation in the schematic (as shown in pic.)

But the question is when I'm doing layout, it is hardly to put the 'singlewire' everywhere such as in schematic, because
of the area restrication. So I'm afraid the postlayout simulation won't be very accurate. Does anyone know whether Cadence
can simulate transmission line effection in postlayout simulation to solve the problem above? Thank you.

Title: Re: Transmission line in Cadence
Post by ACWWong on Sep 5^th, 2006, 1:33am

As far as I am aware Cadence post layout extraction (Assura or diva) cannot extract inductance, and hence cannot extract transmission line effects.

Why can't you just shorten the length of the IBM modelled "singlewire" (i guessing this must be the new incarnation of the "indline" model they used to use).

To do things properly, you would need to use another tool to extract the layout tracks in terms of transmission lines.
Anyway what is your frequency and how long are your tracks ? you might invest a lot of work for little actual performance change to your circuit.

Title: Re: Transmission line in Cadence
Post by Andrew Beckett on Sep 5^th, 2006, 7:00am

Actually Assura-RCX has the "PL" option (for extraction of Parasitic Inductance), and the "HF" option which extracts the substrate (so can more accurately model any substrate return path with inductors/transmission lines). These are additional options on top of Assura-RCX. There's a bundle, Assura-RF which includes RCX, PL, HF and FS (the capacitance field solver).

Andrew.

Title: Re: Transmission line in Cadence
Post by mobil on Sep 19^th, 2006, 3:13am

Hi all,

sorry for responsing late, yes, as Andrew said, the best way is to buy licenses of the Cadence for RCX,
but considering I'm in the University, we will only pay for the RCL extraction licenses, hopefully it's useful.

Also, other tools can extract inductor effects I heard is Ansoft Link for Virtuoso Or RFDE.

Thanks.

Title: Re: Transmission line in Cadence
Post by jerrymelb on Dec 17^th, 2006, 2:38pm

Hi, guys

Just wonder how accurate RLCK extraction is?

Can the results be trusted?

Thans!

Title: Re: Transmission line in Cadence
Post by SRF Tech on Dec 18^th, 2006, 7:13am

Jerry,
My experience has been that the extraction tools are only as good as the technology files and process parameters fed to them. Generally they do a good job but I have found that they rely on several parameters of the process technology that sometimes get skimped on or overlooked by the foundary. So as long as you trust that the foundary has modeled/measured many of the process paramters critical for your extraction tool and have not used simple default values, you can expect that the tool will be reasonably accurate.

Generally they do a good job for the RC, its sometimes they miss paramters critical for the K and especially the L.
-SRF