[SI-LIST] Re: lumped model vs distributed model
- From: Steve Corey <steve@xxxxxxxxxxxxxx>
- To: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx>
- Date: Fri, 30 Nov 2001 13:40:45 -0800
Hi Jason -- the primary difference between lumped and distributed models is
not accuracy, but simulation speed. We create both lumped and distributed
models that accurately characterize transmission lines (dielectric loss and
skin effect included) all the way to the 35ps risetime of a TDR. If a
transmission line is very long compared to the risetime with which you are
driving it, a distributed model will be noticeably faster than a lumped
model, and this is its main advantage.
If you are using a lumped model with frequency-independent RLC parameters,
which many lumped models have, then you won't effectively model skin effect
or dielectric loss. These can become important as low as the 100 MHz range,
but how important they are really depends on your application. However, it
should be noted that not every distributed model handles frequency-dependent
effects, either.
If you really want to know what you might be missing in your simulations,
your best bet is to measure with a TDR and compare the measurements against
your simulation.
-- Steve
-------------------------------------------
Steven D. Corey, Ph.D.
Time Domain Analysis Systems, Inc.
"The Interconnect Modeling Company."
http://www.tdasystems.com
email: steve@xxxxxxxxxxxxxx
phone: (503) 246-2272
fax: (503) 246-2282
-------------------------------------------
Jason D Leung wrote:
> Hi everyone:
> For transmission line we can always use a lumped R,L,C model to
> represent a simple transmission line, or we can use a distributed model
> .(I know that the distributed model is more accurate and for high freq
> application we should use this model)
> But my question is : what is the main difference between the lumped
> model and distributed model?
> If we are just using the lumped model for our SI simulation, what are we
> going to miss ?
> looking forward for your insight
> thanks
> Regards
> Jason Leung
>
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