[SI-LIST] Re: lumped model vs distributed model

  • From: "Ozgur Misman" <omism@xxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Fri, 30 Nov 2001 17:16:07 -0700


Also,
In addition to the experiment  Murad is suggesting  you could do the same
simulation in frequency domain. Construct an equivalent circuit both lumped
and  and distributed and  do S-parameter simulation. If your simulation
frequency band is wide  enough  you will see that your lumped model will
give you a  low-pass filter response that is artificial.( Just Plot the
insertion loss (dB) vs. frequency)
Play with the number of segments or lower the frequency you will see the
simulation results converge.

This will make it clearer what people mean by "not enough bandwith". Also
having the results of both frequency domain and time domain simulations
provides good insight on how the same effect reveals itself in two
different approaches.



Bet Regards,




"Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx>@freelists.org on 11/30/2001
03:31:55 PM

Please respond to arpad.muranyi@xxxxxxxxx

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Subject:  [SI-LIST] Re: lumped model vs distributed model



Jason,

I am sure you will get many good theoretical answers
to this question.  However, I would suggest that in
order to get a better understanding, try it out yourself!

If you have a spice simulator, build a network with a single
RLC lump, and compare it with say 10 of them in series, or
100 of them in series (don't forget to divide the individual
element values by the number of lumps, though).  This is not
too hard if you know how to make a subcircuit...  For the
"driver" you can just use a Thevenin circuit, with a Pulse
(or PWL) source where you can vary the edge rate from very
steep (1.0 ps) to less steep (10 ns).  Then run the
simulations and put the waveforms on top of each other.
You should see pretty good differences...

Arpad Muranyi
Intel Corporation
===========================================================

-----Original Message-----
From: Jason D Leung [mailto:jleung@xxxxxxxxxxxxxxx]
Sent: Friday, November 30, 2001 12:19 PM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: lumped model vs distributed model


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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