[SI-LIST] Re: 50 ohms cable model

Hello,
   I agree with Steve W comments.  I have seen this way back when I modeled 
t-lines as LC networks.  The issue is that the simulator is seeing a large 
inductance for the rising edge of your pulse.  I recommend you either, use 
the lossless T-line, re-build you model so that one LC segment is no more 
then 10%of a rising edge, or slow the rising edge down to be 10 times the 
LC time constant of the T-line segment.  You might want to look at Ron 
Poon's book.  I believe it shows this example fairly well.
Regards
-Ed








At 10:26 AM 11/23/2005 -0800, Truong, Gerald (Space Technology) wrote:
>Hello SIGurus,
>I modeled a 50 ohms cable using the data in cable's datasheet. The
>equivalent distributed L and C yield 50 ohms but when I run the
>simulation with a buffer that has a 50 ohms source impedance, the
>results exhibit overshoot. When I run the simulation with the buffer
>connected to a 50 ohms trace, the results yield a waveform with no
>overshoot, as I would expect in a perfectly match transmission line
>environment.
>
>Does anyone have an explanation for why the 50 ohms cable induces
>overshoot?
>
>Thank you for your time.
>
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