Hello Mitch, If the crosstalk model is based upon cap coupling the output of
a series L and shunt C voltage divider, then crosstalk will increase with
rise time up to a point and then start decreasing as the equivalent coupling
cap between traces approaches an open circuit.  I can't be sure without
knowing what the Automata model is, but I think this explanation comes
pretty close to whats going on.  The tip-offs are negative crosstalk values
from Automatas calculator, and from the output calculation of a series L
shunt C divider above resonance.  The negative values only mean that the
crosstalk signal is 180 degrees out of phase with the source.  Hope this
helps!  John.

  

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HELP!  The engineer I work with has some issues I am hoping someone can
       enlighten me on.

> I have been using Automata in the past but stopped becuase something
> doesn't seem right about the results it gives.  Maybe I am wrong but 
> shouldn't the crosstalk increase when the signal rise time increases 
> if all else is held constant?

> When I use the Automata Engineering Tools for doing lateral crosstalk 
> calculations the slower the rise time the larger the crosstalk result 
> becomes.  Just doesn't seem right to me.  Again, maybe I'm wrong!

Here is two calculations from Automata:

Automata's Lateral Crosstalk Modeling

You submitted the following name/value pairs:

     Er = 4.3 
     h1 = 8 
     h2 = 8 
     t = 1 Oz 
     w = 6 
     sx = 6 
     length = 2 
**** risetime = 1.9 **** 

The crosstalk = 24.9 mv/v
                ----

Automata's Lateral Crosstalk Modeling

You submitted the following name/value pairs:

     Er = 4.3 
     h1 = 8 
     h2 = 8 
     t = 1 Oz 
     w = 6 
     sx = 6 
     length = 2 
**** risetime = 3.1 ****

The crosstalk = 31.9 mv/v
                ----

Does this seem correct to you?

Thanks in advance for any help.



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