[SI-LIST] Re: even and odd mode crosstalk consideration

From: yous@xxxxxxxxxxxx
To: bhadhua@xxxxxxxxxxxx
Date: Tue, 26 Oct 2004 11:25:24 -0600
To Dear All members of SI list:

How are you? I expected and waited someone answered this question because I
wanted to know. One thing I can say is that C_even = C11 - Cm & L_odd = L11 -
Lm equations should be correct when geometry has symmetrical shape otherwise
the transformation equations do not work.  What I don't know is that when the
geometry does not have symmetrical shape (so-called c-mode and pi-mode) whether
there is transformation equation or not.

Thank you very much.
Sincerely,
Se-Ho You


---
Hi all,

I am trying to simulate the effect of mutual inductance and mutual
capacitance between a pair of parallel conductors in hspice. I will
describe the two cases that I am trying to do and the results observed.

case1)

When the 2 parallel conductors have the same length, width, thickness and
the overlap length = length of the conductor(s):

                      _____________________________
                      |____________________________|

                      _____________________________
                      |____________________________|

In the above case, when the signal propagates in even mode along both the
conductors, if I use the transformation of L_even = L11 + Lm and
C_even = C11 - Cm on any of the conductors (and neglecting the effect
of the other conductor) then the Voltage vs time curve
at the terminal end of the conductor exactly corresponds to the Voltage vs
time curve obtained without doing the transformation and keeping the
effect of both the conductors in the hspice netlist. Here Lm and Cm
denotes mutual inductance and mutual capacitance respectively.
The same is observed in odd mode by doing the transformation L_odd = L11 -
Lm and C_odd = C11 + Cm. Hence the theory (Stephen Hall) actually holds
during simulation.

case2)

When the 2 parallel conductors have UNEQUAL lengths but same width and
thickness and the OVERLAP LENGTH != length of the conductor(s). Meaning
one conductor is displaced w.r.t the other conductor.

                     ____________________
                     |___________________|

                            _____________________________________
                            |____________________________________|


In this case after finding the Lm and Cm I use the same transformation as
case1 and the same experimentation setup as above, but the V vs time
curve DOES NOT give an exact match for the two experiments in bot even and
odd mode.

Can anyone suggest the reason behind the discrepancy observed in these two
cases? Probably the way Lm is calculated in case 2 is an approximation,
but still I guess the curves should closely follow each other, which is
not happening. It might also happen that the way the transformation needs
to be done in case2 is different from the way I am doing.

Thanks,
Amitava

Amitava Bhaduri
Research Assistant
527 ERC
University of Cincinnati
OH - 45221
ph(lab) : 513-556-3025

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[SI-LIST] Re: even and odd mode crosstalk consideration

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