[SI-LIST] Re: Cascading differential 2-Port Networks
- From: "D G" <dgun@xxxxxxxxxx>
- To: si-list@xxxxxxxxxxxxx
- Date: Sat, 23 Nov 2002 03:29:39 +0800
Bob,
The main problem is that the transformation in text books from S-parameters to
T-parameters is defined for 2x2 matrices. I don't know what the transformation
is for a 4x4 matrix, but I'm sure it can be done. Assuming you find out how to
do it, then just use mixed-mode like you would a standard S-parameter block,
except now it is a 4x4 matrix instead of 2x2. Since the mixed-mode and 4-port
S-parameters are related by a simple linear transformation, all the math
carries over.
Start with the mixed-mode S-matrix, convert to T-parameters, multiply the
matrices, and convert back to S-matrix. You now have a mixed-mode matrix that
reflects two cascaded mixed-mode matrices. Upper-left quadrant is still
differential parameters, Lower-right quadrant is still common-mode parameters,
and the other two quadrants are still mode-conversion parameters.
Again, this assumes that a transformation from 4x4 S-parameters to 4x4
T-parameters can be computed.
A good technical reference is:
Bockelman & Eisenstadt; "Combined Differential and Common-Mode Scattering
Parameters: Theory and Simulation"; IEEE Trans. MTT; July 1995; pp. 1530-1539.
It doesn't talk about T-parameters, but it does talk about how mixed-mode
S-parameters can be treated just like any other 4x4 s-parameter matrix (as long
as you interpret it correctly as I stated above).
From: "Bob Welte" <welte@xxxxxxxxxx>
>
> Hello to All
> I have run into an interesting problem.
> I am trying to put together a simple modeling environment of our 2.5Gb/s
> high speed digital channel using S-parameters. Because it is a
> differential environment, I will be using mixed-mode S-parameters. While I
> understand the concept of converting "S" into "T" parameters and using the
> chain-scattering-matrix to cascade the 2 ports of a channel, I do not know
> what to do when the channel is differential, and you begin with mixed-mode
> S-parameters.
> Can anyone offer a reference, or perhaps share some knowledge?
>
> Bob Welte
> IBM Microelectronics
--
Daniel
ZZZ-dgun-ZZZ-@xxxxxxxxxxxxxxx
(remove the Z-'s to reply--they're what I do when I read spam)
--
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