[SI-LIST] Re: Cascading differential 2-Port Networks
- From: Gary Otonari <garyo@xxxxxxxxxxxx>
- To: dgun@xxxxxxxxxx
- Date: Fri, 22 Nov 2002 18:03:54 -0800
Hi Bob,
Another, although cumbersome alternative would be to use ideal baluns to
convert each differential network into a single-ended 2-port, then cascading
these together as you normally would a single-ended chain. Each individual
differential network would become a 3-element "sub-network" with input and
output baluns surrounding the actual "DUT". It goes without saying that this
is much simpler if your simulator supports an ideal balun.
-- Gary Otonari
GigaTest Labs
D G wrote:
> 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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