A couple of notes.
I used different port numeration - 1 and 2 are on the same side, 3 and 4 -
opposite.
Also, S-parameters for NEXT are always reciprocal S12=S21 and S34=S43.
However, if no symmetry along the link, cross-talk in time domain may be not
reciprocal due to differences in terminations of the links.
Yuriy
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Yuriy Shlepnev
Sent: Monday, May 3, 2021 1:03 PM
To: praveenkumardr@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: XTALK reciprocal ?
Hi Praveen,
You basically answered your question yourself.
The S12 and S34 (NEXT on opposite ends) are exactly the same with the
symmetry over the plane in the middle of the link
A1---|---B3
A2---|---B4
Otherwise, they may be different.
This is property of symmetrical system - nothing to do with the reciprocity.
It is easy to proof by using the symmetry group representations for
corresponding S-matrices - basic theory is in R.H. Dicke, The symmetry of
waveguiding junctions, 1964
Best regards,
Yuriy
Yuriy Shlepnev, Ph.D.
President, Simberian Inc.
www.simberian.com
Simbeor THz - Accurate, Productive and Cost-Effective Electromagnetic Signal
Integrity Software to Design Predictable Interconnects!
Simbeor SDK - The Industry-First Signal Integrity Analysis Automation Kit!
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Praveen Kumar
Sent: Monday, May 3, 2021 8:20 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] XTALK reciprocal ?
Suppose there are 2 transmission lines A (Port 1 & 2) & B (Port 3 & 4)
Is NEXT13 expected to be same as NEXT24 ?
Of course if the coupling is symmetric around the line equally dividing
transmission line A & B, then it is easier to say NEXT13 is same as NEXT24.
But If the coupling geometry is not symmetric, i.e, there could be
different coupling near Port 2 & 4 compared to coupling near Port 1 & 3.
Thanks
Praveen
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