Sanjay,
Short answer:
The traditional simple transmission line models utilized to predict far-end crosstalk (below 100 MHz) do
not account for common mode propagation (and termination) and neglect far-end reflections. Many of the
traditional references assume that like pairs in a cable have identical propagation constants (magnitude and phase),
and the lines are terminated in their characteristic impedance. These effects (combined) can result in measurable
differences between the FEXT of pair ij and the FEXT of pair ji.
Regrads,
Chris
In a message dated 5/12/2004 6:40:31 PM Eastern Standard Time, SKasturia@TERANETICS.COM writes:
Bryan,
Good question. I assumed that FEXT between pair i and j would be the
same as between j and i. Thinking about it some more, I am not sure if
that is correct. Can others let us know what measurements have revealed?
Chris DiMinico, can you answer this?
Sanjay
sanjay@teranetics.com
cell (650) 704-7686
office (408) 653-2235
-----Original Message-----
From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On
Behalf Of Sparrowhawk, Bryan
Sent: Wednesday, May 12, 2004 4:19 PM
To: STDS-802-3-10GBT@listserv.ieee.org
Subject: Re: [10GBT] Channel models
Sanjay,
I have a question about your terminology regarding far end crosstalk in
"c)".
Could you have meant twelve pair combinations for FEXT instead of 6?
Or do you speak of "Far end crosstalk" as others speak of 'reverse
NEXT'?
Bryan S.
-----Original Message-----
From: Sanjay Kasturia [mailto:SKasturia@TERANETICS.COM]
Sent: Friday, April 09, 2004 3:36 PM
To: STDS-802-3-10GBT@listserv.ieee.org
Subject: [10GBT] Channel models
We have four channel models defined from the March 2004 plenary meeting.
For detailed PHY performance simulations, we will need sample channel
data that complies with these models.
We will greatly appreciate it if any task force participants can provide
full matrix (4x4) channel data. This would ideally include:
a) Insertion loss data on each of four pairs - real and imaginary
b) Near end crosstalk coupling (6 unique pair-combinations) - real and
imaginary
c) Far end crosstalk coupling (6 unique pair-combinations) - real and
imaginary
d) Four unique echo transfer functions (one for each pair) - real and
imaginary
This can be obtained by measurements on actual cable and then scaling to
meet the specified channel models.
Any cable companies volunteering to provide this data?
There is some data from the cabling Ad-hoc available on:
http://www.ieee802.org/3/an/public/material/index.html
This data has some of the items listed above but not all. It does,
however, provide enough to get some sense of performance.
Sanjay Kasturia
sanjay@teranetics.com
cell (650) 704-7686
office (408) 653-2235