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John, et al, I’m not going to be in In my opinion, Charles, Matt, and I have the most
accurate perspective of the problem since we’ve actually performed and
published EIT testing on real transceivers. For KX, KX4 and KR testing, Charles
and I used a channel that closely matched the Goergen channel (26dB@5.16GHz) and saw crosstalk tolerances of
450, 180, and ~2mV@BER 1E-12 respectively. The power summed crosstalk from
Tyco, Molex, and Intel NEXT, FEXT shows 20-100mVp@BER 1E-12 aggression to the
thru signal, so the crosstalk tolerance limits are in the ballpark. Matt found
that crosstalk tolerance results on a ~23dB@5.16GHz
channel were ~30mV below the 20dB channel for KR operation. EIT test results
documents are here: http://grouper.ieee.org/groups/802/3/ap/public/jun05/sawyer_02_0605.pdf http://grouper.ieee.org/groups/802/3/ap/public/sep05/sawyer_01_0905.pdf http://grouper.ieee.org/groups/802/3/ap/public/sep05/brown_01_0905.pdf Real measured data is a compelling argument, and so
far we have seen, 4 out of 4 vendors (2 unpublished) that are either borderline
or failing EIT (last Fall’s definition) testing for KR. The 802.3ap
channels’ PCBs and connectors were designed years ago for ~XAUI data
rates, and appear to be the best opportunity for improvement (larger signal with
reduced PNA, hence reduced DCD) in this system to enable KR operation. Is there a compelling argument against a 0.75m
channel? - From: DAmbrosia, John F
[mailto:john.dambrosia@TYCOELECTRONICS.COM] Technically speaking only Cases 1,2,and 3
fail the 20dB spec at Nyquist. You need to be careful in making a
statement like going to a 20dB channel. As you pointed out many channels
failed that number, but I believe those are all the 1m channels or stub limited
channels that are failing it. The channels that are meeting that the
number in general are the 0.75m. The potential ramifications could be
that to meet the 20dB channel we consider changing our reach objective to 0.75m.
John -----Original
Message----- Charles, The difference (no pun intended)
shows up in the differential vs single ended S-Parameters. I plotted SDD21 and
S21 for modITTC23withCoupler.s4p, and there is 1.428dB difference at 5.160GHz.
See attached. Sorry I had to be at another
meeting at noon, but I like the idea of going to a 20dB channel. In my opinion
that’s the lever big enough to get a real system working. Unfortunately
several (8 Molex, 4 Tyco, 3 Intel) channels violate that SDD21 up to 5GHz. See
attached. - From: Charles Moore
[mailto: guys, -- |--------------------------------------------------------------------|| Charles Moore | Avago Technologies| Image Solutions Division| charles.moore@avagotech.com| (970) 288-4561|--------------------------------------------------------------------| |