RE: CRPAT / CJPAT Pattern Question
John,
Absolutely agree. I was just simplifying my description to one lane, but, I
assumed we would test each lane individually. As far as the pattern
selection is concerned, the use of different patterns on each lane allows us
to see the contribution each of the other lanes has on cross talk noise.
For example, suppose Lane 1 was driving a /5 clock like pattern (1111100000)
the FFT of the jitter on the Lane under test would show a spectral line at
Fc/10 and the amplitude of the spectral line would be the pk-pk impact on DJ
that Lane 1 has on the Lane Under Test (LUT?). We could set up the other 3
lanes with varying degrees of clock like patterns and quickly estimate each
lanes contribution to crosstalk on the LUT. We could perform this test on
all 4 lanes to measure crosstalk contribution. It would also be interesting
to sweep through several clock like frequencies on the non tested lanes to
quantify the impact of crosstalk as a function of instantaneous frequency.
The test in which we apply the same pattern on all of the non tested lanes
will tell us how the crosstalk components combine.
Regards,
Michael
-----Original Message-----
From: DAmbrosia, John F [mailto:john.dambrosia@xxxxxxxxxxxxxxxxxxx]
Sent: Thursday, June 14, 2001 9:11 AM
To: 'Michael Debie'; 'Serial PMD reflector (E-mail)'
Subject: RE: CRPAT / CJPAT Pattern Question
Michael,
I think your second proposal makes more sense, but i think it would need to
go one step further. I think we should cycle which lane is the "different"
lane like this-
Pat 1A Pat 1B Pat 1C Pat 1D
Lane A + - - -
Lane B - + - -
Lane C - - + -
Lane D - - - +
Where the "+" lane would be the pattern, and the "-" would be the
compliment. Thus, all channels get examined. If only 1 lane is tested,
then the test is specific to the implemenation, where if all lanes in a
channel get examined, then the performance of the channel is fully examined
rather than 1/4 of it.
John
-----Original Message-----
From: Michael Debie [mailto:mdebie@xxxxxxxxxxxxx]
Sent: Wednesday, June 13, 2001 5:41 PM
To: DAmbrosia, John F
Subject: RE: CRPAT / CJPAT Pattern Question
John,
A good diagnostic for cross talk would be to place different frequency clock
like patterns on all of the lanes. This could tell us the amplitude of
cross talk per other lane and where it comes from. Also, if we run the same
patterns on three lanes and one lane different, we could see how the other
three lanes combine to effect cross talk on the lane under test.
Regards,
m
-----Original Message-----
From: DAmbrosia, John F [mailto:john.dambrosia@xxxxxxxxxxxxxxxxxxx]
Sent: Wednesday, June 13, 2001 4:21 PM
To: Serial PMD reflector (E-mail)
Subject: CRPAT / CJPAT Pattern Question
Everyone,
The 10GEA XAUI Interoperability Group met this week, and were discussing the
use of the CRPAT / CJPAT patterns for its testing. A general observation
was that the same data pattern appear on all 4 lanes synchronously, which
means crosstalk is not really being testing, which was probably being
accounted for by connector crosstalk budget of 4%. Tyco presented data
http://grouper.ieee.org/groups/802/3/ae/public/may01/dambrosia_2_0501.pdf
that showed that crosstalk, which resulted from signals switching in-phase
(i.e. high to low or low to high), could actually improve the overall
response of the system. Thus, the resultant eye is improved and would be
best case, and not even nominal (all adjacent channels quiet).
Obviously, there are a lot of system variables that come into account when
considering crosstalk, but it would seem that we could improve the harshness
of these patterns by not making all 4 channels have the same data patterns.
John D'Ambrosia
Manager, Semiconductor Relations
Tyco Electronics Corporation
Tel. 717.986.5692
Mobile 717.979.9679
email - john.dambrosia@xxxxxxxxxxxxxxxxxxx