Re: [10GBT] Request for Cat6 Emissions Characteristics
Sailesh
This time you are correct, each wire will have an averaged maximum
"peak" of 0.02dB on all 4 wires "simultaneously".
At the Q&A session after Hugh's presentation the cabling and test
equipment experts described that measuring with 0.1dB accuracy was not a
simple task.
Jose
PS But you still need to check your math on the framing size, it's
larger than 1 micro.
-----Original Message-----
From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On
Behalf Of sailesh rao
Sent: Saturday, July 24, 2004 4:21 PM
To: STDS-802-3-10GBT@listserv.ieee.org
Subject: Re: [10GBT] Request for Cat6 Emissions Characteristics
Folks,
This gets worse. A closer reading of tellado_1_0704.pdf reveals that
fixed patterns are being sent once every microsecond on all 4 wire pairs
simultaneously!
Talk about peaky PSD bumps in the PAM12 transmit spectra, yikes!
Regards,
Sailesh Rao.
srao@phyten.com
>From: sailesh rao <sailesh_rao@HOTMAIL.COM>
>Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@listserv.ieee.org>
>To: STDS-802-3-10GBT@listserv.ieee.org
>Subject: Re: [10GBT] Request for Cat6 Emissions Characteristics
>Date: Sat, 24 Jul 2004 15:10:58 -0400
>
>Seki,
>
>I disagree that the "ripple is small". If we keep sending the same
>pattern over and over, once every MHz, the ripple won't be small. It is
>technically incorrect to pretend otherwise.
>
>Heck, I have a good mind to add a large number of dBs to the PAM12
>Total EMI penalty to account for this problem.
>
>In HDSL2, the frequencies were too low to cause any emissions concerns.
>
>Regards,
>Sailesh Rao.
>srao@phyten.com
>
>>From: "K. Seki" <k_seki@MTC.BIGLOBE.NE.JP>
>>Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@listserv.ieee.org>
>>To: STDS-802-3-10GBT@listserv.ieee.org
>>Subject: Re: [10GBT] Request for Cat6 Emissions Characteristics
>>Date: Sat, 24 Jul 2004 18:05:04 +0900
>>
>>Sailesh,
>>
>>As Jose mentioned, PAM12 has 1dB lower EMI PSD around 200MHz than
>>PAM8, even if adding 0.02dB of ripple.
>>I am not expert on EMI, but I don't think that the ripple have
>>meaningful effect on EMI, becuse the ripple is very small.
>>Furthermore, HDSL2 have already applied a similar PAM2 frame alignment
>>method.
>>I would appreciate any input from the EMI experts.
>>
>>Regards,
>>Seki
>>
>>-----Original Message-----
>>From: sailesh rao <sailesh_rao@HOTMAIL.COM>
>>Sent: Sat, 24 Jul 2004 03:23:39 -0400
>>Subject: Re: [10GBT] Request for Cat6 Emissions Characteristics Jose,
>>
>>It is interesting to note that your frequency range of interest has
>>now narrowed down to "in the range of 200MHz".
>>
>>Frankly, I think you are being too cavalier about the peaky PSDs in
>>the
>>PAM12 proposal in the 200MHz-300MHz frequency range. Given the peaky
>>PSDs at the start of each frame in your proposal (i.e., once every
>>52,833 bits), I'm afraid that at 10Gb/s these peaks occur often enough
>>for the FCC to become very interested in them.
>>
>>If you now think that you will "scramble the frame start bits", may I
>>ask why you didin't think of this scrambling last month? It is blatant
>>omissions like these that can sink a standard.
>>
>>Regards,
>>Sailesh Rao.
>>srao@phyten.com
>>
>> >From: Jose Tellado <JTellado@TERANETICS.COM>
>> >Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@listserv.ieee.org>
>> >To: STDS-802-3-10GBT@listserv.ieee.org
>> >Subject: Re: [10GBT] Request for Cat6 Emissions Characteristics
>> >Date: Fri, 23 Jul 2004 23:40:25 -0700
>> >
>> >
>> >Sailesh,
>> >
>> >As Glenn described, when you corrected spectra.m (which improved
>> >PAM12) you did eliminate your original "EMI PSD" plots.
>> >
>> >We all understand that EMI is a complicated problem and hopefully
>> >it's not an issue, but I don't think you should omit results that
>> >can be useful to the group to evaluate. Attached is your revised
>> >code with all four plots included (I just had to copy from your
>> >original code) plus the FCC and CISPR EMI shapes.
>> >
>> >Based on your corrected code and the EMI limits you provided, it
>> >appears that the most problematic region is around 200MHz and in
>> >this area PAM12 is up to 1dB better,
>> >
>> >Jose
>> >
>> >
>> >PS On the peaky PSD issue, the sync pattern highest peak is 23dB
>> >below the signal PSD. This adds about 0.02dB of ripple. I don't
>> >think test equipment can even measure this. But if you think this
>> >ripple is too high we can always scramble it :)
>> >
>> >10*log10(1 + 10^(-23/10)) = 0.0217 dB
>> >
>> >
>> >
>> >
>> >-----Original Message-----
>> >From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG]
>> >On Behalf Of sailesh rao
>> >Sent: Friday, July 23, 2004 10:03 PM
>> >To: STDS-802-3-10GBT@listserv.ieee.org
>> >Subject: Re: [10GBT] Request for Cat6 Emissions Characteristics
>> >
>> >Glenn,
>> >
>> >There are several reasons I stated for why this calculation is
>> >incorrect.
>> >
>> >1. In the passband (upto ~0.25fs), where we can do nothing about the
>> >transmit PSD, PAM12 is 0.8dB higher than PAM8. This is the killer
>> >portion of the frequency band as far as emissions are concerned,
>> >since we can filter out the higher frequencies without incurring
>> >much penalty in the receiver performance.
>> >2. You appear to be focusing on a narrow region of the frequency
>> >band above 200MHz. If you are concerned with this narrow frequency
>> >band, please note from the attached that the FCC and CISPR limits
>> >increase in that frequency band. These changes in limits should be
>> >taken into account in any such "peak EMI PSD" calculations that you
>> >are doing. The reason I deleted this portion of my matlab code was
>> >because I didn't have the exact frequencies at which these steps
>> >occur, and I didn't want to make another mistake and provoke another
>> >round of highly disrespectful e-mails on the reflector.
>> >3. Emissions optimizations cannot be done by just doing some 20log10
>> >calculations on average PSDs and selecting the system that shows the
>> >lowest peak. For instance, the PAM12 proposal uses periodic frame
>> >start symbols that have "peaky" PSDs (see, e.g., the PSD "bumps" on
>> >slide 26 of tellado_1_0704.pdf). You are guaranteed to get much
>> >higher peaks in the 200-300MHz range for the PAM12 proposal because
>> >of the addition of these PSD bumps. Therefore, just looking at the
>> >average PSD is insufficient for "estimating" emissions.
>> >
>> >In any case, the PAM12 EMI penalty is well over 4dB for existing
>> >cabling.
>> >This is a huge hole that the PAM12 proponents are trying to climb
>> >out of, and I don't see how we can go before IEEE 802.3 and claim
>> >
>> >1. 10GBASE-T is an extremely hard problem, which requires the
>> >10GBASE-T PHY solution to operate very close to the Shannon limit.
>> >2. The task force decided to choose PAM12 that has a 4dB EMI penalty
>> >over PAM8, because the task force decided that these 4dBs are not
>> >that important.
>> >
>> >(2) contradicts (1) and therefore, don't you think that we will get
>> >our clocks cleaned at the working group level?
>> >
>> >Regards,
>> >Sailesh Rao.
>> >srao@phyten.com
>> >
>> >
>> >That is a completely untenable
>> > >From: Glenn Golden <gdg@zplane.com>
>> > >Reply-To: gdg@zplane.com
>> > >To: STDS-802-3-10GBT@listserv.ieee.org
>> > >Subject: Re: [10GBT] Request for Cat6 Emissions Characteristics
>> > >Date: Fri, 23 Jul 2004 21:24:32 -0600
>> > >
>> > >
>> > >On Thu, 22 Jul 2004 16:07:12 Sanjay Kasturia wrote:
>> > > >
>> > > > This makes me doubt the objectivity of your analysis.
>> > > >
>> > >
>> > >
>> > >On Thu, 22 Jul 2004 16:52:22 "Kardontchik, Jaime" wrote:
>> > > >
>> > > > I would suggest to delete the remark about "objectivity".
>> > > > It is really unwarranted.
>> > > >
>> > > > Everyone is trying to do the best possible technical analysis
>> > > > in real-time.
>> > > >
>> > > > It happens that the ones that dare offer their code for public
>> > > > scrutiny in order to advance the discussions, end up being
>> > > > criticized for the incompletness, inaccuracies, etc, of their
code.
>> > >
>> > >
>> > >I'm not sure that Sanjay's remark had to do with Sailesh's program
>> > >having a bug. Everyone understands that honest mistakes of this
>> > >sort will occasionally be made, and that public stonings on the
>> > >reflector are not appropriate. I think Sanjay's remark may have
>> > >had to do with what happened after the error was pointed out and
corrected.
>> > >
>> > >In his original posting (based on the computations prior to the
>> > >bug
>> > >fix) Sailesh showed four plots: Two large scale, and also two
>>zoomed-in
>> >
>> > >"EMI PSD" plots. Only the latter two include the 20log(f) radiated
>> > >emission frequency dependence, which, in past postings, Sailesh
>>himself
>> >
>> > >has specifically pointed out as being relevant to EMI
considerations.
>> > >On those zoomed-in plots, he made a point of noting that the
>> > >differential between the PAM8 and PAM12 peaks was trivial:
>> > >
>> > > >
>> > > > In both cases, the peaks for the so-called "EMI PSD"s are
>> > > > within 0.01dB of each other for PAM8 and PAM12.
>> > > >
>> > >
>> > >But in the subsequent posting, after the bug was fixed, the
>> > >zoomed-in EMI PSD plots with the 20log(f) factor were omitted, and
>> > >nothing was said about the relationship between the PAM8 and PAM12
>> > >peaks. This omission was justified with the following dismissive
comment:
>> > >
>> > > > Besides, in any case, the FCC limits for emissions increases in
>> > > > the neighborhood of 220MHz, thereby rendering Jose's emissions
>> > > > contentions completely irrelevant.
>> > >
>> > >and later
>> > >
>> > > > I consider the point Jose made about the emissions issue to be
>> > > > pure specmanship, and I've already stated that it is completely
>> >irrelevant.
>> > >
>> > >I think Sanjay's response probably had to do with the lack of
>> > >clear technical basis with this claim was made, and with the
>> > >curious way
>>that
>> >
>> > >plots which had been relevant prior to the bug fix became "totally
>> > >irrelevant" after it was corrected, since the actual plots -- had
>> > >they been included in the posting -- do not seem to support that
>>contention.
>> > >
>> > >The plots are attached, along with original (erroneous) plots:
>> > >
>> > > 7525_orig.gif 0.75_0.25D filter, original
(erroneous)
>> >results
>> > > 7525_corr.gif " " corrected results
>> > >
>> > > unger_orig.gif Ungerboeck filter, original
(erroneous)
>> >results
>> > > unger_corrected.gif " " corrected results.
>> > >
>> > >These were produced using the original and corrected spectra.m
>>programs
>> >
>> > >respectively, with changes made only to the axis limits so as to
>> > >focus in on the claims being made about the behavior near the
peaks.
>> > >
>> > >In the corrected EMI PSD plots -- the ones that incorporate
>> > >20log(f) and were omitted from Sailesh's second posting -- even if
>> > >one completely ignores the energy above 216 MHz [I think that's
>> > >where the actual Part
>> > >15 mask breakpoint is] PAM12 has a lower peak value for both
filters.
>> > >For the Ungerboeck design, both peaks occur below 216 MHz, and the
>>peak
>> >
>> > >differential -- which Sailesh was interested in pointing out
>> > >earlier when his numbers were wrong and showed no penalty for PAM8
>> > >-- is now
>> > >0.8 dB in favor of PAM12.
>> > >
>> > >So, as far as the actual data at hand goes, it seems disingenuous
>> > >to use the step in the EMI mask as justification for dismissing
>> > >Jose's claim as "totally irrelevant", when in fact for one of the
>> > >filters, it supports exactly the opposite conclusion.
>> > >
>> > >It may well be true that when the smoke clears on this issue,
>> > >neither system is significantly different as regards peak EMI.
>> > >But the
>>present
>> >
>> > >data does not make that case, and dismissing it with a verbal
>> > >flourish does not help to advance the discussion.
>> > >
>> > >
>> > >Glenn Golden
>> > >Principal Engineer
>> > >Teranetics, Inc.
>> > >ggolden@teranetics.com
>> > >
>> > ><< unger_corrected.gif >>
>> > ><< unger_orig.gif >>
>> > ><< 7525_corr.gif >>
>> > ><< 7525_orig.gif >>
>> >
>> >_________________________________________________________________
>> >Overwhelmed by debt? Find out how to 'Dig Yourself Out of Debt' from
>> >MSN Money. http://special.msn.com/money/0407debt.armx
>> >
>> ><< EMIPSDSaileshCode.pdf >>
>> ><< spectraAllPlots.m >>
>>
>>_________________________________________________________________
>>Don $BCU (B just search. Find. Check out the new MSN Search!
>>http://search.msn.click-url.com/go/onm00200636ave/direct/01/
>
>_________________________________________________________________
>Don't just search. Find. Check out the new MSN Search!
>http://search.msn.click-url.com/go/onm00200636ave/direct/01/
_________________________________________________________________
Overwhelmed by debt? Find out how to 'Dig Yourself Out of Debt' from MSN
Money. http://special.msn.com/money/0407debt.armx