Re: [10GBT] Request for Cat6 Emissions Characteristics
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 >>
> >
> >_________________________________________________________________
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> >Money. http://special.msn.com/money/0407debt.armx
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> ><< EMIPSDSaileshCode.pdf >>
> ><< spectraAllPlots.m >>
>
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