Re: [10GBT] Request for Cat6 Emissions Characteristics
Jose,
Please point out which lines in the matlab code I distributed, spectra.m,
have "bugs".
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: Wed, 21 Jul 2004 12:14:42 -0700
>
>Sailesh,
>
>It appears you have a bug in your program. You are assuming that PAM12
>is transmitting 0.8dB more power than PAM8 which is unfair. When you
>correct for this PAM12 should have better EMI.
>
>Jose
>
>Details:
>
>When I compute the total power transmitted for the PAM8 case by
>integrating the PSD I get 4.1dBm
>
>10*log10(sum(10.^((f8mag-116)/10)))+60 = 4.1dBm
>
>But when I compute the total power tx for the PAM12 case I get 4.9dBm
>
>10*log10(sum(10.^((f12mag-116)/10)))+60 = 4.9dBm
>
>
>PS. You probably made a mistake in the Butterworth filtering sampling
>rate adjustment or in a amplitude/power log mix-up.
>
>
>-----Original Message-----
>From: stds-802-3-10gbt@IEEE.ORG [mailto:stds-802-3-10gbt@IEEE.ORG] On
>Behalf Of sailesh rao
>Sent: Wednesday, July 21, 2004 9:37 AM
>To: STDS-802-3-10GBT@LISTSERV.IEEE.ORG
>Subject: Re: [10GBT] Request for Cat6 Emissions Characteristics
>
>Jose,
>
>It turns out that when you take into account the analog filtering and do
>an accurate calculation of the PSD/"EMI PSD", neither PAM8 nor PAM12 has
>an advantage in terms of EMI. I'm attaching the PDF ouput and the matlab
>code to generate the PSDs using both Ungerboeck's analog filter
>construction (3rd order BW LPF at fs/4) and using the (0.75+0.25D)
>approach used in our July presentation (with 5th order BW LPF at fs/2).
>In both cases, the peaks for the so-called "EMI PSD"s are within 0.01dB
>of each other for PAM8 and PAM12.
>
>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: Wed, 21 Jul 2004 00:06:30 -0700
> >
> >
> >
> >
> >All,
> >
> >From talking to several 10GBase-T EMI experts, the general consensus is
>
> >that EMI emissions increase with frequency as 20*log10(f).
> >
> >Thus the system with the higher symbol rate (PAM8 at 1000MHz) will have
>
> >worse EMI if the tx power is the same and both have equivalent digital
> >and analog filtering.
> >
> >The plot below shows the EMI PSD for 1GBase-T, PAM12 and PAM8 assuming
> >all have the same digital filter 3/4+1/4D. As expected the PAM8 is the
> >worse, since it has the most signal at higher frequencies.
> >
> >
> >
> >I only plotted the PSD up to 0.4*SymbolRate, because the analog filters
>
> >will typically have >3dB attenuation at 0.5*Symbol rate and the PSD is
> >mostly dependent on the analog filters. PAM12 and PAM8 will both have
> >similar analog filters.
> >
> >For those interested in the details I included the matlab code. For a
> >fixed tx power the PSD level (dBm/Hz) will drop as -10*log10(BW) when
> >we increase the bandwidth, BW. But as we increase the BW, the EMI
> >increases as 20*log10(BW). Clearly the increase in EMI in PAM8 is twice
>
> >as bad as the PSD level drop.
> >
> >Thus PAM12 has 10*log10(1000)=0.8dB more signal at low frequencies, but
> >PAM8 has 1.6dB more EMI at high frequencies. Therefore PAM8 has 0.8dB
> >more EMI
> >
> >Jose
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >
> >-----Original Message-----
> >From: stds-802-3-10gbt@IEEE.ORG [ <mailto:stds-802-3-10gbt@IEEE.ORG>
> >mailto:stds-802-3-10gbt@IEEE.ORG] On Behalf Of sailesh rao
> >Sent: Tuesday, July 20, 2004 6:55 PM
> >To: STDS-802-3-10GBT@listserv.ieee.org
> >Subject: [10GBT] Request for Cat6 Emissions Characteristics
> >
> >Hi All,
> >
> >At the request of a task force member, I computed the transmit PSD for
> >PAM8,
> >PAM12 and 1000BASE-T, and discovered that I added the contribution of
> >Jose's 0.4dB incorrectly in my Total EMI Penalty calculations in the
> >updated table.
> >Actually, in the passband, the transmit PSD for PAM8 after THP is 1.6dB
>
> >lower than the transmit PSD for PAM12 after THP, and not 0.8dB lower as
>
> >I had reported earlier.
> >
> >However, rather than simply adding another 0.8dB to the PAM12 EMI
> >penalty, I would like to propose that we compute the estimated
> >emissions characteristics of the PAM8/PAM12 transmit PSDs, for
> >different transmit filtering choices, over typical Cat6 cabling and
> >assess the difference in peaks to estimate the true emissions penalty
> >for one PAM approach over the other. I know Scott Powell had published
> >a PDF version of measured 4-connector Cat6 emissions characteristics
> >for a flat transmit PSD (powell_1_0303.pdf), but do cabling experts
> >agree with Scott's measurements and can the task force use that data to
>
> >assess the emissions characteristics of PAM8 vs. PAM12? If so, I would
> >like to request Scott to publish a file version of his measurements on
> >the task force web site so that we can all use it to do fair
> >comparisons. If not, are there other typical Cat6 cabling emissions
> >measurements that we can use to do the emissions comparisons?
> >
> >Any input from the cabling experts on the reflector would be greatly
> >appreciated.
> >
> >Regards,
> >Sailesh Rao.
> >srao@phyten.com
> >
> >_________________________________________________________________
> >Don't just search. Find. Check out the new MSN Search!
> > <http://search.msn.click-url.com/go/onm00200636ave/direct/01/>
> >http://search.msn.click-url.com/go/onm00200636ave/direct/01/
> >
> >
> >
> ><< PSDPAM12andPAM8.m >>
>
>_________________________________________________________________
>Is your PC infected? Get a FREE online computer virus scan from
>McAfee(r) Security.
>http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963
_________________________________________________________________
Is your PC infected? Get a FREE online computer virus scan from McAfeeŽ
Security. http://clinic.mcafee.com/clinic/ibuy/campaign.asp?cid=3963