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Re: [10GBT] Request for Cat6 Emissions Characteristics



Jose,

You appear to have a valid point. I'll check the scaling used in these
matlab functions and get back to you.

However, for the sake of this task force chair, I hope you are wrong. If I
have to lower the 1000BASE-T PSD by ~10dB, I'm afraid that some members of
our working group will eat Brad Booth alive on the 10GBASE-T emissions
issue.

Meanwhile, I renew my request to Scott Powell to please publish a file
version of the emissions characteristics he used to compute the contents of
slide 6 of powell_1_0704.pdf.

Regards,
Sailesh Rao.
srao@phyten.com

----- Original Message -----
From: "Jose Tellado" <JTellado@TERANETICS.COM>
To: <STDS-802-3-10GBT@listserv.ieee.org>
Sent: Wednesday, July 21, 2004 7:10 PM
Subject: Re: [10GBT] Request for Cat6 Emissions Characteristics


>Sailesh,
>
>There must be something wrong with the code, when the integral of the
>1GBaseT PSD power is 15dBm (details below).
>
>I thought I gave you a good hint, and I rather you debug your code.
>
>The problem is likely in your modeling of the digital/analog sampling
>rate conversion, lines 12-35.
>You can check the 3rd chapter of (or any other introductory DSP book):
>Oppenheim and Shafer, "Discrete Time Signal Processing". It's eq (3.49)
>in my undergrad international edition.
>
>Jose
>
>
>1GBase-T power details:
>
>10*log10(sum(10.^((f5mag-116)/10)))+60 = 15.3dBm
>
>This equation computes the (discrete) integral of the PSD, where
>(f5mag-116) is the PSD from your code, and 60dB converts from MHz to Hz.
>
>
>
>-----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 3:29 PM
>To: STDS-802-3-10GBT@listserv.ieee.org
>Subject: 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
> > >
> > >_________________________________________________________________
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> > >
> > >
> > >
> > ><< PSDPAM12andPAM8.m >>
> >
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