Re: [10GBT] FW: [10GBT] PAM8 and PAM12 sys time domain analysis
Albert,
I agree with you that using higher order low pass filters for emissions
control has practical consequences for the 10GBASE-T implementation.
However, the PAM12 proposal did include a 3rd order BW low-pass filter with
a 3dB point at 206MHz in the transmitter.
The transmitter specification in the 10GBASE-T standard will be at the MDI,
just as it was in the 1000BASE-T standard, and this would include the effect
of the transformer. Are you suggesting that the 10GBASE-T PMA section should
discount the effect of the transformer when calculating the peak voltage in
the pulse template specifcations?
Regards,
Sailesh Rao.
srao@phyten.com
>From: "Booth, Bradley" <bradley.booth@INTEL.COM>
>Reply-To: "IEEE P802.3an" <STDS-802-3-10GBT@LISTSERV.IEEE.ORG>
>To: STDS-802-3-10GBT@LISTSERV.IEEE.ORG
>Subject: [10GBT] FW: [10GBT] PAM8 and PAM12 sys time domain analysis
>Date: Wed, 11 Aug 2004 12:23:34 -0700
>
>Sailesh,
>
>In the studied PAM8 and PAM12 systems the Tx launch level was
>fixed at 1 Vp (popular with many phy vendors) before the Tx
>filter. So, the actual tx power at MDI is reduced due to the
>filtering effects.
>
>Alternatively, the Tx power could be maintained at a const. level
>at MDI -- this is irrespective of a Tx filtering scheme.
>
>Pls refer to ungerboeck_1_0704.pdf, slide 22 -- the Tx pwr is
>5 dBm at the LPF output. To achieve this objective, one needs the
>PAM level at app. 1.3 Vp. Due to PAM pdf transformation via high
>order filtering, the LPF output peaking will be higher than 1.3 V:
>1.64 Vp has been observed over a 67 kBaud time interval for the
>above quoted example.
>
>Hope, this clarifies.
>
>Regards,
>Albert
>
>
>
>
>sailesh rao wrote:
>
>
>Albert,
>
>As you know, the PAM12 proposal (powell_1_0704.pdf, slide 6) used a 3rd
>order Butterworth low-pass transmit filter with a 3dB point at
>206.25MHz.
>This filter has an attenuation of 18dB at fs/2=412.5MHz, which dwarfs
>the
>attenuation due to the magnetics that you are showing. The SNR margin
>loss
>due to this transmit filter is actually only around 1dB.
>
>Therefore, I'm not sure of your calculations without having access to
>the
>channel+magnetics attenuation curve that you are using. Can you please
>share
>the equational form of this curve so that I can understand what you are
>getting at?
>
>In any case, please note that with the reduced symbol rate of
>952.381Ms/s,
>the PAM8 system will gain at least 1dB of additional SNR margin in Model
>3,
>which should improve the situation considerably in your simulations.
>
>Regards,
>Sailesh Rao.
>srao@phyten.com
>
>
>
>From: Albert Vareljian <mailto:albertv@IEEE.ORG> <albertv@IEEE.ORG>
>Subject: Re: [10GBT] PAM8 and PAM12 sys time domain analysis
>Date: Thu, 5 Aug 2004 10:44:34 -0700
>
>Sailesh,
>
>When the line transformers (specified roughly as per
>presentations the group has seen so far) are included in the
>analysis -- the channel shows additional ~5.6 dB of loss at
>500 MHz. See attached graph.
>
>This, combined with Tx 1 Vp launch constraint at the IC, but
>not at MDI, accounts for the bulk of SNR losses w.r.t. "ideal"
>Class E channel Salz SNR.
>
>The actual SNR loss in the time-domain bench vs. its frequency
>domain reference proves to be below 1 dB -- this would be a very
>hard target to achieve for any practical h/w implementation of
>10GBASE-T.
>
>Regards,
>
>Albert
>
>
>
>
>
>
>sailesh rao wrote:
>
>
>
>Albert,
>
>I assumed that the reference to Model 3 in your report included ANEXT
>with a
>64.5dB intercept and other worst-case impairments, as agreed upon in the
>
>task force.
>
>If there was no ANEXT or residual Echo/NEXT/FEXT in your simulations,
>then I
>calculate the implementation loss in your simulations to be at least
>3.6dB
>for PAM8 and at least 4.0dB for PAM12.
>
>I don't think we should be contemplating such implementations for
>10GBASE-T.
>
>Regards,
>Sailesh Rao.
>srao@phyten.com
>
>
>
>From: Albert Vareljian <mailto:albertv@IEEE.ORG> <albertv@IEEE.ORG>
>Subject: Re: [10GBT] PAM8 and PAM12 sys time domain analysis
>Date: Fri, 30 Jul 2004 00:20:13 -0700
>
>Hi Jose,
>
>No ANEXT or other impairments except -140dBm/Hz were employed in sims
>covered in the report.
>
>Adding ANEXT would seem to be the next logical step. However, correctly
>modeling ANEXT may prove a bit tricky.
>
>As we already discussed on IEEE floor -- our agreed ANEXT models
>are specified only in terms of the frequency domain magnitude (no
>phase). So, the time-domain implementation has been left open up
>to the user...
>
>There could be many interpretations as to how one arrives at a
>reasonably behaved time-domain ANEXT TF and its excitation method.
>Our analysis indicates that end results in the system could vary
>significantly on the case by case basis, depending on the methodology
>used to model time-domain ANEXT behavior.
>
>Based on the above, it may be helpful if the group agrees on and adopts
>some "uniquely" defined causal, scalable time-domain capable model
>for ANEXT that could be used for system qualification. One possible
>example of ANEXT TF implementation in s-domain (usable in time- and
>frequency- sims) is illustrated in the attachment.
>
>
>Regards,
>
>Albert
>
>
>
>
>Jose Tellado wrote:
>
>
>
>Hi Albert,
>
>Thank you for your detailed time-domain report, I have a couple of
>simple questions on the simulation assumptions.
>
>Have you included the effects of ANEXT in these simulations? If so,
>what
>approved PHY channel model (1-4) would this approximate?
>
>Did you include other receiver impairments such as residual EC/NX/FX or
>did you lump all these effect into the -140dBm/Hz noise?
>
>Regards,
>Jose Tellado
>
>
>
>-----Original Message-----
>Sent: Monday, July 26, 2004 7:57 PM
>Subject: [10GBT] PAM8 and PAM12 sys time domain analysis
>
>Hi All,
>
>Pls find attached pdf report on PAM8 and PAM12 systems time domain
>simulation and comparative analysis.
>
>Regards,
>
>Albert Vareljian
>
>
>
>
>
><< ANEXT_Fig.doc >>
>
>
>
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