Re: [10GBT-Cabling] Re: [10GBASE-T] channel model
Frequency range of channel characterization should be such
that it would allow the fair evaluation of various line-
signalings. 1 GHz characterization, similar to that of Larry's,
would help us to reach that goal.
Joseph N. Babanezhad
> Thanks for getting this started.
> Your contribution addresses (at least) three significant elements of
> the channel model development:
> 1. frequency range of channel characterization
> 2. the use of temperature dependent transmission models
> 3.proposed model limits (with supporting measurement data)
> We should try to reach consensus on the elements.
> 1. The modeling ad hoc should reach a consensus on the frequency
> range of channel characterization. Note:We should limit the channel
> characterization to account for relevant signal spectrum and
> minimize excess bandwidth characterization.
> 2. The 10GBASE-T study group should reach consensus on temperature
> dependencies (in the objectives?).
> 3. I'm in the process of developing a straw proposal for the cabling
> ad hoc to address the generation of measurement data. Note: We
> need the resolution of the frequency range of channel
> charcterization (1).
> Chris DiMinico
> Chair Cabling Ad Hoc
> MC Communications
> e-mail: email@example.com
> In a message dated 1/29/03 1:33:04 AM Eastern Standard Time,
> firstname.lastname@example.org writes:
> << Attached is a proposed 100 meter Cat 5e channel model for
> 10GBaseT study
> (CHANMOD.TXT). This model is defined by complex-valued (X + jY
> format) insertion gain in the at 500 kHz intervals from DC to 1 GHz.
> The proposed model is derived from measurement (at 20 C) of a 100
> meter channel (with Cat 5e patch cords and 4 Cat 5e RJ45 connector
> interfaces). The baseline 100 meter channel model was temperature
> corrected to 50 C. (122
> F.) using the procedure defined in ASTM D4566 Section 26.4. The
> above mentioned temperature correction method modifies the magnitude
> but not the phase of the insertion loss. Experimental measurements
> confirm that temperature effects on the phase are minimal so the
> approximation is sufficiently accurate.
> The most recent proposed model is an extrapolation of the ISO 11801
> Class D channel loss limit. The ISO 11801 Class D limit is designed
> to accommodate expected worst-case measurements below 100 MHz and
> consequently includes some additional margin to meet this
> requirement. Since this limit is only specified below 100 MHz,
> extrapolation of the limit through smooth curve fitting becomes
> less accurate as it is extended farther beyond its defined
> boundaries. The new proposed model is based upon measurements
> beyond 500 MHz and thus validated to at least 500 MHz (and somewhat
> beyond 500 MHz). As shown in the attached graphs (CHANMOD.DOC), the
> insertion loss for the proposed model differs from the ISO 11801
> Class D 2002 channel limit by less than 0.2 dB from DC to 50 MHz and
> less than 0.5 dB from 50 to 100 MHz. While it does not represent an
> absolute worst-case channel, it represents a reasonable model for a
> feasibility study simulating a maximum length channel under worst-
> case temperature conditions.
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