[SI-LIST] Re: Gigabit ethernet compliance asymmetry test
- From: "Kihong Joshua Kim" <joshuakh@xxxxxxxxx>
- To: ruston_matt@xxxxxxx
- Date: Wed, 17 Oct 2007 11:24:19 -0400
For BER of about 10^-9, your 1% difference might give you roughly about
8.7*10^-9 and 7.1*10^-9 difference.
So my guess is you see the tendency on the conservativeness to introduce the
measurement uncertainty. In real life, I would says 'who cares?' for such a
small variation.
BUT if your are dealing with low SNR situation, by all means, stick to
this...
Anyway hope this will help...
Kihong Joshua Kim
SI in Photonics and Electronics
On 10/17/07, ruston_matt@xxxxxxx <ruston_matt@xxxxxxx> wrote:
>
> All:
>
>
> Hi. I was wondering if anyone on this list knows what the purpose of
> this compliance test for gigabit ethernet is. The test is the peak
> voltage asymmetry test for points "A" and "B"; they must match their
> peak voltage amplitudes to within 1%.
>
>
>
> How does measuring this asymmetry come into play (i.e. how does the
> symmetry affect my system in tangible terms)? If I have 1.5% asymmetry,
> does it shorten my maximum cable length and by what magnitude? How about
> 2% asymmetry? Does it increase my BER and by how much. What mechanisms
> are at work here? Or is this a test that has very little meaning on the
> functioning of a gigabit Ethernet link?
>
>
>
> Any insight/help is appreciated.
>
>
>
> Regards,
>
>
>
> Matt
>
>
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