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Jack,
I was trying for the worst case for common mode radiation.
There were not any differential mode signals generated, except by mode conversion.
The results are ball park in any case.
What you ask for is possible, but not what I was trying to do.
I wanted to add one data point for what common mode noise could be tolerated from the PSE power supply,
given Roger's conclusion that radiated emission requirements are the more restrictive limit for power supply noise.
A conclusion that I agree, by the way, with for frequencies of 30 MHz and higher.
I did this EMC testing as a freebie, I don't have a plan to redo this EMC testing.
If I do any testing in the future, I will keep your request in mind.
thanks,
- Rick
-----Original Message-----
From: Jack Andresen [SMTP:jandresen@etslan.com]
Sent: Friday, September 15, 2000 1:55 PM
To: Brooks, Rick [SC5:321:EXCH]
Cc: stds-802-3-pwrviamdi@ieee.org
Subject: Re: RJ-45 common mode radiated emissions testing
Rick,
The data helps. However, is it possible to redo with proper terminations
on the end of the cable. You need both differential and common mode
terminations. Unterminated end reflections will increase mode
conversion.
Jack Andresen
*************************
Rick Brooks wrote:
>
>
> I have posted the test setup and results of a radiated emissions test
> that I did recently in a 10 meter anechoic chamber.
>
> The test was to try to determine what common mode signal voltage would
> produce a radiated field that would be at the
> compliance limit, class B in this case.
> I hope that this data will help us to specify a noise requirement for
> the DTE power from the PSE, as well as the PD.
>
> It is important to understand that the radiated emissions requirements
> only cover from 30MHz and higher.
> The spectral region from 500 kHz to 30 MHz, is obviously of importance
> to 10/100/1000, but I don't cover it here.
>
> The pdf file is at:
>
> ttp://www.ieee802.org/3/power_study/public/email_attach/RJ45_rad_emissions.pdf
>
> comments, questions?
>
> thanks,
> - Rick