[SI-LIST] Re: Ethernet emissions.
- From: Bryan Ackerly <bryan@xxxxxxxxxxxxxx>
- To: "leeritchey@xxxxxxxxxxxxx" <leeritchey@xxxxxxxxxxxxx>
- Date: Mon, 8 Apr 2013 12:15:53 +1000
Lee, I try to never cut up ground planes. This is the one "golden rule" i took
away from one your own training courses I attended many years ago....
Regards,
Bryan Ackerly
On 07/04/2013, at 4:19 AM, "Lee " <leeritchey@xxxxxxxxxxxxx> wrote:
> Todd,
>
> Thanks for reiterating the need to avoid cutting up ground planes. I am
> puzzled as to why anyone would recommend such a tactic. But, then, there are
> a host of such "off the cuff" things that get circulated year after year
> without any proof they are valid. Even more puzzling is why engineers
> accept such claims without supporting evidence that they are valid.
>
> They keep me very busy most of the time fixing problems that they cause!
>
> -----Original Message-----
> From: Todd Hubing
> Sent: Saturday, April 06, 2013 10:54 AM
> To: <si-list@xxxxxxxxxxxxx>
> Subject: [SI-LIST] Re: Ethernet emissions.
>
> Bryan,
>
>
> Please don't cut up your ground. I wouldn't want anyone on this list to get
> the idea that isolating grounds is going to solve a radiated emissions
> problem above 100 MHz. From the symptoms and the measurements you describe,
> it appears that you are driving the cable relative to your circuit board
> ground with a CM voltage produced directly by the PHY and insufficiently
> attenuated by the connector magnetics. If you've maintained balance in your
> layout between the PHY and the connector, you may need to consider using a
> different connector with better CM rejection.
>
>
>
> At these frequencies, nothing you do with your ground is going to improve
> upon the solid plane that you currently have. Trying to establish separate
> grounds that are at different potentials is likely to make things worse.
>
>
>
> Todd
>
> -----
>
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