Re: [SI-LIST] : May 9th Presentation: "Radiation from EdgeEffects in Printe...

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From: Doug McKean (dmckean@corp.auspex.com)
Date: Tue May 09 2000 - 15:23:35 PDT


Sorry guys, I'm totally lost.

How does any of this have anything to do with
the issue of cutting the power plane back 20H
from the edge of the ground plane? - Doug

sweir wrote:
>
> Didn't that open the circuit at the source and prevent the stub from radiating?
> At 09:08 AM 5/9/00 -0400, you wrote:
> > >
> > > Chris R.:
> > >
> > > One exemplary case I recently came across had a series-terminated clock
> > line
> > > that was immediately submerged to a stripline which went to a connector on
> > > the edge of a PCB. The optional card that would use the connector was NOT
> > > installed. The connector receptacle pin rose above the PCB about 3/16
> > inch.
> > > This small 3/16-inch stub coupled harmonic energy to the SURFACE of the
> > PCB
> > > (a ground plane) at the SURFACE resonant frequency of the PCB. Surface
> > > currents could be measured all over the surface ground plane (with a small
> > > Fischer Communications probe). NASTY radiation resulted.
> > >
> > > Simple removal of the series termination resistor at the clock driver end
> > > reduced system radiation over 30 dB.
> >-----------------------------------------
> >How do you explain this significant reduction in emission levels by
> >the simple removal of the series termination resistor?
> >-----------------------------------------

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