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

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From: Syed Bokhari ([email protected])
Date: Tue May 09 2000 - 06:08:36 PDT

>
> 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?
-----------------------------------------

> Mike
>
> Michael L. Conn
> Owner/Principal Consultant
> Mikon Consulting
>
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