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

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From: Chris Rokusek (crokusek@innoveda.com)
Date: Tue May 09 2000 - 16:42:47 PDT


Jim,

Aahh-- the old put your money where your mouth is! I see what happens when
I post too often in one week!

Can't be 100% sure but its not likely at this time since we're currently
committed to supporting University of Missouri-Rolla for their excellent EMI
research.

Perhaps a company with a much higher P/E would be interested ;) !

Chris Rokusek
Innoveda

> -----Original Message-----
> From: owner-si-list@silab.eng.sun.com
> [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Jim Freeman
> Sent: Tuesday, May 09, 2000 12:18 PM
> To: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : May 9th Presentation: "Radiation from Edge
> Effects in Printe...
>
>
> Hi,
> Would Innoveda be interested in funding such a project and
> providing lab
> space for the effort.
>
> Thanks
> Jim Freeman
>
> Chris Rokusek wrote:
>
> > Mike,
> >
> > My interest in the 20H rule is to understand the mechanisms involved. I
> > would like to quantify how well the 20H rule is able to reduce surface
> > currents. I would like to quantify the magnitude of these
> surface currents
> > with and without the 20H rule and compare. I would like to know what
> > magnitude source is required to generate what magnitude surface
> currents. I
> > would like understand the 20H rule's effects with and without other
> > conductors on the board besides the planes. I would like to
> know whether
> > the coupling to surface parts is capacitive or inductive or
> both. I would
> > like to compare different stackups...
> >
> > Answers to these questions may allow better design techniques. Better
> > decoupling can limit the source across the planes to safe
> level. Knowing
> > the distribution of surface current can aid placement/routing.
> Knowing the
> > coupling mechanisms can aid in placement/routiing. How can a
> board designer
> > make tradeoffs among all the various design techniques
> (Timing/EMI/SI/etc.)
> > without knowing the limits of each?
> >
> > Honestly I don't expect the answers to these tough questions to
> be posted on
> > this list (great surprise if they would), but perhaps these
> SI-List threads
> > will encourage a thesis or two and we can all catch the results
> at the next
> > EMC Symposium.
> >
> > Knowledge is ultimate. Keep it coming!
> >
> > Chris Rokusek
> > Innoveda
> >
> > > -----Original Message-----
> > > From: owner-si-list@silab.eng.sun.com
> > > [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of MikonCons@aol.com
> > > Sent: Monday, May 08, 2000 4:52 PM
> > > To: si-list@silab.eng.sun.com
> > > Subject: Re: [SI-LIST] : May 9th Presentation: "Radiation from Edge
> > > Effects in Printe...
> > >
> > >
> > > 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.
> > >
> > > The 20H rule had nothing to do with suppressing this radiation.
> > > The moral?
> > > Avoid inducing surface currents any way you can.
> > >
> > > Mike
> > >
> > > Michael L. Conn
> > > Owner/Principal Consultant
> > > Mikon Consulting
> > >
> > > *** Serving Your Needs with Technical Excellence ***
> > >
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