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

About this list Date view Thread view Subject view Author view

From: Ron Miller (rmiller@Brocade.COM)
Date: Thu May 11 2000 - 19:39:41 PDT


Hi Bob

Good point.

However, if this is from a digital signal, confining the energy to the
inside
of the board raises its voltage until the dissipation of the material itself
reaches an equilibrium.

Also, you may note that higher order harmonics get bigger and with their
shorter wavelength find escape paths.
ron miller

> -----Original Message-----
> From: Bob Davis
> Sent: Wednesday, May 10, 2000 11:31 PM
> To: si-list@silab.eng.sun.com
> Cc: Patrick Davis
> Subject: RE: [SI-LIST] : May 9th Presentation: "Radiation from Edge
> Effects in Printe...
>
> Peter Arnold summarized the meeting in a few words.
>
> I think it boils down to conservation of energy. Once energy is injected
> into the board structure, it will necessarily leave as some form of
> energy.
> The best way is not to inject as much in the first place, energy birth
> control, and to transform the remaining RF energy into heat or other
> energy
> form that does not approach detection levels on the 10 meter site.
>
> Cheers
> Bob Davis
>
> -----Original Message-----
> From: owner-si-list@silab.eng.sun.com
> [mailto:owner-si-list@silab.eng.sun.com]On Behalf Of ARNOLD,PETER
> (HP-Cupertino,ex3)
> Sent: Wednesday, May 10, 2000 9:39 AM
> To: 'si-list@silab.eng.sun.com'
> Subject: RE: [SI-LIST] : May 9th Presentation: "Radiation from Edge
> Effects in Printe...
>
>
> Doug,
>
> Here is what I think I heard at the EMC society presentation. The
> simulations presented showed that 20H structures they examined actually
> resulted in more emission at the board edge. However, the presenters were
> neutral on whether this was detrimental to compliance for the system as a
> whole, pointing out that EMC solutions are rarely universally applicable.
> I
> hope they post this on the web, I found it most instructive.
>
> The main points I remember:
>
> 1) Time-varying currents on vias can inject radial TEM-mode waves into the
> space between planes.
>
> 2) The energy thus injected bounces around the cavity volume between the
> planes. The board edge is a discontinuity in the medium and so results in
> partial reflection of the propagating wave and partial transmission, i.e.
> radiation from the board edge.
>
> 3) Fencing the board edge with grounded vias is equivalent to changing the
> PCB-edge discontinuity to a short to ground, so the reflection coefficient
> becomes -1 and all energy is kept inside of the fenced area.
>
> 4) By contrast, a 20H-rule example showed that that structure, which looks
> a
> little like a patch antenna, allows for more efficient radiation from the
> edge. The exposed area allows a propagation mode where energy can travel
> around the outside edges of the board also. Thus less energy is trapped
> within the board area and more gets radiated.
>
> 5) Is this good? Energy bouncing around between planes can be picked up by
> structures like the one that initially injected it, e.g. vias, and then
> travel along conductors to outside surface components where it can be
> emitted. This is not especially desirable. On the other hand, the more
> efficient radiatiing edge (20H) puts more energy into the system chassis,
> which moves the problem one level higher.
>
> 6) Closely spaced ground vias all across the board had the effect of
> fencing
> in the injected energy to a small area. This seems to cut radiation from
> the
> edges drastically. I would like to know more about this particular case.
>
> The data was obtained from an FDTD simulation of a small board with a
> single
> off-center via as the point of injection. Excitation was with both a
> continuous sine-wave at 1GHz and also a Gaussian-derivative pulse.
> Dielectric losses were included in the FR4 model. The results of lengthy
> simulations were presented as captivating animations, with color variation
> showing the magnitude of the Poynting vector across the whole board. The
> test setup was of necessity rather artificial but it did help to give a
> feel
> for the physical behavior underlying radiation from board edges.
>
> peter.
>
> -----Original Message-----
> From: Doug McKean [mailto:dmckean@corp.auspex.com]
> Sent: Tuesday, May 09, 2000 3:27 PM
> To: si-list@silab.eng.sun.com
> Subject: Re: [SI-LIST] : May 9th Presentation: "Radiation from Edge
> Effects in Printe...
>
>
> I won't be able to make the meeting.
> Any chances of having what's presented
> put up on a website? - Doug
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
> majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
> si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> si-list archives are accessible at http://www.qsl.net/wb6tpu
> ****
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
> majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
> si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> si-list archives are accessible at http://www.qsl.net/wb6tpu
> ****
>
>
>
> **** To unsubscribe from si-list or si-list-digest: send e-mail to
> majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
> si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
> si-list archives are accessible at http://www.qsl.net/wb6tpu
> ****
>

**** To unsubscribe from si-list or si-list-digest: send e-mail to
majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
****


About this list Date view Thread view Subject view Author view

This archive was generated by hypermail 2b29 : Wed Nov 22 2000 - 10:50:18 PST