Hi Lee and the group,
Sometimes thinking about made up examples can be instructive and save a
lot of time. EMC simulation is often about thinking of made up examples
to train one's knowledge as it is not practical to model a real system
of multiple large racks of equipment with a hundred connected cables in
an uncontrolled environment.
Doug
On Tue, 5 Jul 2016 13:37:39 -0700, Lee Ritchey
<leeritchey@xxxxxxxxxxxxx> wrote:
This has all the makings of solving an imaginary problem! Do we have
time for that?
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Ken Wyatt
Sent: Tuesday, July 5, 2016 1:23 PM
To: Charles Grasso <Charles.Grasso@xxxxxxxxxxxx>
Cc: Lee Ritchey <leeritchey@xxxxxxxxxxxxx>; curtmcn@xxxxxxxxx;
si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Via fence along board edge
If EM waves indeed propagate through the dielectric, what’s to
stop them from radiating out the edges of a PC board? This assumes,
of course, that there are discontinuities or impedance mismatches
that can cause reflections.
Cheers, Ken
_______________________
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On Jul 5, 2016, at 1:31 PM, Grasso, Charles<Charles.Grasso@xxxxxxxxxxxx> wrote:
Caused by > Radially Propagating Waves Inside High Speed DigitalSorry - One last thing: I would refer you to Minimizing EMI
Logic PCBs - Franz Gisin and Zorica Pantic Tanner.
less than a myth.Best RegardsCharles Grasso
Compliance Engineer
Echostar Communications
(w) 303-706-5467
(c) 303-204-2974
(t) 3032042974@xxxxxxxxx
(e) charles.grasso@xxxxxxxxxxxx
(e2) chasgrasso@xxxxxxxxx
From: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx]-----Original Message-----
Sent: Tuesday, July 05, 2016 12:40 PM
To: Grasso, Charles; curtmcn@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: RE: [SI-LIST] Re: Via fence along board edge
I think I have traced this myth to its origin. It is no more or
does not "leak out" the sides of a PCB to begin with. One of themThe following papers all show with laboratory testing that EMI
even shows that with or without these "grounding vias" the results
are the same.
Circuit > Design. January 1998Brooks, Douglas. "90 Degree Corners, The Final Turn." Printed
on Electromagnetic Radiation From Printed Circuit Boards", UC SantaFang, Jiayuan, et.al., "Effects of 20-H Rule and Shielding Vias
Cruz, Publishing date unknown.
EMI in PCBs", UC Santa Cruz EE Department, May 2001.Chen, Huabo, et.al., "Effects of 20H Rule and Shielding Vias on
[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Grasso, CharlesHope this helps.From: si-list-bounce@xxxxxxxxxxxxx >
Lee Ritchey
-----Original Message-----
Sent: Tuesday, July 5, 2016 9:21 AMdon't have a simulation tool or handy dandy formula to "guess" if
To: curtmcn@xxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Via fence along board edge
If there is a concern about cavity resonances causing EMI and you
there will be an interference problem or not then a via fence is a
good way to sleep at night! > > (Just count vias instead of sheep
..one..two...three...zzzzzzz)
[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Curt McNamaraBest RegardsCharles Grasso
Compliance Engineer
Echostar Communications
(w) 303-706-5467
(c) 303-204-2974
(t) 3032042974@xxxxxxxxx
(e) charles.grasso@xxxxxxxxxxxx
(e2) chasgrasso@xxxxxxxxx
-----Original Message-----From: si-list-bounce@xxxxxxxxxxxxx >
Sent: Tuesday, July 05, 2016 6:51 AMinside the PCB.
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Via fence along board edge
I have seen this done, and understand the desire to trap EM waves
There are parts and short traces on the outside layers, with ground pours.will come out any opening it can find?
The next layer in is ground on both top and bottom.
Will the ground fence always help with EMC?
- Or sometimes help because that energy has to go somewhere and
wavelength?- Or mostly help because those openings are small compared to the
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