Hi Doug,
You might note that Franz uses a near-field probe which will be sensitive to
a different phenomenon than what you're referring to.
Jeff Loyer
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
Behalf Of Doug Smith
Sent: Tuesday, July 5, 2016 2:22 PM
To: curtmcn@xxxxxxxxx; si-list@xxxxxxxxxxxxx; LeeRitchey; Grasso, Charles
Subject: [SI-LIST] Re: Via fence along board edge
Hi Chas,
That seems to indicate problems well under the waveguide cutoff frequency.
Thanks.
Doug
On Tue, 5 Jul 2016 21:17:58 +0000, "Grasso, Charles"
<Charles.Grasso@xxxxxxxxxxxx> wrote:
Hah - at last! Simple language for the "restofus". :-)
Doug - Franz Gisins paper shows resonances well below 500GHz!!
Best Regards
Charles 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: Doug Smith [mailto:doug@xxxxxxxxxx] Sent: Tuesday, July 05,
2016 3:07 PM
To: Grasso, Charles; curtmcn@xxxxxxxxx; si-list@xxxxxxxxxxxxx; Lee
Ritchey
Subject: RE: [SI-LIST] Re: Via fence along board edge
Hi Lee,
It does not matter if the problem is made up. In this case, I want to
show that an open side of a PCB is much like an open wave guide, but
the the dimensions are so small that the interesting frequencies are
high enough as not to be a problem. This puts the argument about PCBs
into very simple language and that satisfies engineering curiosity.
Citing lots of data does not lead to an understanding of the overall
principle, which is what I am getting at.
So, I think the two cases are the same and was looking for your
insight. I have done the calculations, and making reasonable
assumptions on the dimensions, I get frequencies over 500 GHz where
edge radiation as from a waveguide would happen! Just wondering if I
did this correctly. Doug
On Tue, 5 Jul 2016 13:56:08 -0700, Lee Ritchey
<leeritchey@xxxxxxxxxxxxx> wrote:
This seems to me to be another case of trying to solve an imaginary
problem. >
As a side comment on my posts and the responses to them, I oftensay > that I am from Missouri, and need to be shown that a problem
actually > exists before I attempt to solve it.
of > more than 3000 PCBs, I have not yet seen one of them fail EMI
In almost 50 years of engineering and participating in the design
from > energy leaking out the edges and none of them have had via
fences or > recessing to the 20h rule. So if the problem really
exists, the person > making the claim owes an example of a failure due
to the absence of > via fences.
si-list@xxxxxxxxxxxxx; Lee Ritchey <leeritchey@xxxxxxxxxxxxx>
There is a challenge for you! -----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Doug Smith
Sent: Tuesday, July 5, 2016 1:32 PM
To: Charles.Grasso@xxxxxxxxxxxx; curtmcn@xxxxxxxxx; >
Subject: [SI-LIST] Re: Via fence along board edgewavelength > (at some very high
Lee, a question. If the spacing between two planes was 1/2
frequency) would not the edge of the board be a little like an openfew > years. Doug
waveguide? Probably not a practical case, at least not for another
<leeritchey@xxxxxxxxxxxxx> wrote:
On Tue, 5 Jul 2016 11:39:53 -0700, Lee Ritchey >
I think I have traced this myth to its origin. It is no more orless > than a
does > > not "leak out" the sides of a PCB to begin with. One of themmyth. >
The following papers all show with laboratory testing that EMI
even >
shows that with or without these "grounding vias" the results arethe > same.
on > > Electromagnetic Radiation From Printed Circuit Boards", UCCircuit > Design. January 1998
Brooks, Douglas. "90 Degree Corners, The Final Turn." Printed
Fang, Jiayuan, et.al., "Effects of 20-H Rule and Shielding Vias
Santa
Cruz, > Publishing date unknown. > >layers, with ground
Chen, Huabo, et.al., "Effects of 20H Rule and Shielding Vias onin > PCBs", UC Santa Cruz EE Department, May 2001. > >
EMI
Hope this helps. >[mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Grasso, Charles
Lee Ritchey
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx >
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 McNamara
Best Regards
Charles 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. > > There are parts and short traces on the outside
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
pours. > The next layer in is ground on both top and bottom. >//www.freelists.org/archives/si-list
Will the ground fence always help with EMC?will > come out any opening it can find?
- Or sometimes help because that energy has to go somewhere and
wavelength?
- Or mostly help because those openings are small compared to the
Curt
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