[SI-LIST] Re: the effect of box on EMI
- From: "Moustapha Abdi Hassan" <mahassan@xxxxxxxxxxxx>
- To: "Grasso, Charles" <Charles.Grasso@xxxxxxxxxxxx>, "zhangkun 29902" <zhang_kun@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 29 Jul 2008 16:01:44 -0400
Henry Ott. Wrote an article about dipole antenna and explains the effect
of providing a metal chassis to a PCB:
http://www.hottconsultants.com/pdf_files/dipoles-2.PDF
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Grasso, Charles
Sent: Tuesday, July 29, 2008 2:45 PM
To: zhangkun 29902; si-list@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: the effect of box on EMI
Hello Zhangkun,
Assuming that you are using a simple plate under the board and
not a box (as mentioned in your subject line), then the effect you are
noticing is cancellation of common-mode currents in the plate. The
plate in this case acts as an image plane. The bigger the plate the
more effect it has.
Chas
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of zhangkun 29902
Sent: Tuesday, July 29, 2008 8:41 AM
To: si-list@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] the effect of box on EMI
Dear all
In the recent test, I found out that the effect of metal plane on EMI is
obviously.
Details:
There is a product with only one PCB of 4 layer. The EMI of the PCB is
measured at first. Then the PCB is put on a metal plane. The EMI is
lessen very much(>6db).
What is the theory of this case? The second and more important question
is how to apply the effct of the metal plane by means of modification of
the PCB, while without additional cost.
Best Regards
Zhangkun
2008.7.29
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