[SI-LIST] 答复: the effect of box on EMI
- From: Zhangkun <zhang_kun@xxxxxxxxxx>
- To: "'Grasso, Charles'" <Charles.Grasso@xxxxxxxxxxxx>, si-list@xxxxxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Wed, 30 Jul 2008 18:58:17 +0800
Hi Chas
OK. The first question has been answered.
How about the second question? "how to apply the effct of the metal plane
by means of modification of the PCB, while without additional cost."
As we know, the simple plate under the board could cancel the common-mode
currents. What is the source of the common mode current and how to cancel it
by means of PCB design. For example, adding decoupling caps?
Best Regards
Zhangkun
2008.7.30
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-----邮件原件-----
发件人: Grasso, Charles [mailto:Charles.Grasso@xxxxxxxxxxxx]
发送时间: 2008年7月30日 2:45
收件人: zhangkun 29902; si-list@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx
主题: RE: [SI-LIST] 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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