[SI-LIST] Re: EMI simulation tools at PCB level
- From: Ron Matthews <rmatthews@xxxxxxxxxx>
- To: Chris.Cheng@xxxxxxxxxxxx, 'Charles Grasso ' <cgrassosprint1@xxxxxxxxxxxxx>, Chris Cheng <Chris.Cheng@xxxxxxxxxxxx>, "'zhang_kun@xxxxxxxxxx '" <zhang_kun@xxxxxxxxxx>, "'si-list@xxxxxxxxxxxxx '" <si-list@xxxxxxxxxxxxx>
- Date: Fri, 03 Dec 2004 09:06:08 -0500
Chris,
This is one of those areas where you'll probably never be able to
remove the human from the simulation in order to get meaningful results.
Since the radiated emissions profile of a PCB is heavily dependent on the
immediate operational environment (i.e. the enclosure, cable, etc.) it's
not really meaningful to have a program automatically predict what the EMI
levels are going to be. Bear in mind that, like SI, EMI is not just one
phenomenon. Rather, it's a host of different electrical and EM phenomena,
any one of which can cause you EMI problems. I agree with Charles that
consulting an experienced EMC engineer during the early phase of a board's
design is the best way to manage EMI-related risk.
Regards,
Ron Matthews
Principal MTS
Signal Integrity/EMI
Charles Stark Draper Laboratory
555 Technology Square
Cambridge, MA 02139
Voice: 617-258-2519
At 11:12 PM 12/2/2004 -0800, Chris Cheng wrote:
>You mean the =22 part ? :-D
>
>Seriously, I know it is understandable and explainable but I want it to be
>automatically predicted and simulated by a tool. It is easy to fix and patch
>after the fact but I have yet to see a tool to tell me ahead of time the db
>and peaks location. A bare PCB with a few "experimental traces" as in some
>EMI papers, sure. A multi-boards system with chassis and spaghetti cables
>come out ? Show me the money.
>
>-----Original Message-----
>From: Charles Grasso
>To: Chris.Cheng@xxxxxxxxxxxx; zhang_kun@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
>Sent: 12/2/2004 10:31 PM
>Subject: RE: [SI-LIST] Re: EMI simulation tools at PCB level
>
>Chris - It would be *much* easier for you to contact some experienced
>EMC
>engineers - the phenomena you describe are understandabe and
>explainable.
>
>-----Original Message-----
>From: si-list-bounce@xxxxxxxxxxxxx
>[mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Chris Cheng
>Sent: Thursday, December 02, 2004 5:13 PM
>To: 'zhang_kun@xxxxxxxxxx'; si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: EMI simulation tools at PCB level
>
>
>I am sure the consumer product guys will laugh at my stupidity but I can
>never design a PCB that will pass FCC B without a large metal cage
>chassis.
>I've always wanted to simulate why if I tighten the screw by one more
>turn
>on my door and my EMI gaskets compressed a little harder and the
>signature
>changed by 10 db. Or if I hang the cable this way or that way the
>signature
>changed by a few db. What I am trying to say is while EMI from PCB may
>be
>the source, the enclosure/environment the PCB is in seems to have a
>bigger
>impact on whether you are passing FCC than the PCB itself. Granted this
>is
>just from an incompetent designer like me who cannot ship an absolute
>clean
>PCB that can be wrapped in a plastic bag and passing FCC. Any simulation
>tools that can help me ?
>
>ps Is there any way I can receive messages from the list from outside
>the US
>without these =2 =22 ? I know the US or English language is not the
>center
>of the Universe so I appolgize in advanced.
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