[SI-LIST] Re: Paper reference to download

  • From: "Grasso, Charles" <Charles.Grasso@xxxxxxxxxxxx>
  • To: "'leeritchey@xxxxxxxxxxxxx'" <leeritchey@xxxxxxxxxxxxx>,'Charles Grasso' <cgrassosprint1@xxxxxxxxxxxxx>,'Larry Barnes' <larry.barnes@xxxxxxxxxx>,"'si-list@xxxxxxxxxxxxx'" <si-list@xxxxxxxxxxxxx>
  • Date: Mon, 20 Oct 2003 15:38:02 -0600

Hi Lee,

The paper I was referring to was: 
New techniques for reducing printed circuit board common-mode radiation 
By Dockey, R.W.; German, R.F.; This paper appears in: Electromagnetic
Compatibility, 1993. Symposium Record. 1993 IEEE International Symposium on
Page(s): 334 - 339 Volume:9-
Issue: 13 Aug 1993

We were indeed comparing different papers..

Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel:  303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Email: charles.grasso@xxxxxxxxxxxx;  
Email Alternate: chasgrasso@xxxxxxxx
 


-----Original Message-----
From: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx] 
Sent: Monday, October 20, 2003 10:26 AM
To: Charles Grasso; Larry Barnes; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: Traces don't cause EMI - really?


Charles,

The document I have, the one sited by Larry, FIgure 4 is a placement of
antennas.  What document do you have?  The conclusion in the document I have
makes no such statements.

Lee 


> [Original Message]
> From: Charles Grasso <cgrassosprint1@xxxxxxxxxxxxx>
> To: <leeritchey@xxxxxxxxxxxxx>; Larry Barnes 
> <larry.barnes@xxxxxxxxxx>;
<si-list@xxxxxxxxxxxxx>
> Date: 10/19/2003 7:21:16 PM
> Subject: RE: [SI-LIST] Re: Traces don't cause EMI - really?
>
> Lee I am astounded at your comments. If you would glance at Figure 4 
> (Emissions from a reference PCB without cables) you will see that the 
> Y-axis is numbered and (although not listed) is intended to be in 
> dBuV. If you look at the FCC Class B limit (superimposed on the
> graph) I think you'll agree that the reference board actually FAILED 
> Class B at around 300MHz. I'd say that was pretty significant. So, 
> again, you are wrong to assert that the detected emissons are not 
> large enough to cause concern.
>
> I have modeled this board in Ansoft HFSS and got the same results.
>
> Did you read the Conclusion?
>
> CONCLUSION: A multilayer PCB with a solid ground plane produced 
> radiated emissions similar to a dipole antenna. SO Traces over planes 
> DO cause emissions. The emissions are from the PCB/trace structure.
> Change the dimensions, add cables and the profile changes.
>
> Counter-challange - Prove to me that traces DO NOT radiate.
>
>
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx 
> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Lee Ritchey
> Sent: Sunday, October 19, 2003 5:06 PM
> To: Larry Barnes; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Traces don't cause EMI - really?
>
>
> I downloaded a copy of this paper a few minutes ago.  The conclusions 
> of the paper do not state that microstrip traces emit significant EMI.  
> All that is stated is that the analysis and chamber measurements agree 
> within measurement accuracy of what little energy is detected.  The 
> actual amount is not stated in the paper.  There is certainly no claim 
> that the detected emissions are large enough to cause concern among 
> EMC engineers.
>
> This is likely one of those cases where the difference is between 
> detectable and significant.  There is no claim in this paper that the 
> emissions are significant, only detectable.
>
> If we are to accept that surface traces are significant sources of 
> EMI, there needs to be credible demonstration of this.  The reason is,
designers
> are expected to expend cost avoiding microstrip traces.  To do this, 
> there needs to be demonstrated emissions that are worth the extra cost 
> to
control.
>
> My challenge to the proponents of this claim is to provide this 
> demonstration.
>
> I and many others have designed hundreds, maybe thousands of PCBs with 
> traces on outer layers with all the products successfully passing all 
> emissions tests.  That could not happen if these claims are true.
>
> Lee
>
>
> > [Original Message]
> > From: Larry Barnes <larry.barnes@xxxxxxxxxx>
> > To: <si-list@xxxxxxxxxxxxx>
> > Date: 10/18/2003 5:42:14 AM
> > Subject: [SI-LIST] Re: Traces don't cause EMI - really?
> >
> > I just couldn't resist after all this discussion.  I would refer you 
> > to
=
> > a study done by Dr. Dave Hill of NIST.  I demonstrates that 
> > microstrips
=
> > indeed radiate.  The title of the paper is "Radiated Emissions and = 
> > Immunity of Microstrip Transmission Lines: Theory and Reverberation 
> > = Chamber Measurements"  IEEE Trans on EMC  May 1996.=20
> >
> > Larry
> >
> >
>
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
> > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
> > Lawrence C. Barnes
> > QLogic Corporation
> > Aliso Viejo, CA  92656
> >
> >
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>
>
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