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 > > > ------------------------------------------------------------------ > To unsubscribe from si-list: > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field > > or to administer your membership from a web page, go to: > //www.freelists.org/webpage/si-list > > For help: > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field > > List archives are viewable at: > //www.freelists.org/archives/si-list > or at our remote archives: > http://groups.yahoo.com/group/si-list/messages > Old (prior to June 6, 2001) list archives are viewable at: > http://www.qsl.net/wb6tpu > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu