Hi The following article "Boxing Clever" should make interesting reading on this subject. http://www.compliance-club.com/article.php?sid=16&mode=&order=0 Cheers Alan E Hutley EMC Compliance Journal ----- Original Message ----- From: <[email protected]> To: <[email protected]> Sent: Wednesday, June 06, 2001 5:35 PM Subject: RE: Shielding Effectiveness Question
> > There's an article by B. Archambeault and C. Brench, entitled, "Shielded Air > Vent Design Guidelines from EMI Modeling" in IEEE Int. Symp. On EMC, Dallas > Tex., Aug. 1993, p.195. > > This article is referenced in a 1994 IEEE article entitled: "Modeling > Leakage Through Finite Apertures with TLM by Clifford H. Draft. > > Max Kelson > Evans & Sutherland > > > -----Original Message----- > From: Brench, Colin [mailto:[email protected]] > Sent: Wednesday, June 06, 2001 5:36 AM > To: Neven Pischl; [email protected]; > [email protected] > Subject: RE: Shielding Effectiveness Question > > > Greetings Neven, > > There are a couple of things that need to be considered when > you have an > rf source close to a shield with apertures. First is the > "shielding" > properties of the shield as people have said this is very > dependent upon > the field impedance when you are in the near field. Second > and no less > important is the direct coupling between the shield and > source > conductors, the presence of the shield greatly affects the > properties of > the radiating source. > > With everything so close together there could well be > resonances which > result in windows in the shield at lower frequencies than > you would > expect. Some years ago I published a paper with my wife > (Colin and > Bronwyn Brench) on the effects of conductors close to > apertures in a > shield which illustrates this effect. The paper used very > simple > geometries not real ones and used a field source not a local > one - but > the premise was the same. It can be found in the EMC > Symposium record - > sorry I don't know what year - it won't help you directly, > only show > what behavior you might expect. I believe that to get an > answer to your > question you can only go so far analytically and that to get > a detailed > answer you will have to resort to a computational > electromagnetics tool. > > It is important to accurately represent your EMI source, > physically and > electrically (I.e. source impedance) to get accurate > results. > > good luck with this, > > Colin. > > > -----Original Message----- > From: Neven Pischl [mailto:[email protected]] > Sent: Tuesday, June 05, 2001 12:16 PM > To: [email protected]; [email protected] > Subject: Shielding Effectivness Question > > > I would appreciate if anyone could let me know if there are > any > references (books, application notes, anythig ..) that deal > with > shielding efectivness in cases when a source is close to an > (electrically small) opening in a shield (enclosure). In > such a > situation, the field will penetrate through the hole and > leak even if > the size is much smaller than the wavelength. I am > particularly > interested in situation when high-frequency source, such as > a PCB edge > or a component operating at (say) 1 GHz and above is in > proximity of the > venting holes, "small" gaps in the chassis etc. > > All references that I have deal with uniform plane wave > propagating > incident to a metal plane with a slot or hole, in which case > it is > enought o have electrically small size of the opening (e.g. > lambda/10) > to efficiently block any field propagation through the > barrier. I can't > find any useful reference that deals in any analytical way > with the > situation I am intersted in. > > I believe I might get some answers using some of the > simulation > programs, but at the moment I am more intersted in the > analysis of the > problem than in simulating it. > > Thank you, > > Neven Pischl > > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: > http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: [email protected] > Dave Heald [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web > at: > http://www.rcic.com/ click on "Virtual Conference > Hall," > > ------------------------------------------- > This message is from the IEEE EMC Society Product Safety > Technical Committee emc-pstc discussion list. > > Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ > > To cancel your subscription, send mail to: > [email protected] > with the single line: > unsubscribe emc-pstc > > For help, send mail to the list administrators: > Michael Garretson: [email protected] > Dave Heald [email protected] > > For policy questions, send mail to: > Richard Nute: [email protected] > Jim Bacher: [email protected] > > All emc-pstc postings are archived and searchable on the web at: > http://www.rcic.com/ click on "Virtual Conference Hall," > ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. Visit our web site at: http://www.ewh.ieee.org/soc/emcs/pstc/ To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Michael Garretson: [email protected] Dave Heald [email protected] For policy questions, send mail to: Richard Nute: [email protected] Jim Bacher: [email protected] All emc-pstc postings are archived and searchable on the web at: http://www.rcic.com/ click on "Virtual Conference Hall,"
