Muriel, I applaud your tenacity in trying to achieve an understanding of the common-mode current mechanism.
"Common-mode" currents in printed circuit board structures are usually the result of an asymmetry. These asymmetries do not appear in circuit schematic diagrams, so they can be difficult to simulate. These asymmetries are usually directly related to geometrical features of the circuit, PCB and/or chassis. References to assist your understanding are: 1. J.L. Drewniak, T. Hubing, and T. Van Doren, "Investigation of Fundamental Mechanisms of Common-Mode Radiation from Printed Circuit Boards with Attached Cables," 1994 IEEE EMC Symposium Record, pp. 110-115. 2. There is a more recent and complete article in the IEEE transactions on EMC , but I do not have the complete reference citation. The title is probably the same as seen above, but the principal author is D. Hockanson and the article is more recent than 1996. (If you are truly interested, I can give you Hockanson's e-mail address offline and you can get the correct reference citation from him.) These articles describe the fundamental mechanisms formed by geometrical asymmetries in PCB circuits that can cause "commom-mode" radiation. Other articles appear in the IEEE EMC Symposium Records by F. Leferink. Leferink's articles may be more difficult to read and do not always corroborate the findings of the above two references. I recommend you start with the two above and read Leferink's afterward. Jim Knighten ________________________________________________________ Dr. Jim Knighten e-mail: jim.knigh...@ncr.com <jim.knigh...@ncr.com> Technical Consultant - Design NCR 17095 Via del Campo San Diego, CA 92127 http://www.ncr.com <http://www.ncr.com> Tel: 858-485-2537 Fax: 858-485-3788 -----Original Message----- From: Muriel Bittencourt de Liz [mailto:mur...@grucad.ufsc.br] Sent: Thursday, May 04, 2000 8:13 AM To: EMC-PSTC List Subject: Re: origin of common-mode currents Group, Thanks for all the answers to the question of common-mode emissions. But, as I did once, most of you didn't understand what I meant. I've already read books of EMC (like C.R. Paul), saw a lot of homepages/magazines (RBItem, chapters of IEEE EMC society), read books of electronics-area... etc... But all this references did not mention anything about the physical phenomena of the common-mode emissions. I don't know if I'm not being clear... So, please question me about more details... For example, in a simple circuit (a DC battery feeding a resistor), do I have common-mode emissions? Are the common-mode emissions inherent from any physical system? Can I model them in HF? Thanks in advance. Muriel ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: jim_bac...@mail.monarch.com Michael Garretson: pstc_ad...@garretson.org For policy questions, send mail to: Richard Nute: ri...@ieee.org
