Ken, I was impressed by a paper:
"Common mode current induced on wires attached to multilayer printed wire boards with segmented ground planes," by EMC lab of Univ. of Missouri-Rolla, pp. 116-120, 1994 IEEE EMC Symposium. That was the first article, to my knowledge, for EMC design community to investigate the correlation between CM current on attached cables and PCB layout design both theoretically and experimentally. It deserves being called a milestone, although some EMC design engineers had kind of feelings before the article and the theoretical calculation used by EMC lab of UMR at that time was a rough approximation. Once common mode voltage is established in either ground or power planes, the RF potential would find efficient way to radiate RF energy toward outside space. That is another type of RF loop for CM current to implement its mission :-). Attached cables are good wire antennas. Any traces connected to gnd/pwr planes of the PCB could also become antennas. Barry Ma [email protected] ------------- On Wed, 03 May 2000, "Ken Javor" wrote: > Lots of books cover this. Clayton Paul comes to mind for signal cable cm > CE, and Mark Nave for power-line cm CE. > > Cable cm CE: > > Usually dm ground bounce on a PCB converting to a cm potential driving cm > currents onto I/O port connected cables. Fixes are better PCB layout, > proper grounding/isolation of I/O port. > > Power-line CM CE: > > Parasitic capacity developed either from switching transistor to chassis > ground and/or across switching transformer primary to secondary. Allows > current to be driven into ground. Fixes include reducing the cm > capacitance, and filtering: Y-caps to force currents to circulate within > EUT, and a cm choke to make Y-caps look like a more attractive path to > ground than through the LISN. > _______________________________________________________________________ Why pay when you don't have to? Get AltaVista Free Internet Access now! http://jump.altavista.com/freeaccess4.go _______________________________________________________________________ ------------------------------------------- This message is from the IEEE EMC Society Product Safety Technical Committee emc-pstc discussion list. To cancel your subscription, send mail to: [email protected] with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Jim Bacher: [email protected] Michael Garretson: [email protected] For policy questions, send mail to: Richard Nute: [email protected]
