Hi Group. I'm a first time poster. An interesting discussion! I remember doing some research 10 years ago in a previous employment looking at the radiated emissions from pre-fabricated Printed Circuit Boards with and without (floating) groundplanes. Dimensions of the board were around 15cm by 10cm with simple trace configurations (go and return) to a battery. The (common mode CM) radiated emissions between 30MHz and 1GHz were greatly reduced with the floating groundplane in place. This is due to the image of the CM current in antiphase causing the far field cancellation. I assume a similar principle would apply to ribbon cable with a floating shield assuming good coverage? This point does not consider low frequency magnetic field.
Regards Adam Bullivant. From: [email protected] [mailto:[email protected]]On Behalf Of John Woodgate Sent: 16 September 2005 14:10 To: [email protected] Subject: Re: When is a cable shield not a cable shield? Ken Javor <[email protected]> wrote (in <bf4f5626.2c1f5%[email protected]>) about 'When is a cable shield not a cable shield?', on Thu, 15 Sep 2005: > The reason for terminating the shield at both ends at high frequencies >(cable electrically long) is to contain the eddy currents on the >interior of the equipment enclosure, of which the shield is an >extension, just as a tunnel or skyway between two buildings becomes an >extension of the buildings it connects. It's better to keep the eddy currents to the OUTSIDE of the enclosure, because if they flow on the inside, they can radiate into internal circuits. This can be achieved by using metal-shelled free connectors with 306 degree contact with both the cable shield and the shell of the mating fixed connector which is attached to the outer (conducting) surface of the enclosure. -- Regards, John Woodgate, OOO - Own Opinions Only. Deadlines are 90% of deadliness. http://www.jmwa.demon.co.uk Also see http://www.isce.org.uk - 2005 IEEE Symposium on Product Safety Engineering 3-4 October Schaumburg, IL http://www.ieee-pses.org/symposium This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [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.ieeecommunities.org/emc-pstc - 2005 IEEE Symposium on Product Safety Engineering 3-4 October Schaumburg, IL http://www.ieee-pses.org/symposium This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. Website: http://www.ieee-pses.org/ To post a message to the list, send your e-mail to [email protected] Instructions: http://listserv.ieee.org/listserv/request/user-guide.html List rules: http://www.ieee-pses.org/listrules.html For help, send mail to the list administrators: Scott Douglas [email protected] Mike Cantwell [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.ieeecommunities.org/emc-pstc
