Hello Deepak, This may have been mentioned before, but here goes: If the magnetics you use for your Ethernet have a centretap on the input side of the transformer (sometimes connected to a voltage rail, sometimes to ground) then you should try filtering the supply to this with an RC or bead-cap filter. I have seen Ethernet radiated emissions fail CISPR 22 limits without this filtering in place. Be aware that changing the centre tap filtering will affect the characteristics of the Ethernet signal and will mean you will need to re test the electrical parameters. Happy hunting, James
________________________________ From: deepak Engineer [mailto:[email protected]] Sent: 30 September 2010 09:19 To: [email protected] Subject: Re: [PSES] EMI issue with Ethernet Hello Team(Gert,John,Rob,Gary), Thanks for sharing the knowledge/experience... I am still hesitating to take a decision on chassis ground.. On my board, I have four mouting holes for chasis... I cannot use the chassis ground on all four mounting hole, becasue of layout restriction.. Three holes are connected to signal/digital ground while fourth is connector to Ethernet Chassis ground... In whole system, Chasiss ground and signal ground are linked/communicating through only two points.. 1. throught zero ohms resistor between RJ45 jack and signal ground 2. through chassis, where ethernet cable ground will be passed to chassis(thru mounting hole) and mix with singal ground... would it effect the system... is it stable approach.. Cheers, Deepak On 30 September 2010 09:43, John Woodgate <[email protected]> wrote: In message <[email protected]>, dated Thu, 30 Sep 2010, "ce-test, qualified testing bv - Gert Gremmen" <[email protected]> writes: No John, while what you state is correct, the coupling from CM currents out of the ground via the center tap of the transformer is one common way of creating problems. Now I'm completely confused. Earlier in this thread, you wrote: Most of the time the problem is that the ground point center-tap of the Ethernet transformer is insufficiently grounded. Now you seem to be saying that the equipment 'ground' can be a source of CM energy, and I agree it can be. Therefore, it would be better NOT to ground the centre-tap. And much more likely then balancing problems. Balancing problems will immediately be detected by poor transfer rates and errors. CM current will go unnoticed. I don't think so. The balance has to be a long way off before it noticeably affects the signal transfer, but only a little way off to significantly increase emission levels. -- OOO - Own Opinions Only. Try www.jmwa.demon.co.uk <http://www.jmwa.demon.co.uk/> and www.isce.org.uk <http://www.isce.org.uk/> John Woodgate, J M Woodgate and Associates, Rayleigh, Essex UK If at first you don't succeed, delegate. But I support unbloated email http://www.asciiribbon.org/ - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/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: Jim Bacher: <[email protected]> David Heald: <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/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: Jim Bacher <[email protected]> David Heald <[email protected]> - ---------------------------------------------------------------- This message is from the IEEE Product Safety Engineering Society emc-pstc discussion list. To post a message to the list, send your e-mail to <[email protected]> All emc-pstc postings are archived and searchable on the web at http://www.ieeecommunities.org/emc-pstc Graphics (in well-used formats), large files, etc. can be posted to that URL. Website: http://www.ieee-pses.org/ Instructions: http://listserv.ieee.org/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: Jim Bacher <[email protected]> David Heald <[email protected]>
