ethernet radiated emissions- thanks
Dear colleagues; I would like to thank all those who replied to my predicament regarding emissions from an Ethernet port. I have had some first-class advice which will help me solve the problem. Many thanks; Ian McBurney. Allen Heath Limited. email: ian.mcbur...@allen-heath.com ***LEGAL DISCLAIMER: READ THIS FIRST*** This Email and any files transmitted with it are confidential and intended solely for the use of the individual to whom or the entity to which they are addressed. If you have received this email in error please notify the sender immediately. Please note that any views or opinions presented in this email are those of the author and do not necessarily represent those of Allen Heath Limited. This email has been checked for the presence of viruses using Sophos AV Scanner. Anti-virus updates are downloaded on a daily basis . The recipient should also check this email and any attachments for the presence of viruses. Allen Heath Limited accepts no liability for any damage caused by any virus transmitted via this email. *** 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: ethernet radiated emissions
Ian, A signal that strong suggests one possibility to me. It is possible that the board layout was automatically routed. As a result a clock trace was run through the Ethernet magnetics area. This area should be clear of everything but the Ethernet signals. The application notes for the Ethernet interface chipset or magnetics may be of help. If you do find a clock trace routed in this area, try cutting the trace, at both ends, and running a wire on the board and kept away from all I/O ports. You may need to terminate your re-routed clock line. Of course this is only one possibility, but one I have encountered that caused a similar failure. Good luck. Eric Lifsey At 12:17 PM +0100 6/17/05, McBurney, Ian [Allen Heath UK] wrote: Dear colleagues; Can anyone advise me how to reduce the radiated emissions from a 100 base-T Ethernet port with a UTP cable connected to below the EN55022 class B limit? At the moment I am 20dB above the limit at 33MHz. Using STP only reduces the emissions by 6dB. Thanks in advance; Ian McBurney. Allen Heath Limited. email: ian.mcbur...@allen-heath.com 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwellmcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: ethernet radiated emissions
Ian, the question you posted is so generic that nobody can really answer it. It does not give any clue regarding the sources and mechanisms of emission, no results of your troubleshooting, nor does it give any insight into the product and possible causes of the increased emission. If you provide much more details, someone on the reflector might try to help you. Posting the results of your homework would help others help you, and would show that you have done it before asking for help. If you can't, then I believe you might be better off hiring an expert to help you with the problem. STP did not give you much reduction for some or all of the following reasons: 1) The shield is crimped to the shell of the Ethernet plug with only one wire (that's standard), and then the shell makes contact with the shell of the receptacle only with two tabs on its sides. This is far from a good RF 360 deg contact required for good performance of a shield. 2) The location where the shell/shield makes contact with the product is at a considerable RF (ground-noise, i.e. common-mode) potential, so it is driving the shield 3) The shield of the UTP is not really good to start with Regards, Neven -- Original message -- Dear colleagues; Can anyone advise me how to reduce the radiated emissions from a 100 base-T Ethernet port with a UTP cable connected to below the EN55022 class B limit? At the moment I am 20dB above the limit at 33MHz. Using STP only reduces the emissions by 6dB. Thanks in advance; Ian McBurney. Allen Heath Limited. email: ian.mcbur...@allen-heath.com 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: ethernet radiated emissions
Ian, The problem is probably a common-mode signal from some other source using the Ethernet cable as an antenna, as Ken Javor has suggested. The 20dB failure is strong evidence of that because an Ethernet signal based failure would not be that strong. Besides, 33 MHz is not a clock frequency used by 100Base-T, I don’t believe. Attacking the common-mode source on the PCB is the most effective thing to do, as others have suggested. But sometimes this is difficult. As far as STP is concerned, it will do you no good if the board-side connector (jack) is not shielded. Some are not. If the board-side receptacle is shielded, many are configured so that the jack’s shield does not make good contact to the enclosure panel. If it doesn’t, then the effectiveness of the shielding is problematic. If you don’t have a conductive enclosure to connect to, then STP may not help you much with common-mode radiation anyway. Twisted pair Ethernet can be a challenge, but the coaxial version, 10Base-2 was worse. Jim _ James L. Knighten, Ph.D. Teradata, a division of NCR http://www.ncr.com 17095 Via del Campo San Diego, CA 92127 tel: 858-485-2537 fax: 858-485-3788 _ From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org] On Behalf Of Ken Javor Sent: Friday, June 17, 2005 5:30 AM To: McBurney, Ian [Allen Heath UK]; emc-p...@ieee.org Subject: Re: ethernet radiated emissions No experience with Ethernet per se, so this is a very general comment. It sounds as if the emissions are common mode. If so, they may not have anything to do with the Ethernet itself, the Ethernet may be a fortuitous conductor. I would check this using a current probe around the cable, with and without Ethernet traffic. If there is little or no difference, it is ground bounce in the printed circuit board driving conducted emissions onto the Ethernet. Then you have to look at suppressing emissions from that source. From: McBurney, Ian [Allen Heath UK] ian.mcbur...@allen-heath.com List-Post: emc-pstc@listserv.ieee.org Date: Fri, 17 Jun 2005 12:17:17 +0100 To: emc-p...@ieee.org Subject: ethernet radiated emissions Dear colleagues; Can anyone advise me how to reduce the radiated emissions from a 100 base-T Ethernet port with a UTP cable connected to below the EN55022 class B limit? At the moment I am 20dB above the limit at 33MHz. Using STP only reduces the emissions by 6dB. Thanks in advance; Ian McBurney. Allen Heath Limited. email: ian.mcbur...@allen-heath.com 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: ethernet radiated emissions
33MHz - sounds like PCI bus. The radiation originating from Ethernet is very broadband per se as the data is scrambled using a pseudo-random code, thus widening the spectrum. This was intended to reduce EMI. There are several things to think of: - The traces between the magnetics and the connector must be short and well separate from the rest. - Keep the PWB voided of any planes/other signals in this space. - The place under the transformer should be voided as well in order to not compromise the CMR of the transformer. - ... The fact that emission decreases with STP makes me think that there is a connection between the RJ45 socket and the faceplate. SMSC had a nice application note describing ways to avoid common EMI problems with an Ethernet design. The application note is no longer on their website, but I can send it to you if you are interested. Good luck, Michael Michael Nagel Senior EMC Engineer Motorola GmbH ECC Embedded Communications Computing Lilienthalstrasse 15 85579 Neubiberg/Muenchen - Germany Ph: +49-89-9608-0 Fax: +49-89-9608-2376 e-mail: michael.na...@motorola.com info: http://www.motorola.com/computers From: owner-emc-p...@ieee.org [mailto:owner-emc-p...@ieee.org]On Behalf Of McBurney, Ian [Allen Heath UK] Sent: Freitag, 17. Juni 2005 13:17 To: emc-p...@ieee.org Subject: ethernet radiated emissions Dear colleagues; Can anyone advise me how to reduce the radiated emissions from a 100 base-T Ethernet port with a UTP cable connected to below the EN55022 class B limit? At the moment I am 20dB above the limit at 33MHz. Using STP only reduces the emissions by 6dB. Thanks in advance; Ian McBurney. Allen Heath Limited. email: ian.mcbur...@allen-heath.com 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
RE: ethernet radiated emissions
Ian, PCB layout is very critical; especially in the I/O area (around the RJ-45 connectors). Make sure that the Ethernet transformer you use has good common-mode filtering built in. You might also try using Bob Smith termination on the un-used pins of the I/O connector. If you've never heard of Bob Smith termination, do a google search and you can find info about it. App notes from the manufacturer of the Ethernet Phy you're using usually are a good place to start looking for recommendations related to layout. One thing I have found is that if you do use shielded cables make sure you use a cable that has 360 degree connection on the shield. Hopefully some of this helps. I'm no expert but have struggled with these same issues. Bill Fleury From: McBurney, Ian [Allen Heath UK] [mailto:ian.mcbur...@allen-heath.com] Sent: Friday, June 17, 2005 6:17 AM To: emc-p...@ieee.org Subject: ethernet radiated emissions Dear colleagues; Can anyone advise me how to reduce the radiated emissions from a 100 base-T Ethernet port with a UTP cable connected to below the EN55022 class B limit? At the moment I am 20dB above the limit at 33MHz. Using STP only reduces the emissions by 6dB. Thanks in advance; Ian McBurney. Allen Heath Limited. email: ian.mcbur...@allen-heath.com 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: ethernet radiated emissions
No experience with Ethernet per se, so this is a very general comment. It sounds as if the emissions are common mode. If so, they may not have anything to do with the Ethernet itself, the Ethernet may be a fortuitous conductor. I would check this using a current probe around the cable, with and without Ethernet traffic. If there is little or no difference, it is ground bounce in the printed circuit board driving conducted emissions onto the Ethernet. Then you have to look at suppressing emissions from that source. From: McBurney, Ian [Allen Heath UK] ian.mcbur...@allen-heath.com List-Post: emc-pstc@listserv.ieee.org Date: Fri, 17 Jun 2005 12:17:17 +0100 To: emc-p...@ieee.org Subject: ethernet radiated emissions Dear colleagues; Can anyone advise me how to reduce the radiated emissions from a 100 base-T Ethernet port with a UTP cable connected to below the EN55022 class B limit? At the moment I am 20dB above the limit at 33MHz. Using STP only reduces the emissions by 6dB. Thanks in advance; Ian McBurney. Allen Heath Limited. email: ian.mcbur...@allen-heath.com 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
ethernet radiated emissions
Dear colleagues; Can anyone advise me how to reduce the radiated emissions from a 100 base-T Ethernet port with a UTP cable connected to below the EN55022 class B limit? At the moment I am 20dB above the limit at 33MHz. Using STP only reduces the emissions by 6dB. Thanks in advance; Ian McBurney. Allen Heath Limited. email: ian.mcbur...@allen-heath.com 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 emc-p...@ieee.org 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 emcp...@ptcnh.net Mike Cantwell mcantw...@ieee.org For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
Re: Ethernet Radiated Emissions
I read in !emc-pstc that neve...@attbi.com wrote (in 20021011040337.NIT V4193.rwcrmhc51.attbi.com@rwcrwbc69) about 'Ethernet Radiated Emissions' on Fri, 11 Oct 2002: Second, I recommend refraining from sarcastic comments in this forum, since that doesn't seem it was about naivety. No sarcastic comment. I really meant 'naive'. I knew next to nothing about Ethernet before I asked, and now I know a little more. I could not believe that a 100 Mbps system used such long pulses, even for setting up a link. Thank you. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Ethernet Radiated Emissions
Pardon my naivety, but how does '100 Mbit' relate to frequencies of 30 and 60 kHz? Is this 100 Mbit per week? (;-) -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk snip First, a little background on auto negotiation. The IEEE 802.3u 100BaseTX auto negotiation specification uses a modified version of the link integrity test defined for 10BaseT devices. The link integrity test for 10BaseT devices uses the Normal Link Pulse (NLP), a burst pulse every 16 (+/- 8) microseconds. For 10/100 Mbps auto negotiation, a Fast Link Pulse (FLP) is used. The FLP includes the same NLP burst every 16 (+/- 8) msec for backward compatibility plus additional pulses every 62.5 (+/- 7) microseconds. The FLP burst generates code words that are used for compatibility exchanges (duplex settings) between link partners. If a device (such as an Ethernet switch) sends FLP, but only receives NLP from it's link partner (such as a server or workstation), it will stop sending FLP and enable standard 10BaseT operation. I suppose you can figure out that the frequency for 100 Mbps link pulses is 62.5 kHz. If not, calculate 1/16 us. Second, I recommend refraining from sarcastic comments in this forum, since that doesn't seem it was about naivety. I was actually trying to help. Best regards, Neven --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Ethernet Radiated Emissions
[ Neven wrote ] You are seing a spectrum of MLT3 signal, which is 100 Mbit coding. [ John wrote ] Pardon my naivety, but how does '100 Mbit' relate to frequencies of 30 and 60 kHz? Is this 100 Mbit per week? (;-) Could be plenty. I'd guess is something to do with either jitter and/or PLL recovery. That alone I've seen down in the Khz range. And I've seen it do a crude type of FM modulation within a chip to show up as side bands like a picket fence all up and down the spectrum. Regards, Doug McKean --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Ethernet Radiated Emissions
I read in !emc-pstc that neve...@attbi.com wrote (in 20021010021029.WVI M20316.sccrmhc03.attbi.com@rwcrwbc56) about 'Ethernet Radiated Emissions' on Thu, 10 Oct 2002: You are seing a spectrum of MLT3 signal, which is 100 Mbit coding. Pardon my naivety, but how does '100 Mbit' relate to frequencies of 30 and 60 kHz? Is this 100 Mbit per week? (;-) -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Re: Ethernet Radiated Emissions
You are seing a spectrum of MLT3 signal, which is 100 Mbit coding. Increased broadband emission is caused because some of the differential mode (DM) signal is either converted into common mode (CM) due to imbalance in the differential signalling or because you have some power/ground noise, most likely power/ground bounce caused by the intentional signal over some common- impedance (e.g. bonding gnd wire in a chip). The parts of the story that have something to do with the first case are balance of the output driver (impedance and signal timing and slope), balance of the components/layout on the way of the signal to the Ethernet connetor, including the (im)balance in the pinout (1-2 vs. 3-6) if you are using regular and not integrated connectors (this happens even at the relatively low frequencies that you have problem with). Lack of good balance in the center-tap of the transformer may also significantly increase DM-CM conversion. If you have noisy environment, where a part of the intentional signal is converted into (CM) noise on the power/ground structure, then it can increase the CM driving voltage (relative to the chassis i.e.enclosure) on the pairs. Center taps on both sides of the transfromer may be paths for CM noise to override the CM chokes and get on the UTP. Be careful with how and where you connect the center taps. You may get some idea of what is happening if you can force link, in which you activate the Tx without actually establishing link with the AUX equipment. Your SW guys should be able to help you with that. That will keep the Tx active regardless of what you connect. I can not help you with the details here, but I hope you can use this and think of some experiments you may perform to figure out what is causing the problems. Good luck, Neven Hi Andy, Most of the ports are linking to offsite support equipment or looped back to get link. The response seems consistent regardless of how it is linked. There is also some tuning; broadband humps up a little higher in one spot or another but not a real big factor. I have tried 50 ft and shorter 3 to 10 ft on all ports, and tried ferrites on the offsite portions of the cables. Using STP on the offsite portion of the cable will be an interesting test. Thanks for the input. Rick Linford -Original Message- From: Andy White (EWU) [mailto:andy.wh...@ewu.ericsson.se] Sent: Wednesday, October 09, 2002 3:39 PM To: Rick Linford Subject: RE: Ethernet Radiated Emissions Hi Rick, Is the problem only when you link more than 2 cables together? What is the length of link cabling when adding cables? I susepect that the BB noise is directly associated with the increased cabling and the lengths becoming resonant. If cable lengths are the issue for the BB, the RE problem is not that easy to resolve. Changing to another UTP will not really improve it, a section of STP (on a link or some of the links) would probably help. I would give it a try. Perhaps a cable ferrite may work on a link cable as well to reduce the BB lump amplitude. 100bT uses a 25MHz source so it may be possible to add some filtering at the pcb but this will probably affect the ENET operation/functionality. Hope you find a simple solution. I liked your 'thanks to the marketing dept for the opportunity to learn' comment - classic :) all the best Andy Andy White, Staff EMC Engineer Ericsson Wireless Communications Inc. San Diego, CA 92121 Tel 858 332 6214 / 877 877 7799 ext 26214 Fax 858 332 7311 e-mail andy.wh...@ewu.ericsson.se -Original Message- From: rlinf...@sonicwall.com [ mailto:rlinf...@sonicwall.com] Sent: Wednesday, October 09, 2002 1:55 PM To: emc-p...@majordomo.ieee.org Subject:Ethernet Radiated Emissions Having worked on Ethernet (100 MB UTP) EMC for a few years, I now find myself lacking understanding of Ethernet communications and how this may be affecting radiated emissions. What is seen on the OATs is broadband noise between 50 and 150 MHz. With two cables connected and linked, broadband is not even out of the noise floor. With the third and subsequent cables linked the broadband increases With all cables attached and not linked there is no broadband. Reducing the resolution shows peaks every 60 kHz. Probing on a linked signal shows peaks every 30 kHz with every other peak (60 kHz) being 20 dB higher. Probed several other types of Ethernet equipment, NICs and switches and this seem consistent across all products and manufactures. I feel the filters and layout is quite good, in that, with cables attached but no link there is no emission. In probing on the board it self the 30 kHz signature is present only on the transmit and receive all other signals and voltages appear clean
Ethernet Radiated Emissions
Hi Andy, Most of the ports are linking to offsite support equipment or looped back to get link. The response seems consistent regardless of how it is linked. There is also some tuning; broadband humps up a little higher in one spot or another but not a real big factor. I have tried 50 ft and shorter 3 to 10 ft on all ports, and tried ferrites on the offsite portions of the cables. Using STP on the offsite portion of the cable will be an interesting test. Thanks for the input. Rick Linford -Original Message- From: Andy White (EWU) [mailto:andy.wh...@ewu.ericsson.se] Sent: Wednesday, October 09, 2002 3:39 PM To: Rick Linford Subject: RE: Ethernet Radiated Emissions Hi Rick, Is the problem only when you link more than 2 cables together? What is the length of link cabling when adding cables? I susepect that the BB noise is directly associated with the increased cabling and the lengths becoming resonant. If cable lengths are the issue for the BB, the RE problem is not that easy to resolve. Changing to another UTP will not really improve it, a section of STP (on a link or some of the links) would probably help. I would give it a try. Perhaps a cable ferrite may work on a link cable as well to reduce the BB lump amplitude. 100bT uses a 25MHz source so it may be possible to add some filtering at the pcb but this will probably affect the ENET operation/functionality. Hope you find a simple solution. I liked your 'thanks to the marketing dept for the opportunity to learn' comment - classic :) all the best Andy Andy White, Staff EMC Engineer Ericsson Wireless Communications Inc. San Diego, CA 92121 Tel 858 332 6214 / 877 877 7799 ext 26214 Fax 858 332 7311 e-mail andy.wh...@ewu.ericsson.se -Original Message- From: rlinf...@sonicwall.com [ mailto:rlinf...@sonicwall.com] Sent: Wednesday, October 09, 2002 1:55 PM To: emc-p...@majordomo.ieee.org Subject:Ethernet Radiated Emissions Having worked on Ethernet (100 MB UTP) EMC for a few years, I now find myself lacking understanding of Ethernet communications and how this may be affecting radiated emissions. What is seen on the OATs is broadband noise between 50 and 150 MHz. With two cables connected and linked, broadband is not even out of the noise floor. With the third and subsequent cables linked the broadband increases With all cables attached and not linked there is no broadband. Reducing the resolution shows peaks every 60 kHz. Probing on a linked signal shows peaks every 30 kHz with every other peak (60 kHz) being 20 dB higher. Probed several other types of Ethernet equipment, NICs and switches and this seem consistent across all products and manufactures. I feel the filters and layout is quite good, in that, with cables attached but no link there is no emission. In probing on the board it self the 30 kHz signature is present only on the transmit and receive all other signals and voltages appear clean. Is this the nature of Ethernet 100 MB over Unshielded Twisted Pair? Could this be the fault of the UTP cables? If so any suggestions on the type of UTP cable to purchase? Thanks in advance for your time and responses. Rick Linford And thanks to a marketing department for this opportunity to learn, by believing 6 ports of 100 MB is need in the home. winmail.dat
Re: Ethernet Radiated Emissions
I read in !emc-pstc that rlinf...@sonicwall.com wrote (in D5FCAC81D18F0 d4e8e7df3734de064f2375...@usexch3.us.sonicwall.com) about 'Ethernet Radiated Emissions' on Wed, 9 Oct 2002: With all cables attached and not linked there is no broadband. Reducing the resolution shows peaks every 60 kHz. Probing on a linked signal shows peaks every 30 kHz with every other peak (60 kHz) being 20 dB higher. That seems like stuff from a switch-mode power supply. -- Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk Interested in professional sound reinforcement and distribution? Then go to http://www.isce.org.uk PLEASE do NOT copy news posts to me by E-MAIL! --- 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: majord...@ieee.org with the single line: unsubscribe emc-pstc For help, send mail to the list administrators: Ron Pickard: emc-p...@hypercom.com Dave Heald: davehe...@attbi.com For policy questions, send mail to: Richard Nute: ri...@ieee.org Jim Bacher: j.bac...@ieee.org All emc-pstc postings are archived and searchable on the web at: http://ieeepstc.mindcruiser.com/ Click on browse and then emc-pstc mailing list
Ethernet Radiated Emissions
Having worked on Ethernet (100 MB UTP) EMC for a few years, I now find myself lacking understanding of Ethernet communications and how this may be affecting radiated emissions. What is seen on the OATs is broadband noise between 50 and 150 MHz. With two cables connected and linked, broadband is not even out of the noise floor. With the third and subsequent cables linked the broadband increases With all cables attached and not linked there is no broadband. Reducing the resolution shows peaks every 60 kHz. Probing on a linked signal shows peaks every 30 kHz with every other peak (60 kHz) being 20 dB higher. Probed several other types of Ethernet equipment, NICs and switches and this seem consistent across all products and manufactures. I feel the filters and layout is quite good, in that, with cables attached but no link there is no emission. In probing on the board it self the 30 kHz signature is present only on the transmit and receive all other signals and voltages appear clean. Is this the nature of Ethernet 100 MB over Unshielded Twisted Pair? Could this be the fault of the UTP cables? If so any suggestions on the type of UTP cable to purchase? Thanks in advance for your time and responses. Rick Linford And thanks to a marketing department for this opportunity to learn, by believing 6 ports of 100 MB is need in the home. winmail.dat
