Thank you, now that I understand that 20 H means the power plane outside edge is set back from the ground plane edge a distance 20 times the separation between the two planes, it is possible to opine on the subject.
Looking at the fringing field set up by potentials and gradients between the two planes, if you follow the 20 H rule the radiation efficiency will be much less, the quasi-static and induction fields will be there, but much less of the energy will break off and radiated as a traveling electromagnetic wave. > From: Cortland Richmond <72146....@compuserve.com> > Date: Sun, 27 Nov 2005 20:47:48 -0500 > To: ieee pstc list <emc-p...@ieee.org> > Subject: Re: Suppression of radiated emissions and spread spectrum clocking > > Ken Javor wrote > >>> I didn't know what the 20 H rule was either, just assumed everyone else > did... << > > See > http://www.qsl.net/wb6tpu/si-list4/0391.html > page 9 of http://www.ansoft.com/thewave/Shielding_and_Decoupling.pdf > http://factaee.elfak.ni.ac.yu/fu2k12/fu04.html > and others (search on "20H rule.") > > RF between two equally sized planes does radiate from the slot formed at > the edge - but RF on a small plane over a larger one also radiates from the > slot around the smaller. We don't want to put patch antennas on a board > while trying to avoid other problems. Thus the controversy. > > > > Cortland > KA5S > > - > ---------------------------------------------------------------- > 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: > > Jim Bacher: j.bac...@ieee.org > David Heald: emc-p...@daveheald.com > > 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: Jim Bacher: j.bac...@ieee.org David Heald: emc-p...@daveheald.com All emc-pstc postings are archived and searchable on the web at: http://www.ieeecommunities.org/emc-pstc
