Joe, Assuming rectangular outlines of the planes, you will end up getting a double infinite series of modal resonances from the structure. Depending on where you are on the rectangular planes, some resonances may coincide in frequency and they may add up or may cancel. The more symmetry you have in the structure, chances are getting higher that resonances will line up. Since this depends also on the location on the planes, unless you know that you DO NOT use the planes other than at a selected location, counting on the cancellation becomes tricky. Cancellation that may work at your selected location will not necessarily work at other locations. Also keep in mind that the components on the boards will have a tendency to shift the resonance frequencies around, making it harder in practice to achieve cancellation. Regards, Istvan Joe Paul wrote: >I have a query on resonance of reference planes, (referring to >http://www.sigcon.com/Pubs/edn/ppresonance.htm) > >I under stand that resonance freq corresponds to the time, a disturbance in >reference plane ,take >to return to its origin after reflecting from edges of the board. I have also >read in a different >article that , symmetric board shapes like Square should be avoided as far as >possible for reducing >problems with resonance of reference planes . > >My doubt is > >Is the shape concern due to chance of noise originating at center of board >after reflecting from >all four sides , reaching the center at same phase and adding up ? or is >there any other reason ? >or is the shape concern a myth ? > >Regards >Joe > > ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field or to administer your membership from a web page, go to: //www.freelists.org/webpage/si-list For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List FAQ wiki page is located at: http://si-list.org/wiki/wiki.pl?Si-List_FAQ List technical documents are available at: http://www.si-list.org List archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu