Darshan According to my experience=2C 1MHz should be cared=2C which is the freque= ncy not the signal speed=2E However=2C the exact frequency depends on the= stack-up of the PCB=2E In low frequency domain=2C the resistive impedance is large=2E The power = or ground plane should not be used=2E Single-ground should be applied=2E = Otherwise=2C there is resistive coupling=2E If the return path is needed=2C a testing board could be made=2C which is= of two-layer=2E The top is for signal and the bottom is for ground=2E A = maganetic probe is applied to measure the tangent H on the ground plane=2C= where J=3DH=2E We have used this kind of PCB to study the return path of= signal of 2MHz=2E Maybe in the low frequency=2C the H is difficult to be= measured=2E Hope this is helpful=2E Best Regards Zhangkun 2004=2E12=2E2 ----- Original Message ----- From=3A Darshan Mehta =3Cdarshanmehta2k=40yahoo=2Ecom=3E Date=3A Wednesday=2C December 1=2C 2004 11=3A00 pm Subject=3A =5BSI-LIST=5D Power and Ground Plane area =3E Hello Everybody=2C =3E = =3E I was reading one of the IEEE paper on topic =22EMC Analysis=22 by Dr= =2E = =3E Tom Van=2E He says that Return current takes the least impedance = =3E path=2E If the signal speed is 1 KHz=2C there is no need of Power or = =3E Ground Plane because even if you have Power Plane=2C the return = =3E current will not effectively utilize the plane=2E So my question is=2C= = =3E how we should decide at what signal speed we should use Plane area = =3E for Power and Ground=2E Is there is any specific formula for that=2E = =3E Thanks=2E =3E Best Regards =3E = =3E = =3E Darshan Mehta =3E = =3E = =3E = =3E = =3E = =3E --------------------------------- =3E Do you Yahoo!=3F =3E Meet the all-new My Yahoo! =96 Try it today! = =3E = =3E ------------------------------------------------------------------ =3E To unsubscribe from si-list=3A =3E si-list-request=40freelists=2Eorg with =27unsubscribe=27 in the Subje= ct field =3E = =3E or to administer your membership from a web page=2C go to=3A =3E http=3A//www=2Efreelists=2Eorg/webpage/si-list =3E = =3E For help=3A =3E si-list-request=40freelists=2Eorg with =27help=27 in the Subject fiel= d =3E = =3E List FAQ wiki page is located at=3A =3E http=3A//si-list=2Eorg/wiki/wiki=2Epl=3FSi-List=5FFAQ =3E = =3E List technical documents are available at=3A =3E http=3A//www=2Esi-list=2Eorg =3E = =3E List archives are viewable at=3A = =3E http=3A//www=2Efreelists=2Eorg/archives/si-list =3E or at our remote archives=3A =3E http=3A//groups=2Eyahoo=2Ecom/group/si-list/messages =3E Old (prior to June 6=2C 2001) list archives are viewable at=3A =3E http=3A//www=2Eqsl=2Enet/wb6tpu =3E = =3E = =3E ------------------------------------------------------------------ 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