>An accurate way to model a 50 Ohm microstrip transmission line is with a pair of transmission lines in >parallel: one T-line for the lower reference plane and another T-line for the upper reference plane. If >the 50 Ohm line happens to be exactly in the center of the two reference planes, is represented by a two >100 Ohm T-lines in parallel. It seems to me that you are referring to a stripline (not a microstrip). Since a microstrip is an outer layer trace, it can have only one reference plane. Best Regards, Abe ------------------------------------------------------------------ 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