Gurus, I can explain ringings on a TDR data but can anyone tell me why I am seeing this on a Return Loss data for a layout that is geometrically correctly done? This is a simulation result based on a .brd file in allegro and I was wondering if I was doing something wrong here as far as modeling the device or the SMAs. This board uses Fr-4 and the traces are around 4.5 inches long diff pairs. I know the impedances are kept constant (same geometry) throughout the whole path and return path is ideal. Rgds, Qazi -- PRIVACY WARNING: For auditing purposes, a copy of this message has been saved in a permanent database. ------------------------------------------------------------------ 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 technical documents are available at: http://www.si-list.net 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