Hi all, I am currently designing a PCB backplane for differential signals at 2.5 Gbit/s. I use a differential receiver with 100 Ohm termination. For coupled transmission lines, which impedance should match 50 Ohm, the even-mode impedance or the even-mode impedance ? After reading some documentation on the topic, I am confused. On one hand, I read that differential signals propagate in odd-mode since coupled transmission lines are driven with equel magnitude and 180° out of phase ("High-speed Digital System Design", S.H. Hall, G.W. Hall, J.A. McCall, p.53) . On the other hand, I read that since differential signals are launched from silicon devices, the gates that driver these signals are both referenced to ground, resulting in even-mode coupling (http://www.amp.com/simulation/files/papers/98060A 5.pdf p.19). Can anyone help me to clarify this point. Thanks in advance. Alexis -- Alexis Lestra Tachys Technologies Les Algorithmes, Batiment Aristote A 2000, route des Lucioles F-06901 Sophia-Antipolis Cedex e-mail : alestra@xxxxxxxxxx ------------------------------------------------------------------ To unsubscribe from si-list: si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field For help: si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field List archives are viewable at: //www.freelists.org/archives/si-list Old list archives are viewable at: http://www.qsl.net/wb6tpu