Re: [SI-LIST] : Re: Differential impedance

Weston Beal (
Thu, 5 Feb 98 16:41 CST

] Nirmal,

] re: Zdiff = 2 * Zodd (of one of two identical lines?)

This equation assumes that only the odd mode is stimulated, which
should be a valid assumption if the differential driver and the
differential trace pair are designed correctly. The true definition
of differential impedance includes both even and odd mode impedance.

] Isn't this only true if there is no coupling between the differential
] signal lines and that a true transmission line assumes that there is
] coupling between conductors (+/-, source/return, etc.)?

] Regards,

] Michael E. Vrbanac
] Cisco Systems, Inc.
] 170 W. Tasman Dr.
] San Jose, CA 95134
] (408)526-4692 (phone)
] (408)526-4184 (fax)

Weston Beal                     Signal Integrity Engineer
"A little bit of knowledge is a dangerous thing"