From: Farrokh Mottahedin (firstname.lastname@example.org)
Date: Wed Jan 24 2001 - 11:44:04 PST
There seems to be a phenomenon that on a differential transmission line, an
increase in the characteristic impedance (Zo) will help to reduce IR losses
due to skin effect.
Now, we know that Zo = sqrt(L/C). Likewise the IR losses due to skin
effect can be summarized generally as 4.34 (R/Zo+GZo) in dB/meter. R and G
are the load resistance and admittance.
Conceptually, it also makes sense that if a transmitter sees a larger Zo
(the transmitter does not see the load directly, but only sees the line
ahead), less current will flow, and since the load doesn't change, there
will be less power loss. But if the drivers are current sources, then the
current should be constant, and a larger Zo serves only to cause more IR
loss. Here I am looking for some math to clear all this up rather than to
rely on intuition.
Cisco Systems, Inc.
Gigabit Systems Business Unit
170 W Tasman Drive
San Jose, Ca 95134-1706
Phone: (408) 525-9185
Fax: (408) 527-8254
**** To unsubscribe from si-list or si-list-digest: send e-mail to
email@example.com. In the BODY of message put: UNSUBSCRIBE
si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP.
si-list archives are accessible at http://www.qsl.net/wb6tpu
This archive was generated by hypermail 2b29 : Tue May 08 2001 - 14:30:43 PDT