# Thevenin and S parameters - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Camelot
Post subject: Thevenin and S parameters... Posted: Fri Jan 26, 2007 11:18 am

Captain

Joined: Fri Jan 19, 2007 10:36 am
Posts: 7
Hello,
I’m have “little” doubt about s-parameter simulations . My question is very simple but I do not know if the answer is the same .
The Thevenin theorem can be applied to a s-parameter simulation?
That is, if I do a simulation using a port P1 with 50 ohm where at valley of the port I’ve connected 2 impedences, one in parallel Z1 and one in series Z2. Supposing I obtained S11 at frequency f1. Then, if I incorporate the impedence Z2 (at frequency f1) in the port 1 impedence (using Thevenin), can I obtain the same S11 parameters for f1 fequency?

Camelot

Top

IR
Post subject: Posted: Fri Jan 26, 2007 3:18 pm

Joined: Mon Jun 27, 2005 2:02 pm
Posts: 373
Location: Germany
Hi Camelot,

In S-parameters you can short voltage sources, but you can't create an open circuit which is required to create the equivalent resistance for Thevenin. You can only connect the network characteristic impedance to derive each of the S-parmaters.

Hence Thevenin theorem applies only at DC and low frequency networks where it is possible to use open-circuit, but not to RF/Microwave networks.

_________________
Best regards,

- IR

Posted  11/12/2012

RF Cafe Software

Wireless System Designer

RF & EE Symbols Word
RF Stencils for Visio
Calculator Workbook
RF Workbench
Smith Chart™ for Visio
Smith Chart™ for Excel

1996 - 2022
Webmaster:
Kirt Blattenberger,
BSEE - KB3UON

RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...

All trademarks, copyrights, patents, and other rights of ownership to images and text used on the RF Cafe website are hereby acknowledged.

My Hobby Website:
AirplanesAndRockets.com

Try Using SEARCH
to Find What You Need.
There are 1,000s of Pages Indexed on RF Cafe !