camelot wrote:
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 of 50 ohm where at valley
of the generator I've connected 2 impedences, one in parallel Z1 and
one in series Z2. Supposing I obtained S11 at frequency f1. Then 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?

From: "Fields and Waves ...", by Ramo and Whinnery:
"It must be emphasized, as in any Thevenin equivalent
circuit, that the equivalent circuit was derived to
to tell what happens in the *load* under different
*load* conditions, and significance cannot be automatically
attached to a calculation of power loss in the internal
impedance of the equivalent circuit."

Power loss in the internal impedance of the Thevenin
equivalent circuit is related to the s-parameters.
|s11|^2 is power reflected from the network input
divided by the power incident on the network input.
--
73, Cecil http://www.w5dxp.com