Transmission impedance from two port S-parameter for a Diode

Hi everyone,

I have a question regarding scattering parameters. How can I extract the impedance of a two port device (Diode) out of a two port S-parameter measurement?

When using one port S-parameter measurement, Z is calculated by transforming the S11 to Z for a specific working point and frequency. Is it correct to transfer the S12 or S21 (which are (almost) identical by a Diode) to Z to get the impedance of the device?

Thank you.

Best regards.

Is it an ordinary diode or special purpose one ?

If you have a working diode, s21 and s12 should be quite different! One correct way would be to transform your s-parameters to y-parameters and use the pi-model. The shunt elements of the model are y11+y12 and y12+y22 and the series admittance is -y12 or -y21. This would be the transfer addmittance you are looking for, i think.

It is an ordinary diode but for higher frequencies

Why should S21 and S12 be quite different, diode is a 2 port device!
I wasn?t that sure if -y12 or -y21 of the pi-model is enough :). Wouldn?t it be better to use the average of y12 and y21, what do think?

@ BigBoss and Kohnjoe: Thank you for your time :)

You're welcome.

Ah sorry, my mistake!

They should be also equal.

Ops yes sure ;)... Thank you for the help. I think now I’m more sure that I’m on the right way