how to find i/p & o/p impedance from S - parameter of transistor?

hello to all
I have S - parameter of transistor for band of frequency and I want to use transistor at one frequency but I don't know how to use s - parameter to find input and output impedance of transistor so I can design matching network to match 50 ohm resistor.

Thank You

In the data display plot the smith chart and get the input impedance from S(1,1) and output impedance from S(2,2)..

---------- Post added at 06:52 ---------- Previous post was at 06:51 ----------

By the way which software are u using?

I am Using the software "smith"
But i want to know how to plot s11 and s22 on smith chart ?

Gamma_in=S(1,1)+S(1,2)*S(2,1)*Gamma_L/(1-S(2,2)*Gamma_L)
Gamma_L=(ZL-Z02)/(ZL+conj(Z02))
Gamma_in=(Zin-conj(Z01))/(Zin+Z01)
From these, evaluate Zin.

Gamma_out=S(2,2)+S(2,1)*S(1,2)*Gamma_S/(1-S(1,1)*Gamma_S)
Gamma_S=(ZS-Z01)/(ZS+conj(Z01))
Gamma_out=(Zout-conj(Z02))/(Zout+Z02)
From these, evaluate Zout.

The Designer's Guide Community Forum - How to plot "input reflection coefficient" in ADS
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What do you mean by "smith" ?
Describe in detail and correctly.

Thank you very much for answer...
your answer is very useful for me and almost solved my problem.
I am using "qsmith" software ...

I have one more problem.....
If SOURCE of first FET and DRAIN of second FET is connected then, How to use S - parameter ? Using same type of FET .
Means How to use combination of S11 and S22 .

Thank You.

Hello Sir,

I am using quad ring of 4 FETs . source of 1st connecyed to drain of 2nd , source of 2nd connected to drain of 3rd like this ......source of 4th connected to drain of 1st.
Signal applied between two opposite point of quad ring , How to use S - parameter for circuit to design matching circuit ?
Circuit is:-

Thank You.

(1) What is your native language ?

(2) How do you get S-parameters of FET ?
Actually measurement by yourself ?
Touchstone Data provided by FET supplier ?

(3) Do you understand that S-parameters of FET are dependent on DC bias points such as Vgs, Vds and Idrain ?
Do you understand DC operation point of FETs in your target circuit ?

(4) Do you understand that input impedance characteristics seen from each port are highly dependent on drive power such as RF power and LO power.
So static S-parameters are not so useful for your application.

(5) Do you understand Touchstone Data provided by FET supplier is S-parameter for common source configuration ?
So you can't apply it for your appllication even if DC operation points for S-parameter are proper for your application.

If you don't mind using static S-parameters although target circuit is highly nonlinear so static S-parameters are of no use,
measure S-parameters of FET as three port device(drain, gate, source) under proper DC bias operation points.

However you should use nonlinear model parameters of FET.
Do not use small signal S-parameters under specific DC bias points.
The Designer's Guide Community Forum - Model for HJFET NE3514S02 transistor!

Hello Sir,

1. My netive language is Hindi(Indian), but always use English(UK).

2.I get S - parameter from data sheet of FET.

3. Yes I understand S - parameter depend on DC biasing of FET. I am not providing any DC biasing to my circuit , I want drive my circuit on LO drive.

4. I don't understand input impedance characteristics of each port.

5. I don't understand Touchstone Data.

I have only S - parameter at different DC biasing of FET.
So , it is not possible to match such circuit.
Or , any other procedure/analysis of matching this circuit ?

Thank You

Are S-parameters available for your purpose in Data Sheet ?
that is, are there S-parameters under no bias feeding condition in Data Sheet ?

See the followings.
https://www.edaboard.com/thread181949.html
https://www.edaboard.com/thread169169.html

"Touchstone Data" is an industrial standard format for S-parameter.
In RF world, there is no one who don't know "Touchstone Data".
Read very beginner's book on RF engineering.

Before considering bias point of S-parameter, you have to understand 2-port S-parameters of FET.
You can't apply 2-port S-parameters of FET to your circuits.

Again, if you don't mind using static S-parameters although target circuit is highly nonlinear so static S-parameters are of no use,
measure S-parameters of FET as three port device(drain, gate, source) under proper DC bias operation points.

Again are 3-port S-parameters available in Data Sheet ?

Surely read my appends.
You can not apply 2-port S-parameters of FET which are measured under common source configuration, for example.
Again, you should use nonlinear model parameters of FET.
Do not use small signal S-parameters under specific DC bias points.
The Designer's Guide Community Forum - Model for HJFET NE3514S02 transistor!