For single frequency one can calculate Γin as per the equation above.
So you need to have ΓL and S-para data.
ΓL for 50 ohm char impedance will be (ZL-50)/(ZL+50).
where ZL is load impedance.
ΓL=S22+( S12*S21*Γin)/(1-S11*Γin) equation is valid when there is DUT with bi-directional behavior like amplifier etc.
In this case ΓL is depend on Γin and vice varsa.
For a LOSSLESS network, you can say the (POWER into the network) = (POWER reflected off the network) + (POWER transmitted thru the network)
The old "conservation of power" rule.
Γ is a VOLTAGE reflection coefficient. If you are concerned about POWER, you would be more interested in VOLTAGE²/impedance=POWER. SO POWER is proportional to Γ².
If you normalize the input POWER to equal "1", you can then say that:
Input reflection coefficient is S11,
Output reflection coefficient ( that is ration of power reflected from load to power transmitted towards load)
Transmission coefficient is S12 or you can say isolation
& S21 is gain.
Read book by Gonzalez
Microwave transistor amplifiers.
It does not make any sense if we simply tell the formular from books. You'd better read them yourself. There are many books you can refer to, such as "Microwave Eningeering" and "RF Circuit Design".
can any one tell me what are s parameters of amplifier n what there values tell about for eg if S11 is input impedance and for rf amplifier it should be less that -10db so why is that so? if u have some links or tutorials so plz refer.