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https://designers-guide.org/forum/YaBB.pl Design >> RF Design >> voltage gain and S21 relationship https://designers-guide.org/forum/YaBB.pl?num=1150372876 Message started by cybq on Jun 15th, 2006, 5:01am |
Title: voltage gain and S21 relationship Post by cybq on Jun 15th, 2006, 5:01am Hi all, How to caculate the volatge gain of a two port network, knowing S21, S11, S22? I made a simple passive network in ADS and run the S paraamters and transient simualtion, and found S21 is less more than the voltage gain caculated using transient voltage when S11/S22 are not matched. What is those relationship between them? Any answer are welcome. cybq |
Title: Re: voltage gain and S21 relationship Post by milkdragon on Jun 15th, 2006, 9:39am Voltage gain (let's call it Vg) = 20log(Vout/Vin) dB Power Gain (S21,let's call it Pg) = 10log(Pout/Pin) = 10log[(Vout^2/Rout)/(Vin^2/Rin)]=10log[{(Vout/Vin)^2} * (Rin/Rout)]=20log(Vout/Vin)+10log(Rin/Rout) dB So you will see that if the input and output impedance are the same, Pg is essentially equal to Vg. However, if Rin <> Rout, you will see the difference between voltage gain and power gain |
Title: Re: voltage gain and S21 relationship Post by cheelee on Jun 15th, 2006, 6:39pm Have a look at this paper: George D. Vendelin, Jose Carlos Pedro and Pedro Miguel Cabral, "Amplifier and Transistor Gain Revisited", Microwave Journal, Apr 2005 It has the equations relating 2-port S-parameters to voltage, current and power gain. Hope it helps. |
Title: Re: voltage gain and S21 relationship Post by cybq on Jun 15th, 2006, 9:13pm Thanks cheelee. I want to say that S parameter is defined with voltage, for example, S21=b2/a1|a2=0, instead of power gain. I'll search the paper you recommended. cybq |
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