Quick Question About Power Gains

[EEPC]

Hey guys,

I am designing an LNA and have a quick question regarding the different power gain definitions, e.g. available power gain (Ga), transducer power gain (Gt), etc. From my understanding Ga assumes conjugate (optimal) match at the output and depends only on the input match network, whereas Gt depends on matching at both input and output. I am designing for gain using the available gain circles (Ga_circles) in ADS, so I put a conjugate match at the output and designed the input based on where I want to fall on the various circles (gain, NF, etc).

My question is: when I'm simulating the entire amplifier network in ADS, and also when I fabricate and test the LNA on a network analyzer, is the value of S21(dB) that I simulate/measure equal to the TRANSDUCER power gain? This makes sense to me because when I'm testing or simulating it S21 should take into account the networks at both input and output, right? But in my case, the S21(dB) that I'm measuring is also ideally equal to the available power gain since my output matching network provides a conjugate match?

I hope the question made sense, I guess basically what I'm asking is what kind of power gain am I actually measuring or simulating when I look at S21? Thanks for the help!

 

[D.A.(Tony)Stewart]

Yes S21 is the gain out port 2 from port 1.
and the return loss S12 is the reverse direction is a measure of impedance mismatch and reflected power.

 

[EEPC]

Thanks SunnySkyguy, it would be correct to call |S21|^2 the transducer power gain right? Which is equal to available power gain in this case since my output is ideally a conjugate match?