zhangjerome wrote on Jul 13th, 2008, 4:23am:H, Pancho. As I know, the transducer gain is a function of S21 and other parameters, such as source and load reflection coefficients.
All incomplete knowledges are always useless.
You don't seem understand basic of RF. But this is not restricted to you.
1/S21 is a insertion loss.
Definition of insertion loss is same as inverse of sqrt(transducer gain).
See circuit theory text book, especially on filter design.
http://en.wikipedia.org/wiki/Power_gainIf you think the following, you must consider reference impedance of S-parameters definition. In the following, what values are used as reference impedances(Z01 and Z02) of S11, S12, S21, S22 ?
http://www.maurymw.com/support/faqs/faqs/faq9.html Gamma_S=(ZS-conj(Z01))/(ZS+Z01), ZS is source impedance.
Gamma_L=(ZL-conj(Z02))/(ZL+Z02), ZL is load impedance.
If Z01=conj(ZS), Gamma_S=0.
If Z02=conj(ZL), Gamma_L=0.
Here these are not matching.
So S21=sqrt(Transduder Power Gain) is satisfied.
Usually ZS and ZL are real impedances such as 50ohm.
Again You have to learn measurements using actual instruments. Not "EDA Tool Play".