Re: Why best results of s21 and s11 don't occures in same frequency?
Hi,
I notice that there are two definitions of insertion loss going around. The first is simply S21, while the less used one is |S21|^2 /(1-|S11|^2). Personally I always differentiate between S21 and insertion loss. Which one are you referring to?
Anyway, one point is that not all of the power is reflected or transmitted, some of it is dissipated in the circuit. This breaks the relationship between S21 and S11. If you look into absorptive filters, for example, you will see that there's hardly any relationship between S11 and S21.
regards,
Aaron