antenna-theory.com

[eechen]

Recently learned that f(Gmax) is (usually) not always same as f(S11).

One example: ½ ? dipole where at Gmax, Z=72+j ~200, so S11 not lowest.

Any othere examples?

[admin]

It is definitely not true that the best impedance match has the highest gain across frequency. You can have distinct points across frequency for highest efficiency, highest gain, and best return loss.

[eechen]

Can anyone show some math? Something pointing to f1(Gmax) = f2(S11min)? Where f1 != f2, but it hightlights how they are tied together?

How about this:

G=4pi*A,e/lambda^2, where Lambda=c/f1

Zin = Zo{[Z,A+ jZo*tan(2pi*f2/c*L)] / [Zo+jZ,A*tan(2pi*f2/c*L)]}

Where

f1=f2 then both G and Zin (and S11) occur at same frequency.

f1 != f2 helps explain why f(G,max) != f(S11)