matching an antenna = low return loss = good radiation?

for example, i have made 2 monopole, similar shape but different size antennas

their impedance is orginally different, at 2.4GHz

antenna A is born with a 50Ohm input impedance(resonant at 2.4GHz)
antenna B is born with only a 25Ohm input impedance at 2.4Ghz( resonant at other freq, say at 4GHz, Z = 50Ohm)

given a 50Ohm transmittion line at 2.4GHz
antenna A could attain a maxiumum power transfer without any matching circuit
while antenna B is matched with circuit to 50Ohm

So at last, same type monopole , with similar shape, different size, but they are matched to 50Ohm at same frequency 2.4GHz

So do they radiate in same manner at 2.4GHz?
eg. radiation efficiency, pattern, and other antenna behaviour

THx all!

geppei,

Yep, as they are both monopoles with similar shapes, both will have the same radiation properties. In theory the only real difference will be in terms of impedance bandwidth. In practice, you will also get some extra losses in the matching network of antenna B. For this particular case of 50 Ohm vs 25 Ohm, I guess the difference will not be particularly large.

Regards,
Peter

Hi,

I say yes if antenna B is resonant at both frequencies.
If it is not it will dissipate the applied power as heat.

on1aag.

You will get two matched monopoles but different gain and pattern because these parameters depends on the size of the monopole.
because you are loking at the same freq. in different sizes. if you will scale the freq. with size you will get the same gain and pattern.