On the Radiation Resistance of Folded Antennas

The antenna literature appears divided regarding the input impedance of a folded antenna. Is the increase in feed-point impedance for a folded antenna simply an impedance transformation of the single element radiation resistance with no change in radiation resistance or does the folding process actually lead to an increase in the radiation resistance? This paper shows through theory and numerical simulations that the radiation resistance of a folded antenna is effectively – but not exactly – the same as that of a single element. This work serves as a point of clarification regarding the theory of folded antennas.