A method for evaluating radiation efficiency based on a modal approach

Radiation efficiency is an important parameter, especially for electrically small antennas. It can be computed directly from the method-of-moments impedance matrix, and also more generally by employing modal decomposition through characteristic modes. This advantageously enables us to study separately the effect of the radiating shape and the feeding. The proposed method does not require any modification of the Electric Field Integral Equation implementation. A perfectly conducting antenna is considered as the only input to the modal decomposition. The conductive losses are taken into account once the surface currents are calculated. Good agreement is observed for the proposed treatment of the skin effect. Verification of the method is numerically performed on an fractal antenna, a thin-strip Sierpinski curve of various iterations. A full-wave software FEKO with implemented IBC is used for comparison purposes.