Excitation of a two-arm metaspiral antenna

The radiation characteristics of a two-arm metamaterial-based spiral antenna (metaspiral) are investigated as a function of excitation amplitude coefficient m, where a situation of m = 1 means that the spiral is excited in balanced mode. It is found that the radiation field in the antenna axis direction (z-direction) decreases as m is decreased. The gain in the z-direction drops by 1-dB at m = 0.6. The symmetry of the radiation pattern obtained at m = 1 is almost retained at m = 0.6.