IMPROVED PERFORMANCE OF CIRCULARLY POLARIZED ANTENNA USING SEMI-PLANAR CHIRAL METAMATERIAL COVERS

The influence of semi-planar chiral metamaterial (CMM) structures on the important characteristics of circularly polarized (CP) antennas is investigated in this paper. Based on this idea, CP planar two-arm Archimedean spiral (ARSPL) antenna and helical antenna are designed and the effects of chiral covers on their gain (or directivity), axial-ratio (AR), and return loss are considered. The results demonstrate that this method is greatly effective and the addition of a semi-planar CMM cover at an optimized distance over the CP antenna, significantly improves its gain and axial ratio.