Dual-Frequency Dual-Circularly-Polarized Printed Slot Antenna

A slot antenna which realizes dual frequency dual-sense circular polarization is proposed. A printed spiral slot is fed using a T-shaped microstrip feedline. The results show that axial-ratio bandwidths of 4.5% and 3.5 % are obtained for right-hand circular polarization and left-hand circular polarization, respectively. A detailed parametric study and description of circular polarization mechanism are presented.