Compact broadband circularly polarized monopole antenna

This paper presents the design of a broadband circularly polarized (CP) monopole antenna. The proposed CP antenna is developed from a primitive structure consisting of only a half-circular patch and an inverted-L feeding strip connected to a coplanar waveguide. By loading a rectangular tuning stub to and etching a sector-ring slot from the half-circular patch and by adding an extended section to the inverted-L feeding strip, one can obtain a measured 3-dB axial-ratio bandwidth of 39.7% for the proposed CP antenna. The designed antenna is relatively compact as compared with another CP monopole antenna of similar structure.