CPW-Fed Wideband Circularly Polarized Printed Monopole Antenna With Open Loop and Asymmetric Ground Plane

A wideband circularly polarized (CP) printed monopole antenna with coplanar waveguide feeding is proposed. The antenna is composed of a rectangular monopole, an asymmetric ground plane, and a square-ring with an open gap at the bottom. By utilizing the asymmetric ground plane, CP radiation could be achieved at the upper band first. Then, a rectangular open loop is introduced to obtain wide-impedance bandwidth and broadband CP characteristic. The measured results demonstrate that the 10-dB impedance bandwidth reaches 96.5% (2.76 GHz, 1.48-4.24 GHz) and the 3-dB axial-ratio bandwidth is 63.3% (1.9 GHz, 2.05-3.95 GHz). In addition, parameter studies are performed, and surface current analysis is also given to show the operating mechanism of CP operation.