BROADBAND MONOPOLE ANTENNA WITH WIDE- BAND CIRCULAR POLARIZATION

Abstract—A novel broadband monopole antenna design with wideband circular polarization (CP) characteristic is presented. This antenna consists of a feed line and a step-shaped ground plane which is formed by cutting a notch in the upper left corner of an asymmetric ground plane. The asymmetric ground plane is capable of exciting two orthogonal electric field vectors with equal amplitude and 90 ◦ phase difference (PD) for CP. By cutting a notch, the 10-dB impedance-bandwidth can be enhanced greatly and the 3-dB axial ratio (AR) bandwidth is also improved meanwhile. The measured impedance-bandwidth is about 5.96GHz (84.7%) from 4.06 to 10.02GHz, and the measured AR-bandwidth is about 2.64GHz (36.5%) from 5.91 to 8.55GHz. The results show that the antenna can achieve wide impedance-bandwidth and wide AR-bandwidth simultaneously. 1