A broadband circularly polarized monopole antenna employing parasitic loops and defective ground plane

Abstract

A simple printed monopole antenna using parasitic loops and defective ground plane is presented for broadband circular polarized (CP) radiation. For this purpose, two square open loops, which install air gaps at the corner and close to the monopole, are printed on both sides for achieving broadband CP radiation with three minimum axial ratio (AR) points. By using a defective ground plane with a vertical slot and a horizontal slot, additional AR points can be excited to further broaden the AR bandwidth. This design was fabricated, and the measured results show that the antenna with a simple structure achieves both wide impedance bandwidth of 87.2% (2.62-6.67 GHz) and AR bandwidth of 83.9% (2.6-6.36 GHz).