Square Slot Antenna for Wide Circularly Polarized Bandwidth and Axial Ratio Beamwidth

Abstract

Design investigation and experimental results of a coplanar waveguide (CPW) fed square slot antenna that gives wideband circular polarization are proposed in this article. This circular polarization characteristic is achieved by embedding a square shape stub to left bottom corner and a L-shaped strip to the right upper corner of the slot. A high impedance bandwidth of 87.8% (3.6-9.0 GHz), a wide axial ratio bandwidth of 73.05% (4.2-9.0 GHz) and wide 3-dB axial ratio beamwidth of 90° in the entire frequency range of interest is achieved with this antenna structure. To improve the 3-dB axial ratio bandwidth more, three slots (two horizontal and one vertical) are scratched at the exterior periphery of the ground plane. These perturbation assemblies are accountable to excite orthogonal modes and helps to increase in axial ratio bandwidth.  The designed antenna displays the constant and steady radiation patterns in the complete frequency range of concern. The overall dimension of the presented compact antenna is 0.24λ×0.24 λ ×0.01λ.