Design of a Coplanar Waveguide-Fed Wideband Compact-Size Circularly Polarized Antenna and polarization-sense alteration

This paper presents the design and validation of a geometrically simple circularly polarized(CP) structure featuring flat gain in the sub-6 GHz 5th generation spectrum. The proposed structure is based on coplanar-waveguide-fed, modified wide slot etched in the ground plane. For generating CP waves, the coplanar ground planes are designed with slight asymmetry in both the horizontal and vertical directions. Furthermore, the ground plane at the back is modified to create an additional current component. The antenna is realized with a compact footprint of 0.36λo × 0.28λo (or 0.1\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\varvec{\lambda }}_{\varvec{o}}^{2}$$\end{document}). The operating frequency is from 2.5 to 6 GHz, which covers all the bands in the sub-6 GHz spectrum of the 5th generation technology. The impedance bandwidth of the antenna is in the range of 2.45 to 8 GHz and the axial ratio (AR) bandwidth is from 2.5 to 6 GHz, corresponding to more than 82% of relative bandwidth. The peak realized gain is 4 dBic, which is relatively high for a bidirectional wideband structure, and very stable throughout the entire operating band with a variation of ± 0.35 dBic. Unlike the design available in the literature (with asymmetrical ground planes), the proposed antenna has a consistent radiation pattern with a minor beam tilt. The design is fully optimized before prototyping and experimental validation. From the application viewpoint, the proposed antenna has the potential to be used in integrated systems. Moreover, a simple method for altering the sense of CP from right-hand CP (RHCP) to left-hand CP (LHCP) and vice versa is studied. This technique is useful for implementation of polarization diversity in the multiple-input-multiple-output (MIMO) environment.