Performance enhancement of circular polarization reconfigurable monopole antenna using metasurface

A circular polarization-reconfigurable (CPR) monopole antenna for Global Navigation Satellite System (GNSS) applications is proposed. The CPR antenna consists of two meandered monopoles denoted as MP1 and MP2, a switchable feeding network, and a metasurface (MS) using dual-cap mushroom-like unit cells. The two monopoles have tapered shapes for better matching and wider impedance bandwidth. The switchable feeding network is composed of a double-pole double-throw (DPDT) switch and a 90°-phase shifter implemented using a λ
g
/4-microstrip line. The DC control voltages to the DPDT switch determine if the two signals fed to MP1 and MP2 have a phase difference of 90° or −90°, hence generating a RHCP or LHCP signal, respectively. The MS consists of eight dual-cap mushroom-like unit cells and is placed at a distance of h
r
=0.09 λ
0
from the source antenna. Simulation results show that, the MS can increase the boresight gain and the operating bandwidth from 0.4 to 6.6 dBi, and 1.46–1.79 GHz to 1.42–1.88 GHz, respectively.