Enhancing Bandwidth of CP Microstrip Antenna by Using Parasitic Patches in Annular Sector Shapes to Control Electric Field Components

This letter finds that bandwidth of a circularly polarized (CP) microstrip antenna can be enhanced by using two annular-sector-shaped parasitic patches. This is because the induced current on the parasitic patches involves both x- and y-components, hence it can control the theta and phi components of the electric field. For the purpose of demonstration, a bandwidth-enhanced CP microstrip antenna is proposed and analyzed. Except from low profile and compact size, its impedance matching can be adjusted while keeping the CP feature unchanged, which simplifies the design process. The axial-ratio bandwidth of the proposed antenna can be effectively increased from 1.3% to 3.3%, while its impedance bandwidth is increased from 4.3% to 6.0%.