A Low-Profile Circularly Polarized Directional Antenna with Wide Beamwidth and Wide Bandwidth

This paper presents a low-profile broadband wide-beam directional circularly polarized (CP) antenna based on crossed dipoles. The design consists of two sets of crossed dipoles, each connected to the inner and outer conductors of a coaxial line. Each dipole set features two bowtie-shaped patches linked by a vacant-quarter ring, whose circumference equals a quarter of the center wavelength. This ring introduces a 90-degree phase shift, enabling circularly polarized radiation. To enhance performance, four parasitic elements are strategically placed at the corners. The parasitic patches contribute to bandwidth expansion, while the vertical parasitic plates improve beamwidth coverage. Simulation results demonstrate that the antenna achieves good |S11| and axial ratio performance within the 1.2-2.1 GHz range. Additionally, the half-power beamwidth (HPBW) is significantly improved compared to designs without vertical parasitic plates, highlighting its strong potential for future wireless communication applications.