Cavity-Backed Broadband Circularly Polarized Cross-Dipole Antenna

This letter presents a broadband circularly polarized (CP) cross-dipole antenna. It consists of crossed dipoles, parasitic elements, a cavity-backed reflector, and a circular ring reflector. The arms of crossed dipoles are divided into two sectors by a slit. The parasitic elements are utilized to significantly enhance the CP bandwidth. A circular ring reflector is adopted to optimize the radiation pattern and improve the gain in high frequency band. The fabricated prototype of the proposed antenna with an overall size of 0.60λ₀ × 0.60λ₀ × 0.21λ₀ (λ₀ is the free-space wavelength at the lowest CP operating frequency) yields a measured impedance bandwidth of 98.2% for |S₁₁|<-10 dB (1.73-5.07 GHz) and a 3 dB axial-ratio bandwidth of 85.5% (1.94-4.84 GHz). The antenna has stable radiation patterns from 1.94 to 4.5 GHz and exhibits a right-hand circular polarization with a peak gain of approximately 10.0 dBic at 3.6 GHz.