A Compact and Broadband Circularly Polarized Horn Antenna

In this paper, a compact and broadband circularly polarized horn antenna that is composed of a horn cone, a circularly polarizer (CP) and a compact TE
₁₀
-TE
₁₁
mode converter is proposed. By drilling holes on a dielectric plate with high dielectric constant, a gradient effective permittivity is realized, which can effectively enhance the bandwidth of the CP. Meanwhile, a rectangular-to-circular waveguide transitions with intermediate octagonal-shaped sections is employed to design this antenna. By using these designs as a feed network, a broadband circularly polarized horn antenna with compact size (5.88λ
₀
, where λ
₀
is the wavelength at 5.75 GHz) is achieved. The simulated results show that the 3 dB axial ratio bandwidth is 57.4% (4.1-7.4 GHz) and aperture efficiency is better than 60%.