An electrically large circularly polarized metallic cavity antenna with wide beamwidth for satellite applications

A circularly polarized metallic cylindrical cavity antenna with wide beamwidth is proposed in this paper. The idea is to enlarge the antenna size for high-frequency applications such as C-band, X-band, K-band and other higher-band systems but still maintain good performance. A C-band prototype is designed, fabricated and measured. The overall dimensions are 1.35λ
₀
× 1.35λ
₀
× 0.83λ
₀
, which is electrically large compared to the central operating wavelength λ
₀
. The proposed cavity antenna is excited by the insertion of a coaxial probe, and circular polarization is realized by an inserted screw. The unidirectional radiation of the cavity antenna is achieved by making one port of the cylindrical resonant cavity open while keeping the opposite one closed. An upper ring is added to the cavity antenna near the open port to widen the radiation pattern. The measured -10 dB impedance bandwidth and 3 dB axial ratio bandwidth is 1.36 GHz (6.02 GHz to 7.38GHz) and 340 MHz (6.59 GHz to 6.93 GHz) respectively. The measured and simulated half-power beamwidths are 137° and 135° in two principal planes respectively, which shows good agreement.