An Electrically Large Metallic Cavity Antenna With Circular Polarization for Satellite Applications

An electrically large metallic cavity antenna with circular polarization (CP) is proposed in this letter. The aim is to increase the size of satellite antennas working in the Ku-band and other higher-frequency bands through low cost and easy fabrication. A brass C-band antenna prototype is designed, fabricated, and measured for concept verification. The overall dimensions of the antenna are 0.67λ₀ × 0.67λ₀ × 0.83λ₀ at the working frequency. The resonant mode of the proposed cavity antenna is excited by a coaxial feeding probe, and circular polarization is realized by an inserted perturbation screw. The measured impedance bandwidth for | <i>S</i>₁₁| ≤ -10 dB and 3-dB axial-ratio bandwidth are 1.02 GHz (6.07-7.09 GHz) and 320 MHz (6.59-6.91 GHz), respectively. The measured gain is 8.5 dBic across the whole 3-dB axial-ratio bandwidth. The measured 3-dB axial-ratio beamwidths at the central frequency are 150^° and 148^° in the <i>xoz</i>- and the <i>yoz</i>-planes, respectively, which is wide enough to cover the >; 0-dBi gain beamwidths of 120^° for practical engineering applications. The measured and the simulated results show good agreement.