Dual-Circularly Polarized Antenna With ±65 3 dB Axial Ratio Beamwidth in Entire Upper Hemisphere Space

In this letter, a dual-circularly polarized (DCP) antenna with high port isolation and a wide 3 dB axial ratio (AR) coverage is designed for satellite communication applications. Vector projection analysis reveals that the AR degradation of circularly polarized antennas at low elevation angles is primarily attributed to the insufficient vertical polarization components with appropriate phase characteristics. To address this limitation, a metallic cavity structure is introduced to the antenna element to enhance the vertical polarization radiation component. Precise tuning of placed notches further enables phase optimization of these vertical components, achieving high-purity DCP radiation. Finally, the prototype is processed and measured to determine its effectiveness in covering the 1.55 GHz to 1.6 GHz, where port isolation greater than 20 dB and 130° AR beamwidth in the upper hemisphere is achieved.