Compact Dual-Circularly Polarized Reflectarray Antenna Using Semicircle Strips Elements With Independent Focus and Beam Directions

This article introduces a compact dual circularly polarized (DCP) reflectarray antenna (RA) with independent focus and beam directions for satellite communication. The reflectarray employs semicircle strip elements with slots on their diameters, which facilitates adjusting the opening direction and slot width, providing hybrid phase shift, and controlling the focus and beam directions of the reflectarray independently. The mechanism for the hybrid phase is analyzed using the linear polarization scattering matrix. The achieved reflectarray can provide independent left-hand circularly polarized (LCP) and right-hand circularly polarized (RCP) beams in the ±20° range. The profile of the single-layer reflect plane is 0.136 \lambda _{0} , and the focal length to diameter ratio (F/D) of the compact reflectarray is 0.5. The reflectarray prototype is designed, fabricated, and measured. The experimental results show that the peak gain of the reflectarray is 21.3 dBic at −20° under RCP excitation and 20.1 dBic at 20° under LCP excitation, respectively. The measured 1-dB gain and 2-dB axial ratio (AR) bandwidth are 10.6% (9.75-10.8 GHz) and 5.9% (9.75-10.35 GHz) with LCP helix and RCP helix antenna excitation, respectively. The proposed compact DCP RA could be an alternative for satellite communication.