Low cross-polarization wideband circularly polarized reflectarray antenna

In this paper, a low cross-polarization wideband circularly polarized (CP) reflectarray antenna is proposed. design features a 20 x 20 element array fabricated on an FR-4 substrate with 0.5 lambda 0 element spacing, resulting a 50 cm x 50 cm aperture. The unit cell incorporates loaded circular rings with a T-stub configuration, where parallel strips are embedded within the gap. Through design evolution and parametric analysis, the structure optimized to minimize cross-polarization and achieve the desired phase response. The unit cell geometry analyzed using an equivalent circuit model for comprehensive understanding. A 400-element prototype fabricated and fed by a custom-designed septum horn antenna. Measured results show excellent agreement simulations, with the reflectarray achieving a peak gain of 28.3 dBic at 6 GHz and a cross-polarization level below -22 dB, crucial for reducing interference. The antenna demonstrates 54 % aperture efficiency at 6 GHz, with a 67.1 % 3 dB axial ratio (AR) bandwidth (4.08-8.20 GHz) and a 51.7 % 3 dB gain bandwidth (4.85-8.24 GHz). These results validate the proposed design for wideband CP reflectarray antennas, particularly for C-band applications.