Low cross-polarization wideband circularly polarized reflectarray antenna

Abstract

In this paper, a low cross-polarization wideband circularly polarized (CP) reflectarray antenna is proposed. The design features a 20 × 20 element array fabricated on an FR-4 substrate with 0.5λ0 element spacing, resulting in a 50 cm × 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 is optimized to minimize cross-polarization and achieve the desired phase response. The unit cell geometry is analyzed using an equivalent circuit model for comprehensive understanding. A 400-element prototype is fabricated and fed by a custom-designed septum horn antenna. Measured results show excellent agreement with 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. © 2025 Elsevier GmbH