Design of New Single-Layer Multiple-Resonance Broadband Circularly Polarized Reflectarrays

Based on the idea of a single-layer multiple-resonance structure for a linearly polarized reflectarray, two broadband circularly polarized reflectarray elements are presented in this letter. One is a double-ring-shaped element, and the other is an I-ring shaped element. The principle of broadband circular polarization is studied by analyzing the surface current distribution of the elements. Then, by using an angular rotation technique, reflectarrays with these two elements are designed and measured. The reflectarrays ( $6.5\lambda \times 6.5\lambda$ at the center frequency of 10 GHz) demonstrate excellent performance of more than 30% antenna bandwidth [the overlapping 3-dB axial-ratio (AR) and 1-dB gain bandwidths]. The aperture efficiency can go up to 58.55% and 59.94%, respectively.