Dual-Frequency Reflectarray Based on Split-Ring Slots

This letter presents a dual-frequency reflectarray (RA). This RA is capable of forming two differently oriented main lobes with the same sense of circular polarization in the directions determined by the reflection elevation angles θ
₀₁
and θ
₀₂
at two closely spaced frequencies. The RA element contains a pair of concentric split-ring slots with different angular rotations. The geometry of the element was modified and optimized to suppress a mutual coupling between the concentric rings. To validate the operation principle, 317-element offset RAs RA_0_20, RA_20_0, RA_30_40, and RA_40_30 were designed to operate at 34.5 and 38.5 GHz for the pairs of elevation angles (θ
₀₁
, θ
₀₂
) equal to (0°, 20°), (20°, 0°), (30°, 40°), and (40°, 30°), respectively. Then, these RAs were fabricated and tested. The highest measured aperture efficiency of 0.45 was observed for RA_0_20 and RA_20_0 at 34.2 GHz, whereas the RA_30_40 demonstrated the lowest aperture efficiency of 0.25 at 38.2 GHz.