On Radiation Performances of Reflectarray Antennas Constructed With Subwavelength Unit Cells

Multi-element approach is utilized to increase the phase variation range of a square-ring subwavelength unit cell (UC) from 313
^°
to more than 560
^°
. Radiation characteristics of three thin reflectarray antennas (TRAs) constructed with the proposed UCs are investigated. This investigation demonstrates that to achieve a broadband highly efficient TRA, the employed λ/ 5 - UC must have reflection loss considerably less than 0.1 dB and its constructing elements should also scatter the incident fields in the same fashion, i. e., the current distributions of all parts of the multi-element UC are of the same shape and co-phased.