A Novel Single Layer Wideband Reflectarray Design Using Two Degrees of Freedom Elements

A broadband linearly polarized single-layer reflectarray antenna constructed with element cells of spiral-dipoles is presented in this communication. The proposed method achieves the phase change requirements by continuously adjusting the two degrees of freedom (TDF) elements. Then, a linear and smooth phase response covering 360° is obtained by adjusting the TDF. Furthermore, by introducing four rectangular rings around the spiral-dipoles, a relatively slow phase change slope can be obtained and the maximum differences between the achieved phase acquired by element and ideal phase at 6.5 and 9.5 GHz are 20° and 58°, respectively, enlarging the operating bandwidth. A reflectarray prototype with a rectangular aperture of 300 mm in diameter is designed, fabricated, and experimentally verified. The results include a measured gain of 26.5 dBi at 8 GHz with an aperture efficiency of 55%; the 1 dB gain bandwidth can reach 35%. The proposed structure can be extrapolated to higher frequencies due to its single-layer performance. Its benefits include a reduction in manufacturing costs and the mitigation of alignment errors.