Broadband microstrip reflectarray with multiple-resonance dipoles

Based on three different substrates, the phasing characteristics of a two-resonance element for use of a single layer microstrip reflectarray, which is consist of two bended dipoles, is investigated. It is shown that composite substrate with thick foam features low slope over broadband, while the range of the phase is exceed 360°. Compared with two layers reflectarray, similar result is obtained using structure in the paper. Then, a modified unit cell and its phasing characteristic are given, which indicate approximately accordant phase shift curves over 6-10GHz. Using this element, a 20° beam steering reflectarray operating at 8GHz is designed. The computed results demonstrate that 1-dB gain bandwidth close to 50% is obtained.