Folded multilayer microstrip reflectarray with shaped pattern

A folded multilayer printed reflectarray with shaped pattern is demonstrated. The configuration consists of a multilayer twister reflectarray, a centered feed embedded in its structure and a polarizing grid, which acts as reflector and radome for each polarization, respectively. A design procedure, valid for obtaining any arbitrary shaped pattern, has been implemented. In order to achieve the pattern specifications along a frequency band, initially a multifrequency pattern synthesis method, which relies on a phase-only synthesis, is applied to obtain the required phase-shift on the reflectarray surface. Afterwards, each stacked patch is individually optimized to generate the required phase-shift previously synthesized. The method has been successfully applied to a LMDS base station antenna, characterized by a sectorial cosecant squared beam in the band 24.5-26.5 GHz. A breadboard consisting of a folded 3-layer circular reflectarray is presented. Measurements show a good concordance with theoretical patterns at 25 GHz, and good shaping of the beam along 24-26 GHz.