Broadband Reflectarray Antenna on a Periodically Perforated Substrate

We propose a broadband single-layer reflectarray antenna constituted of a double-screen metallic grating on a periodically perforated low-cost substrate. The reflection characteristics of this structure are computed with a full-wave computational technique that utilizes the dyadic Green's function evaluated by an equivalent transmission line modeling in the spectral domain. The obtained dyadic Green's function is then used in an integral equation for the induced surface current densities on the metallic gratings. The resulting integral equation is solved by the Galerkin's method of moments with subdomain basis functions. With the help of this semianalytical method, the phase diagram of the reflectarray unit cell is computed. Using the calculated phase diagram, a center-fed reflectarray is designed at a center frequency of 10.5 GHz. To validate the numerical results, the designed reflectarray for the X-band (8.95-12.1 GHz) is fabricated and measured. The measurements on a 270 mm x 270 mm and F/D = 0.95 reflectarray show a maximum gain of 26.57 dBi with a 1-dB gain bandwidth of 29.5% and an efficiency of 41% at 10.5 GHz. It is shown that the fabricated reflectarray exhibits a reduced radar cross-section outside its operating bandwidth.