Design of a stacked stub-loaded patch element for X-band reflectarray antenna with true time delay

A multilayer reflectarray element consisting of a stacked stub-loaded patch is proposed for X-band linear polarization reflectarray antenna. Geometric parameters of the structure are optimized to achieve better impedance matching between the stub line and the radiating patch. Infinite array method is used for analysis of the reflectarray. The effect of oblique incidence is also investigated on the phase diagram. Obtained results show that the phase curves are nearly smooth for a wide range of phase delays that enable the true time delay effect.