A unit cell waveguide approach to designing multi-layer reflectarrays of variable size patches

An equivalent unit cell waveguide approach (WGA) to designing a multi-layer microstrip reflectarray of variable size patches is presented. In this approach, a normal incidence of a plane wave on an infinite periodic array of radiating elements is considered to obtain reflection coefficient phase curves for the reflectarray´s elements. Based on this approach, a fast computer algorithm is developed to generate reflection coefficient phase curves for a multi-layer microstrip patch reflectarray. The validity of the developed algorithm for obtaining elements phase curves is tested against other alternative approaches. Having confirmed the validity of the WGA approach, a small offset feed two-layer microstrip patch array is designed and developed. This reflectarray is tested experimentally and shows good performance.