Design of Cassegrain reflectarray antenna with compact ring focus feed

A Cassegrain reflectarray antenna using compact ring focus feed is introduced in this paper. The ring focus is formed by the dielectric guide sub-reflector, where the impedance matching can be achieved by adjusting the dimension of the dielectric guide. Also, the actual incidence angles of the coming waves are considered in the design of the reflectarray. A 572-element Cassegrain reflectarray with a low focus-to-diameter rate (F/D) of 0.2 has been designed and simulated. The numerical results demonstrate that this flat Cassegrain reflectarray has achieved aperture efficiency of 33.3% at 12GHz.