Phasing characteristics of variable size double rings of square or circular shape for design of a single layer microstrip reflectarray

The paper reports on the investigations into phasing characteristics of a unit cell of a single-layer microstrip reflectarray including variable size double rings of square or circular shape. It is shown that if the rings are printed on a conventional dielectric substrate, the phasing characteristics of the unit cell exhibit the phase range well in excess of 360deg but with a sharp slope. By printing the double ring elements on a thick composite substrate formed by a thin laminate and thick foam a slower slope and a reduced range but still covering 360deg can be obtained. The use of such a unit cell can lead to a wideband design of a single layer microstrip reflectarray.