Dual-parameter concentric ring RA elements

Reflectarray antennas (RA) are nowadays a quite well established technology, used in several applications. Nevertheless, they still suffer for some limitations, that are partially due to their intrinsic reduced bandwidth, that could be enlarged, but generally with a drastic increase of the structure complexity. Here we propose a new type of re-radiating element, consisting in two concentric square rings in which two geometric parameters are varied. In this way it is possible to better control both the spatial and frequency phase variation of the re-radiated field. Numerical analysis of reduced size RAs has been carried out, and it confirms the promising characteristics of such radiating elements.