Unit Cell for Reflectarrays Operating With Independent Dual Circular Polarizations

A unit cell for dual-circularly-polarized (CP) reflectarrays illuminated by a dual-CP primary feed is designed and validated experimentally around 8.5 GHz. It is composed of two layers reflecting independently and simultaneously the two incident circular polarizations. The first layer is a circular polarization selective surface (CPSS) based on an enhanced version of the original Pierrot's cell with multiple wires bent in a crank-like shape. The second layer is made of dipoles printed on a grounded substrate; it is used to reflect the incident right-hand CP (RHCP) wave transmitted through the CPSS with a 2-bit phase resolution. This letter demonstrates that the sole association of both layers is not sufficient to reach the expected behavior. An additional optimization step is required to cancel out uncontrolled reflections and improve isolation between both polarizations. The simulated and measured characteristics are in good agreement for the two circular polarizations.