Thin microwave phase-shifting surface lens antenna made of square elements

A 90?? phase-correcting Fresnel zone plate (FZP) antenna has been realised at 30??GHz using a thin three-layer microwave phase-shifting surface (PSS) with square conducting shapes as the unit cell elements. These square elements allow dual-polarisation or circular-polarisation capabilities, which could not be achieved by the previously reported PSS structures the unit cell elements of which were strip-based. This new PSS lens was compared with the previously reported strip-element version. The square element PSS lens has slightly higher gain, but a small degradation to cross-polarisation level and gain bandwidth. The effect of altering the roll angle of the lens with the feed kept fixed was also investigated. This revealed that gain bandwidth is unchanged, but there is a marginal gain degradation and increase in the cross-polarisation level (albeit still well within an acceptable range) for certain roll angles.