Design of a CPSS-based reflectarray cell with controllable reflected phase for dual-circularly-polarised reflectarrays

A first step towards the design of dual-circularly polarised reflectarrays with independent control of both polarisations is proposed in X-band. A reconfigurable unit-cell based on a circularly- polarised selective surface is studied at 8.5 GHz. It provides a 2-bit phase resolution in reflection for the left hand circular polarisation (LHCP) and is nearly transparent in right hand circular polarisation (RHCP). The simulated characteristics are excellent over a 6.4% bandwidth. The proposed unit-cell is fabricated using stacked substrates. A loss budget demonstrates that loss is quite balanced between loss in materials and polarisation conversion. Then, a study of the effect of realistic switches is shown in order to demonstrate that conventional p.i.n. diodes would cause an acceptable loss increase.