Design of a 2-bit dual-polarised unit-cell for reflectarray applications

We introduce here a new configuration of cross-dipole dual-polarised unit-cell for reflectarray applications. This cell is integrated inside a metallic square waveguide. The layout is compatible with the integration of p.i.n. diodes. As a proof of concept, we only consider ideal cases where the on and off states of the diodes are represented by ideal short circuits and open circuits, respectively. The design methodology and unit-cell performance are described. A passive bredboard has been designed and measured at 8.2 GHz. The numerical results given in X-band show that, for each polarisation, the equivalent bit resolution reaches nearly 2 bits when using three diodes per dipole. Furthermore the isolation between orthogonal polarisation is insured by cell symmetries.