Development of dual-band circularly polarised reflectarray

The development of a dual-band circularly polarised microstrip reflectarray in Ka-band is presented and various reflectarray configurations with different cell elements are introduced. Among these, reflectarrays with separate crossed dipoles or orthogonal nonintersecting dipoles etched on the same or different substrate interfaces were investigated theoretically and experimentally. Adjusting the lengths of the orthogonal dipoles or arms of the cross dipoles was used to maintain 90/spl deg/ relative phase shift between the orthogonal components of reradiated fields and this gives rise to the realisation of a reflectarray that converts the linearly polarised incident field of the feed into an outgoing circularly polarised field. Various realisations of reflectarrays in terms of cell elements and configuration were designed, fabricated and tested. Measurement results for the final prototype that was of superior performance compared to the other prototypes demonstrated 36% aperture efficiency and axial ratio better than 2.0 dB, for 3% bandwidth on both the Tx and Rx bands.