Dual-frequency Reflectarray Cells to Generate Closely Spaced Beams in Orthogonal Circular Polarization

A dual-frequency reflectarray cell is proposed in this work to provide a progressive phase shift of opposite sign in each circular polarization (CP), by applying a variable rotation technique (VRT) [1]. The proposed reflectarray cell consists of two symmetrical arcs printed on the top surface and two orthogonal sets of parallel dipoles printed on two levels of a grounded dielectric substrate, see Figure 1. The arcs and dipoles are rotated independently to control the phase in CP at the lower (19.7 GHz) and higher (29.5 GHz) frequencies respectively. This reflectarray cell can be used to generate two adjacent beams in orthogonal CP per feed at transmission (Tx) and reception (Rx), in order to reduce the number of feeds and antennas required in current multi-spot satellites operating in Ka-band, as proposed in [1] for a single frequency band.