Dual-Band Reflectarray to Generate Two Spaced Beams in Orthogonal Circular Polarization by Variable Rotation Technique

This contribution describes the design of a reflectarray to produce two adjacent beams per feed in orthogonal circular polarization (CP) simultaneously at transmit (Tx) and receive (Rx) frequencies in the <italic>Ka</italic> band. The discrimination in CP is achieved by the variable rotation technique (VRT), whose dual band operation is validated for the first time by the manufacture and measurement of a 25 cm <inline-formula> <tex-math notation="LaTeX">$\times \,\, 25$ </tex-math></inline-formula> cm reflectarray demonstrator. Moreover, an optimization procedure has been implemented to improve the narrowband performance of the VRT (which leads to high cross-polar levels when the VRT is applied). The reflectarray prototype has been designed to deviate by ±5° the beams radiated by a dual-CP feed-horn at Tx and Rx frequencies in the <inline-formula> <tex-math notation="LaTeX">$Ka$ </tex-math></inline-formula> band (20/30 GHz). The results are satisfactory and validate the concept of generating two spaced beams in orthogonal CP and dual band by the VRT with a single feed. This concept can be suitable for multiple spot satellites in the <inline-formula> <tex-math notation="LaTeX">$Ka$ </tex-math></inline-formula> band, enabling a reduction in the number of antennas and feeds needed to provide the multispot coverage.