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 Ka 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 x 25 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 degrees the beams radiated by a dual-CP feed-horn at Tx and Rx frequencies in the Ka 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 Ka band, enabling a reduction in the number of antennas and feeds needed to provide the multispot coverage.