A Dual-Band Dual-Circularly Polarized Reflectarray for K/Ka-Band Space Applications

Reflectarrays (RAs) offer low-cost and low-profile solutions for reflector antennas that are polarization and frequency selective. These features augment their capabilities for point-to-point communications compared to conventional reflectors. Here, a dual-band dual-circularly polarized (CP) RA that can radiate independently shaped beams in the desired directions for each polarization in each band is proposed. The RA is composed of a dual-band dual-linearly polarized (LP) RA and a dual-band LP-to-CP polarizer. The proposed RA can be employed to reduce the number of the required apertures for a four-color multiple spot beam coverage implemented using a single-feed-per-beam configuration from four to two. The underlying unit cell of the proposed RA is designed for 18.3-18.8 GHz and 27.0-27.5 GHz. It provides a 323 degrees phase shift in the lower band and 381 degrees phase shift in the higher band while maintaining a cross-polarization level better than 15 dB in both bands and excellent decoupling between the two bands. An offset-fed RA is designed, fabricated, and measured.