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

Reflectarrays (RAs) offer not only low-cost and low-profile solutions for point-to-point communications, but they also have a controllable polarization and frequency response. This property of an RA allows to realize polarization-selective and multi-band high-gain apertures. Here, we propose a novel dual-band dual-circularly polarized (CP) RA with a unique set of properties. The RA is composed of a dual-band dual-linearly polarized (LP) RA and a dual-band LP-to-CP polarizer. By dividing the CP-RA into an LP-RA and a polarizer, we obtain the ability to radiate CP shaped beams or pencil beams at desired directions for any of the dual bands and for each polarization, independently. Moreover, the polarizer has a unique property to convert an LP wave to orthogonal CP waves at the two bands. This relaxes the feed complexity and increases the out of band rejection. The underlying unit cell of the proposed RA is designed for 18.2-18.8 GHz and 27.8-28.3 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 more than 15 dB in both bands, and excellent decoupling between the two bands. An offset-fed RA is designed and full-wave simulation results are presented and confirm the performance of the proposed structure.