Design of Dual-Band Dual-Polarized Reflectarray for Future Multiple Spot Beam Applications in Ka-band Min Zhou 1 , Stig B. Sørensen 1 , Niels Vesterdal 1 , Michael F. Palvig 1 , Yan Brand 2 , Simon Maltais 2 , Jordan Bellemore 2 , and Giovanni Toso 3 1 TICRA, Copenhagen, Denmark, mz@ticra.com 2 MDA, Ste-Anne-de-Bellevue, Quebec, Canada, Yan.Brand@mdacorporation.com 3 ESA, ESTEC, Noordwijk, The Netherlands, Giovanni.Toso@esa.int Abstract—The design of a parabolic polarization selective reflectarray for dual-band dual-circular polarization for multiple beam applications in Ka-band is presented. The reflectarray has a diameter of 0.65 m and is a single-layer design consisting of rotated split hexagonal-loop dipole elements. For RHCP, the reflectarray scans the reflected beam half a beamwidth in one direction, and for LHCP, the reflectarray scans the reflected beam half a beamwidth in the opposite direction. This is achieved in both Tx (19 GHz) and Rx (29 GHz). Using a feedarray of 27 feeds, 54 beams can be generated. With this concept, a full multiple beam coverage employing the 4-color frequency/polarization re- use scheme can be covered using only two reflectarrays while maintaining the single-feed-per-beam operation. Index Terms—Reflectarrays, satellite applications, optimization I. I NTRODUCTION Multiple beam reflector antennas are becoming more and more popular for telecommunication applications due to their capability of delivering high capacity for high-throughput satellites (HTS). Currently, the state-of-the-art is to employ four dual-band (Tx/Rx) single-feed-per-beam (SFB) reflectors to cover a contiguous spot beam coverage using the 4-color re- use scheme, one reflector for each of the colors [1]. Recently, significant efforts have been made on reducing the number of main apertures onboard these HTS. The in-flight demon- stration of the MEDUSA multiple-feeds-per-beam (MFB) [2] has paved the way to cover the multiple beam coverage using only two main apertures [3]. Solutions to produce a full Tx/Rx multiple beam coverage using only one main aperture has also been suggested by combining two single-band MFB feed systems through a frequency selective sub-reflector [4]. However, despite being able to reduce the number of main apertures, MFB reflectors require advanced beam forming networks. ESA has recently promoted activities on polarizing and polarization selective surfaces [5]–[7] with the aim to reduce the number of apertures required for HTS missions while maintaining SFB operations. However, these concepts rely on the use of dual-reflector systems which increase the complex- ity of the antenna system. In [8], we proposed an innovative reflectarray concept to reduce the number of apertures, while considering a single offset antenna system and maintaining SFB operation. The idea is to use a parabolic polarization selective reflectarray that can radiate two of the beams in the 4-color re-use scheme. The two beam types shall discriminate in polarization, meaning that for one polarization, the reflectarray needs to scan the beam in one direction, and in the orthogonal polarization, the reflectarray needs to scan the beam in the opposite direction. In this way, a single reflectarray can generate two of the four colors in the 4-color re-use scheme and another reflectarray can generate the remaining colors resulting in a total of two apertures to cover the full multiple beam coverage. In [8], the concept was demonstrated for the Tx-band (20GHz) only. However, in a real Ka-band mission, the re- flectarray must operate in both Tx (20 GHz) and Rx (30 GHz) In this paper, we present the design of a Ka-band polarization selective reflectarray operating in both Tx and Rx bands. The reflectarray is based on a single-layer design and uses the variable rotation technique to control the reflection phase in Tx/Rx. As array element, the split hexagonal-loop dipole element is used and the reflectarray is designed for global coverage. II. REFLECTARRAY DESIGN Although the proposed concept has several advantages com- pared to existing solutions, there are several major challenges that need to be solved. First, the design of a dual-band reflectarray with separated beams for the two orthogonal CP is not an easy task. To fulfill the stringent RF requirements of a real flight mission is challenging and demands designs with high complexity. Second, the manufacturing of a doubly curved reflectarray is not a straightforward task as it is with planar reflectarrays. There are no standard manufacturing technologies for the production of curved reflectarrays and a first breadboard is yet to be demonstrated. Finally, once the reflectarray has been manufactured and tested, a good correlation between simulations and measurements is needed to verify the accuracy of the design and the modelling tools. 13th European Conference on Antennas and Propagation (EuCAP 2019)