Multibeam Reflectarrays in Ka-Band for Efficient Antenna Farms Onboard Broadband Communication Satellites +
Footnote †: This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license ([[https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/)]([https://creativecommons.org/licenses/by/4.0/](https://creativecommons.org/licenses/by/4.0/))). [PERSON]  
1 Information Processing and Telecommunications Center, Universidad Politecnica de Madrid, 28040 Madrid, Spain; [EMAIL_ADDRESS]  
2 Area of Signal Theory and Communications, Universidad Rey Juan Carlos, 28942 Madrid, Spain; [EMAIL_ADDRESS]  
3 AtlanTTic Research Center, Universidade de Vigo, 36310 Vigo, Spain; [EMAIL_ADDRESS] (Y.R.-V.); [EMAIL_ADDRESS] (A.P.) 4 Correspondence: [EMAIL_ADDRESS]  
5 This paper is an extended version of the paper entitled \"Advanced Reflectarray Antennas for Multispot Coverages in Ka Band\" presented at the 2020 International Workshop on Antenna Technology (iWAT 2020). [PERSON]  
1 Information Processing and Telecommunications Center, Universidad Politecnica de Madrid, 28040 Madrid, Spain; [EMAIL_ADDRESS]  
2 Area of Signal Theory and Communications, Universidad Rey Juan Carlos, 28942 Madrid, Spain; [EMAIL_ADDRESS]  
3 AtlanTTic Research Center, Universidade de Vigo, 36310 Vigo, Spain; [EMAIL_ADDRESS] (Y.R.-V.); [EMAIL_ADDRESS] (A.P.) 5 This paper is an extended version of the paper entitled \"Advanced Reflectarray Antennas for Multispot Coverages in Ka Band\" presented at the 2020 International Workshop on Antenna Technology (iWAT 2020). [PERSON]  
1 Information Processing and Telecommunications Center, Universidad Politecnica de Madrid, 28040 Madrid, Spain; [EMAIL_ADDRESS]  
The generation of the multispot coverage from the satellite is typically accomplished by using four multi-fed single offset reflectors operating by a single feed per beam (SFPB) architecture [3; 4]. Reflectors offer a reliable and simple operation; however, they cannot generate the beams with an angular separation between adjacent beams as small as required for this application, since overlapping feeds would be required. Thus, four multi-fed reflectors are usually employed onboard the satellite, where each reflector produces all the beams in a specific frequency and polarization, which are spatially isolated from each other. In this way, each reflector generates the beams associated to one color in a lattice of non-contiguous spots (the spots are separated by gaps that will be covered by the beams generated by the other reflectors). Therefore, the interlaced beams produced by the four reflectors form the final four-color cellular coverage of contiguous spots. Due to the severe constraints in weight and volume of satellites, the use of four reflectors can be seen as a suboptimal antenna farm. Different multibeam antenna solutions have been proposed lately to reduce the number of antennas onboard the satellite [5]. The use of lenses [6] or array antennas [7] reduces the radiation efficiency and increases the complexity of the antenna architecture, while the highly oversized reflector proposed in [8] comprises a prohibitive stowage volume. In this paper, four different multibeam antenna solutions are proposed based on reflectarray antennas [9], following the study introduced in [10]. Each multibeam reflectarray is intended to generate half the required multispot coverage, making it possible to reduce the number of antennas onboard the geostationary satellite from four reflectors to two reflectarrays. The antenna specifications commonly required in real scenarios (described in Section 2) will be used to analyze the performance of the proposed reflectarrays. In Section 3, a 1.8 m flat reflectarray and a 1.8 m parabolic reflectarray will be proposed to generate a four-color coverage only for the transmission link with a single antenna aperture.