This contribution describes the design of a multibeam parabolic reflectarray to produce two adjacent beams per feed in orthogonal Circular Polarization (CP) simultaneously at transmit (Tx) and receive (Rx) frequencies in Ka-band. The Variable Rotation Technique (VRT) has been applied to reflectarray cells based on two types of resonant elements, which makes it possible to provide orthogonal beams at Tx and Rx, as well as to implement an in-band optimization procedure to reduce the cross-polarization. A 90-cm parabolic reflectarray has been designed, manufactured and tested to produce multiple adjacent beams in RHCP and LHCP at both 20 and 30 GHz. The results are satisfactory and validate the concept of generating two spaced beams in orthogonal CP by a single feed, changing the polarization of the beam between Tx and Rx. This concept can be suitable for multispot satellites in Ka-band, enabling to halve the number of onboard antennas and feeds.

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This paper presents some recent developments in multiple beam antennas (MBAs) based on reflectarrays for communication satellites in K-and Ka-bands. The existing high throughput satellites commonly employ four reflector antennas to provide cellular coverage formed by multiple spot beams in a four color scheme. Reflectarray antennas are proposed as an attractive solution for the design of novel MBA configurations to produce multi-spot coverage with a smaller number of apertures than conventional MBA systems based on reflector technology. Single and dual reflectarray configurations have been considered for this purpose, exploiting the reflectarrays' ability to produce independent beams in different polarizations and frequencies.

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