Bifocal Dual-Reflectarray Antenna to Generate a Complete Multiple Spot Beam Coverage for Satellite Communications in Ka-Band

This paper presents a novel multibeam transmitting dual-reflectarray antenna able to generate a complete multiple spot coverage from a geostationary satellite in Ka-band (20 GHz). The bifocal design technique has been exploited for the first time to reduce by 50% the beam deviation factor with respect to the equivalent monofocal antenna, allowing to produce adjacent beams separated by only 0.56° in the antenna offset plane. In order to guarantee an acceptable spillover, the main reflectarray has been oversized in the same plane where the beams are compressed, resulting in an elliptical reflectarray of 3.5 m × 1.8 m. The interleaved beams required to provide the complete multi-spot coverage are produced in the orthogonal polarization, using the same aperture and feeds. The proposed antenna requires a smaller main aperture (about half of the area) and a lower number of feeds than other configurations that use a single oversized reflector to generate a complete multi-spot coverage, showing promising results for communication satellite applications in the Ka-band.