New bifocal design method for dual reflectarray configurations with application to multiple beam antennas in Ka-band

This contribution describes a new design technique for multi-beam dual reflectarray antennas with applications in multi-spot satellites. The bifocal design concept has been used to obtain closer beams than in a single focused antenna and, at the same time, to provide an improved performance for the off-axis beams. The required bifocal phase-shift distributions are first obtained with the two reflectarrays in parallel planes, and then adjusted to compensate the tilting of both reflectarrays in the final Cassegrain configuration. The simulated radiation patterns have been first calculated in the principal planes for the beams generated by the feeds at the two foci, and then, the multi-beam performance of the antenna has been evaluated