Deep space antenna for Rosetta mission: design of the S/X band dichroic mirror and analysis of the beam waveguide

The design of a dichroic mirror operating in S/X band for the Rosetta mission is described. In order to achieve the required performance, a trade-off between electrical and mechanical problems was necessary. So the shape of the holes in the dichroic plate was chosen according to good electrical performances in terms of cross-polar level and insertion losses and to acceptable mechanical deformations of the plate itself. Furthermore, a sample of the designed perforated mirror was manufactured and measured in an anechoic chamber. Software (GRASP8) simulations evaluated the impact of the dichroic plate on the electrical performances of the beam waveguide feeding the shaped Cassegrain antenna.