Measurements of Beam Pattern Perturbation in Corrugated Feed Horn Arrays for CMB Observations

An experimental study on the perturbation of the angular response of aW-band corrugated horn produced by nearby feeds, reproducing a typical situation of multi-feed arrays commonly used in high sensitivity Cosmic Microwave Background instruments, is reported in this paper. The effects for different positions of the scattering horn in the two principal polarisation planes were measured. We analyze the effects on both the side-lobe level and on the main beam. In particular, these results allowed us to validate design criterion for the multi-frequency focal array of the ESA PLANCK mission.