Millimeterwave Tests on Passive Components of PLANCK-LFI

PLANCK [1] is the ESA mission devoted to Cosmic Microwave Background (CMB) to be launched in 2007. After COBE and WMAP pioneering work, PLANCK is designed to measure the anisotropy spectrum to the full extent of cosmological relevance and make quantitative measurements of CMB polarization. Its optical system will consist of a Gregorian telescope coupled with two instruments on the focal surface: the High Frequency Instrument (HFI) [2], an array of bolometers covering the spectral range from 84 GHz to 1THz; and the Low Frequency Instrument (LFI) [3,4], an array of pseudocorrelation radiometers spanning the range from 27 to 77 GHz in three 20% frequency bands. We measured vector patterns and return loss of feedhorns and S parameters of OMTs and waveguides, obtaining good agreement with the very demanding design specifications.