Millimeter Wave Passive Devices for Measurements of the Polarized Sky Emission

The polarized sky emission can be detected by measuring its Stokes parameters through a correlation unit, usually called Hybrid Phase Discriminator (HPD). In the millimeter wave range and for rather large bandwidths, heterodyne receivers are not applicable, and the correlation units have to work in the frequency band of the radiometer. The SPOrt (Sky Polarization Observatory) project will investigate the polarized radiation by means four radiometers at the frequencies 22, 32, 60 and 90 GHz within a 10% bandwidth. This contribution deals with the study of a new configuration of waveguide HPD’s that will be mounted on these radiometers. The configuration presents a high degree of sensitivity for the detection of linearly polarized radiation and is suitable for those technologies that offer a high degree of accuracy. Moreover, the set up is particularly robust with respect to the mechanical uncertainties, which are more significant in the higher frequency bands.