Linear polarization and the effects of metal reflectors used to redirect the beam in microwave radiometers

Problems concerning the response of microwave radiometers to the polarization of incident radiation are examined. Particular attention is given to their consequences in experiments measuring the intensity anisotropy of the cosmic background radiation. Considered in detail are instrumental configurations in which metal reflectors are used to redirect the antenna beam. Some effects introduced by such reflectors are calculated and modelled for different values of some relevant parameters, in order to evaluate their contribution to instrumental errors. The analysis of a real experiment is then considered. It is shown that such mechanisms, if ignored, can seriously affect the measurements.