title: Systematic effects induced by a flat isotropic dielectric slab.
abstract: The instrumental polarization induced by a flat isotropic dielectric slab in microwave frequencies is discussed. We find that, in spite of its isotropic nature, such a dielectric can produce spurious polarization either by transmitting incoming anisotropic diffuse radiation or emitting when it is thermally inhomogeneous. We present evaluations of instrumental polarization generated by materials usually adopted in radio astronomy, by using the Mueller matrix formalism. As an application, results for different slabs in front of a 32 GHz receiver are discussed. Such results are based on measurements of their complex dielectric constants. We evaluate that a 0.33 cm thick Teflon slab introduces negligible spurious polarization (<2.6 x 10(-5) in transmission and <6 x 10(-7) in emission), even minimizing the leakage (<10(-8) from Q to U Stokes parameters, and vice versa) and the depolarization (approximately 1.3 x 10(-3)).
authors.affiliation: INAF-IASF Roma, Roma, Itlay. claudio.macculi@iasf-roma.inaf.it
authors.forename: Claudio
authors.initials: C
authors.lastname: Macculi
authors.forename: Mario
authors.initials: M
authors.lastname: Zannoni
authors.forename: Oscar Antonio
authors.initials: OA
authors.lastname: Peverini
authors.forename: Ettore
authors.initials: E
authors.lastname: Carretti
authors.forename: Riccardo
authors.initials: R
authors.lastname: Tascone
authors.forename: Stefano
authors.initials: S
authors.lastname: Cortiglioni