Abstract: The invention relates to a phase shifting device for switching the polarization state of an electromagnetic wave. Two waveguide sections have an exterior rectangular opening defined in their end surfaces. A dielectric break is situated substantially collinearly with the longitudinal axis of the waveguide in substantially a center of the waveguide. In one embodiment, a central structure includes a cylinder having a permeability greater than that of a vacuum, and having two substantially circular end faces situated in perpendicular orientation to a longitudinal axis of the cylinder and two dielectric cones. A magnetic field source switches a polarization of the electromagnetic wave causing a phase shift of the electromagnetic wave of substantially zero degrees when the controllable magnetic field is off and a pre-determined phase shift when the controllable magnetic field is on. The invention can be used in an interferometer apparatus and a phased array apparatus.