A Phenomenological Theory of the Reggia-Spencer Phase Shifter

The novel ferrite-actuated variable phase shifter reported by F. Reggia and E. G. Spencer operates on a principle which, while resembling that of the familiar Faraday rotation devices, differs from them in a way which leads to quite different and unexpected behavior. The observed properties of the device depend on the interaction between the radiation and the ferrite taking place under several special conditions: namely, elliptic waveguide symmetry, a variation in the permeability associated with the magnetic disorder of the unsaturated ferrite, and a dielectric-waveguide effect. The essential properties of the device can be explained with the aid of a simplified model in which the radiation is represented by plane waves. The contribution of the dielectric-waveguide effect can be estimated on the basis of known solutions of a simpler problem, namely that of a dielectric rod partially filling circular guide. The model furnishes insight into the characters of the modes of propagation under conditions resembling those of the Faraday rotator but subject to elliptic symmetry and other complications.