Theory of the Suppressed-Rotation Reciprocal Ferrite Phase Shifter

A theory for the Reggia-Spencer reciprocal ferrite phase shifter is presented which explains the characteristic behavior of this device in terms of a nonreciprocal coupling of cross-polarized waveguide modes. The dominant mode is a distorted TE₁₀-like mode similar to that of a dielectric slab-loaded waveguide. The cross-polarized mode is a hybrid mode which is below cutoff. If this mode propagates, Faraday rotation occurs. The boundary value problem for these modes, in a ferrite described by a scaIar, frequency-dependent permeability, is solved and theoretical design data is presented. The frequency-dependence of phase shift and the onset of Faraday rotation is predicted and compares well with experimental results.