Theory of ferrites in rectangular waveguides

Reciprocal and nonreciprocal propagation of electromagnetic energy in an infinitely long rectangular waveguide partially filled with one or two ferrite slabs is described.Methods for obtaining exact solutions of the transcendental equations usually encountered in these boundary value problems are demonstrated for several structures. Calculations are carried out for a lossless ferrite and the phase constant is plotted as a function of the ferrite slab thickness. The cutoff conditions for the lowest TE mode are evaluated in terms of the ferrite slab thickness. New modes, not associated with the empty waveguide modes, are analyzed as ferrite dielectric modes, their propagation characteristics are discussed and the rf electric and magnetic field patterns are plotted. The rf electric fields are plotted for all reciprocal and nonreciprocal modes and the appropriate field configurations are used to explain the operation of ferrite cutoff isolators, the field-displacement isolator, the field-displacement circulator, and the nonreciprocal phase shifter. Solutions above ferromagnetic resonance are shown and the -fields are plotted. A brief comparison of the operation of dispersive devices at high and low frequencies is made. The calculations are extended to include absorption loss, and nonreciprocal attenuation is plotted as a function of slab position near resonance.