Propagation in ferrite-filled circular waveguides

A descriptive treatment is given of the lower-order ferrite-filled circular waveguide modes in terms of the bi-refringent character of the propagation. It is shown that under suitable conditions of d.c. magnetization the ferrite-filled guide can only support certain modes when its radius is less than a given value. These inverse cut-off modes are investigated in some detail, it is shown that their group velocity is negative and typical field patterns are illustrated. Experimental results are presented which confirm the major points of the theory and show reasonable quantitative agreement.