A perturbation method for circular waveguides containing ferrites

The paper describes a perturbation method which enables the propagation coefficient of a circular waveguide, containing a longitudinally magnetized ferrite, to be determined over a wider range of parameters than hitherto. The method relies on the fact that, when a mode, propagating in a circular waveguide containing a longitudinally magnetized ferrite rod, is circularly polarized on the waveguide axis, the field throughout the whole of the ferrite is nearly circularly polarized. Theoretical and experimental results for the negative circularly polarized dominant mode are favourably compared in the case of a Ferroxcube B2 ferrite.