Effects of Zero Ferrite Permeability on Circularly Polarized Waves

Experimental data is presented describing the propagation characteristics of ferrites in the vicinity of zero permeability as seen by a wave which exhibits a positive sense of circular polarization of its microwave H vector. Deailed results derived in the 9000-mc region are given for a ferrite rod axially located in circular waveguide in which the TE11, circularly polarized mode is propagating. A theoretical treatment is also presented which predicts that the behavior of a ferrite rod so located in circular waveguide and biased to the zero permeability region can be made to expel practically all microwave energy from its interior. Experimental results verifying these predictions and an experimental setup used in obtaining a portion of these results are presented in detail. It is shown that similar behavior near zero permeability can be obtained from ferrite rods located in rectangular waveguide. The utilization of ferrites near zero permeability to obtain large nonreciprocal attenuations is discussed for the cases of low, moderate, and high loss ferrites.