10-16] MICROWAVE FERRITE DEVICES AND THEIR APPLICATION 



10-16 MICROWAVE FERRITE DEVICES AND THEIR 

 APPLICATION 



557 



The solid-state materials are certain to play major roles in future micro- 

 wave systems. Currently, the new microwave jerrite devices*'^ are causing 

 a near revolution in microwave system concepts through application of 

 nonreciprocal properties and rapid electronic control to microwave cir- 

 cuitry. The ferrites, ceramic-like ferromagnetic semiconductor materials, 

 when magnetically biased exhibit unusual microwave permeability charac- 

 teristics due to mutual interaction of the magnetic fields with certain 

 electrons of the ferrite. 



For the special case of circularly polarized waves, the microwave perme- 

 ability of the ferrite is a scalar quantity and is different for opposite senses 

 of circular polarization. The manner in which the microwave permeabilities 

 vary with magnetization of the ferrite is shown in Fig. 10-29. Note that for 

 the positive sense of circular polarization, the permeability, starting at 

 unity in the unmagnetized state, decreases, passes through zero, and then 

 becomes negative. At a certain value of magnetization, which is propor- 



500 



1000 1500 2000 2500 3000 

 MAGNETIC FIELD IN OERSTEDS 



3500 4000 



Fig. 10-29 Real Part of the Effective Permeability of a Ferromagnetic Medium 



Which Is Magnetized Parallel to the Direction of Propagation of an Infinite Plane 



Wave. (Courtesy of C. L. Hogan. Reprinted from Reference 48 by permission of 



The Institute of Radio Engineers). 



^''See particularly the Ferrites Issue, Proc. IRE 44, No. 10 (October 1956). 



