1340 THE BELL SYSTEM TECHNICAL JOURNAL, NOVEMBER 1953 



<3^ 



-3 



240 



200 





•40 



160 

 120 



2000 3000 4000 5000 6000 



EFFECTIVE MAGNETIC FIELD IN OERSTEDS 



Fig. 4 — Effective permeability seen by a plane wave in a transversely mag- 

 netized infinite medium. Real part above and imaginary part below. 



absence of dielectric loss the propagation constant of the wave is given 

 by: 



/3 = w- 



^'V^ 



K^) 



(12) 



Thus a variable phase delay is obtained by controlling the magnitude 

 of the applied field. This delay is not necessarily accompanied by a change 

 in attenuation so that an ideal phase shifter can be made using this 

 effect. There are numerous other applications which can be made of the 

 longitudinal and transverse applied field phenomena. Many of these will 

 be discussed later in this article. 



LOSS MECHANISMS IN FERRITES AT MICROWAVE FREQUENCIES 



Neglecting dielectric losses, the plane wave theory predicts almost no 

 loss at all for a negative circularly polarized wave and a single absorption 

 line for a positive C.P. wave. In practice a more complicated behavior 

 is observed, and to facilitate the discussion we show in Fig. 5 typical 

 loss characteristics superposed upon the theoretical loss curve of Fig. I. 

 We will enumerate the main points of interest before proceeding with the 

 discussion. The specific differences in behavior are: 



