16 THE BELL SYSTEM TECHNICAL JOURNAL, JANUARY 1952 



9,000 megacycles, 



4Filf.7 ^ 2000 X 17.6 X 10^ _ ^ ^ . . 



CO - 9000 X 27r X 10« ' '^^ ^ ^ 



Hence, the following approximation will be valid to within 5 per cent. 



With this approximation, Equation (23) reduces to: 



Equation (25) is quite remarkable. Not only does it predict large 

 rotations, but it also predicts that, within the above approximations 

 the rotation will not depend upon the frequency of the incident radia- 

 tion. For the assumed values, 



8' = 15 



e" = 



47rM, = 1000, 



Equation (25) predicts rotations of, 



- = 65°/cm. 



DESCRIPTION OF EQUIPMENT AND MEASURING TECHNIQUES 



The Faraday rotation has been measured in a large number of ferrites 

 in order to verify the above theory and in an effort to improve the 

 characteristics of the microwave gyrator. A diagram of the experimental 

 equipment is given in Fig. 5, and a diagram of the test chamber in which 

 the rotations were measured is given in Fig. 6. In the test chamber, 

 two rectangular waveguides are separated by a circular waveguide, 

 the proper nonreflective transitions being made at each end of the 

 circular section, which is about twelve inches long. One rectangular guide 

 is supported so that it can be rotated about the longitudinal axis of the 

 system. The dominant TEw mode is excited in one rectangular guide, 

 and by means of the smooth transition this goes over into the dominant 

 TEn mode in the circular guide. The rectangular guide on the opposite 

 end will accept only that component of the polarization which coincides 

 with the TEio mode in that guide, the other component being reflected 



