THE MICROWAVE GYRATOR 



25 



The "active" element of the device, the fenite cylinder, has been 

 termed a "Faraday Plate." 



As was pointed out earlier, the fundamcMital property of the gyrator 

 is the 180° phase difference introtluced Ix^tween the two directions of 

 propagation through it. Thus the gyrator may be thought of as a four 

 terminal circuit element having no phase shift for one direction of trans- 

 mission, and having a 180° phase shift for the opposite direction of 

 transmission. A convenient circuit symbol for the gyrator, which indi- 

 cates this property, is shown in Fig. 12. 



If the rectangular waveguides on each side of the Faraday Plate are 

 rotated about their common axis so as to make an angle of 45° with 



77- 



Fig. 12 — Circuit symbol for gyrator. 



-b 



FARADAY 

 PLATE 



POLARIZATION CIRCULATOR 



CIRCUIT SYMBOL FOR 

 POLARIZATION CIRCULATOR 



Fig. 13 — Schematic diagram of polarization circulator. 



each other, then a one-way transmission system can be created which 

 is similar to Lord Rayleigh's one-way transmission system of optics, but 

 with the important difference that this one-way transmission system 

 does not depend upon frequency but is broad band. This one-way trans- 

 mission system can be used, for example, to isolate the generator or 

 detector from the waveguide in microwave systems. In this application 

 it has the great advantage over the attenuators which are presently 

 used for this purpose in that it can be made practically lossless for the 

 direction of propagation which is desired but the reflected wave will be 

 completely absorbed and hence more complete isolation can be effected. 

 A more complex and more usefid circuit element, than this simple 

 one-way transmission property would at first indicate, is obtained by 

 adding a second connection on each side of the 45° Faraday Plate. It is 

 suggested that this device be called a polarization circulator. Thus, the 



