10-16] MICROWAVE FERRITE DEVICES AND THEIR APPLICATION 561 



Switches. There are numerous ways in which ferrites can be used for 

 microwave switching. For example, reversing the direction of the magnetic 

 biasing field applied to a circulator will reverse the direction of circulation 

 in the device (i.e. the direction of the arrow in Fig. 10-33 reverses with 

 direction of applied field). In this manner a four-port circulator can be used 

 as a reversing switch for such applications as lobe switching. 



A solenoid-controlled 90° Faraday rotator can be used to switch an input 

 signal between two orthogonal output ports of a dominant mode circular 

 waveguide. With a slightly different geometry, a reversible 45° rotator can 

 accomplish the same thing. The first switch type is bidirectional, but has 

 the property of a gyrator when the magnetic field is applied. The second 

 type functions as a reversible three-port circulator and as such is not 

 bidirectional. It should be evident that in applying a ferrite component 

 it is important to consider whether or not it is a reciprocal device. Fig. 

 10-35 shows an experimental four-port reversible ferrite switch which is 



Fig. 10-35 Experimental Model of a Four-Port, Reciprocal Ferrite Switch. Two 

 Faraday Rotation Gyrators are Used, and Switching is Accomplished by Reversing 

 the Current in One of Them. (U.S. Naval Reasearch Laboratory.) 



reciprocal, and consequently bidirectional. Two 90° Faraday rotators are 

 used with two magic-tee hybrids in a symmetrical bridge circuit. Switching 

 is accomplished by electronically reversing just one of the 90° rotators. The 



