546 ANTENNAS AND RF COMPONENTS 



a microwave transmission line. Pressurization has become an important 

 factor in the reHabiUty of airborne radar systems, for seal rupture could 

 completely disable a system at high altitude. Dielectric-filled waveguides, 

 proposed as a solution to the problem, are under development.^^ 



10-15 MISCELLANEOUS MICROWAVE COMPONENTS 



As the elements which compose microwave assemblies and systems, 

 microwave components encompass many forms and functions. Certain 

 components serve only to change transmission line direction, while others 

 perform some transformation of the electrical description of the propagated 

 wave. A limited number of the more important components will be 

 discussed. The reader is urged to consult the references and bibliography 

 for greater coverage of this extensive topic. 



Bends, Twists and Rotary 

 Iw ^- Joints. The compactness required of 



airborne systems may invite generous 

 use of waveguide bends. As pointed 

 out earlier in this chapter, in the 

 interest of broadband performance, 

 their number should be kept to a 

 minimum, as each will introduce a 

 finite reflection. Whether a long, 

 fabricated bend is better than a com- 

 pact, die-cast bend will depend more 

 4 &:A^ °" ^^^ relative quality of the com- 



^^^ '*** ponents than on the radius of the 



"*• bend. At slight disadvantage re- 



flectionwise, the precision-cast bends 



permit very direct and abrupt 



changes in waveguide direction. 



Fig. 10-18 Waveguide 'Twist-Turn'' ^^^ ^^^^j component shown in 



Simultaneously Executes 90 1 wist and -^. ,^,n n i 



90° Turn. (Kearfott Company, Inc., Fig. 10-18, called a twist-turn, 



Western Division) simultaneously executes a 90° twist 



and a 90° bend. 



Waveguide twists often are fabricated from a portion of the waveguide 



run by relatively simple shop techniques. This results in a rather long 



section of waveguide devoted to the twist. A significant reduction in length 



is possible using step-twist techniques.^" Very effective wideband step 



29Tore N. Anderson, "Practical Dielectric Filled Waveguide," IRE Trans. MTT-3, No. 2, 

 82-86 (March 1955). 



30H. A. Wheeler and H. Schwiebert, "Step Twist Waveguide Components," IRE Trans. 

 MTT-3, No. 5, 44-52 (October 1955). 



'^Eft^ 



