DIELECTRIC-COATED WAVEGUIDE 



1265 



UJ 



U 



UJ 

 Q 



I.O 

 0.8 



0.6 

 0.4 



to 

 (/) 



o 



0.2 



0.1 



0.08 



0.06 

 0.04 



0.02 



6 8 10 20 40 60 100 200 400 600 



BEND RADIUS IN FEET 



Fig. 3 — Maximum conversion loss of the TEoi wave in a vmiform bend of the 

 dielectric-coated waveguide. 2a = 2 inches; X = 5.4 mm; e = 2.5. 



There are two different applications of the dielectric-coated guide, 

 which require different designs: 



1. Intentional bends 



These are relatively short sections and the increase in TEoi attenuation 

 is usually small compared to the bend loss. Also, a high spurious mode 

 level can be tolerated, because with a mode filter at the end of the bend 

 we can always control the spurious mode level. Consequentlj^, the only 

 limit set for this type of bend is the mode conversion loss of the TEoi 

 wave. There is conversion loss mainly to TEn , TE12 and TMn . Increas- 

 ing the phase difference of the TMn wave by making the dielectric coat 

 thicker decreases the phase-difference between TEoi and TE12 and in- 

 creases the phase-difference between TEoi and TEu . Apparently we get 



