Low-Loss Modes in Dielectric Lined Waveguide

T h e possibility of using a circular electric ( T E 0 i ) mode in circular waveguide has been of considerable interest since t h e initial discovery of its desirable low-loss characteristics (in the following, we are concerned only with t h e heat loss in t h e guide). One t y p e of guide currently u n d e r consideration (Fig. 11 consists of a highly conducting outer wall to which a thin dielectric liner is bonded to b r e a k the degeneracy i n phase velocities for the TE,,i a n d T M n modes i n metallic circular waveguide. T h e circular electric mode loss characteristics of t h i n l y lined circular waveguide h a v e been determined by H. G. Unger. 1 - 3 T h i s work has 1631 1632 THE BELL SYSTEM TECHNICAL JOURNAL, M A Y - J U N E 1971 Fig. 1--Dielectric lined circular waveguide. s i n c e been e x t e n d e d 4 a n d i t w a s f o u n d t h a t o t h e r m o d e s a l s o h a v e verylow h e a t loss o v e r a n a p p r e c i a b l e f r e q u e n c y r a n g e . A f u l l s c a l e d i s c u s sion of t h e a n a l y s i s is b e y o n d t h e scope of t h i s p a p e r b u t will be a v a i l able in a forthcoming paper.4 In t h e following, the analytical app r o a c h i s i n d i c a t e d a n d s o m e t y p i c a l r e s u l t s f o r t h e h e a t loss ( c o p p e r a n d d i e l e c t r i c loss) o f t h e T E m , T E f l 2 , a n d T M 0 2 m o d e s i n lined circular guide are given.