Helix Waveguide 



By S. P. MORGAN and J. A. YOUNG 



(Manuscript received July 23, 1956) 



Helix waveguide, composed of closely wound turns of insulated copper 

 wire covered with a lossy jacket, shows great promise for use as a communi- 

 cation medium. The properties of this type of waveguide have been investi- 

 gated using the sheath helix model. Modes whose wall currents follow the 

 highly conducting helix have attenuation constants which are essentially 

 the same as for copper pipe. The other modes have very large attenuation 

 constants which depend upon the helix pitch angle and the electrical proper- 

 ties of the jacket. Approximate formidas are given for the propagation con- 

 stants of the lossy modes. The circular electric mode important for long- 

 distance communication has low loss for zero-pitch helices. The propagation 

 constants of sotne of the lossy modes in helix waveguide of zero pitch have 

 been calculated numerically, as functions of the jacket parameters and the 

 guide size, in regions where the approximate formulas are no longer valid. 

 Under certain conditions the attenuation constant of a particular mode may 

 pass through a maximum as the jacket conductivity is varied. 



Glossary of symbols 



a Inner radius of waveguide 



h = 13 — ia Complex phase constant 



n Angular mode index 



p Denotes p„„, or pnm' according to context 



Pnm in^^ zero of Jn{x) 



Pnm' w*^ zero of Jn{x) 



r, d, z Right-handed cylindrical coordinates 



a Attenuation constant 



/? Phase constant 



/?o = 27r/Xo = wifxoeoY'^ Free-space phase constant 



€o Permittivity of interior medium 



€ Permittivity of exterior medium 



e e/eo 



1347 



e" 



