Helix Waveguide

Abstract

Helix waveguide, composed of closely wound turns of insulated copper wire covered with a lossy jacket, shows great promise for use as a communication medium. The properties of this type of waveguide have been investigated 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 properties of the jacket. Approximate formulas are given for the propagation constants of the lossy modes. The circular electric mode important for longdistance communication has low loss for zero-pitch helices. The propagation constants of some 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numerically, as functions of the jacket parameters and the guide size, in regions where the approximate formulas are no longer valid.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.