Topics in Guided Wave Propagation 

 Through Gyromagnetic Media 



Part II — Transverse Magnetization and the 

 Non-Reciprocal Helix 



By H. SUHL and L. R. WALKER 



(Manuscript received March 30, 1954) 



Propagation through a gyromagnetic medium in a direction normal to a 

 uniform magnetizing field is considered. Geometrical arrangements which 

 make this propagation non-reciprocal are described. A few illustrative 

 examples are discussed briefly. The non-reciprocal helix, of importance in 

 traveling wave tube work, is treated at length. 



1. INTRODUCTION 



1.1. General Remarks about Non-Reciprocal Propagation 



Part I of this paper began with a brief discussion of some of the micro- 

 wave properties of two gyromagnetic media; the gas discharge plasma 

 and the ferrite. The remainder of Part I was devoted to the analysis of 

 the mode spectrum in a cylindrical waveguide filled with one of the 

 media and placed in an axial magnetic field. It was demonstrated that 

 the natural modes in such a guide are right- and left-circularly polarized 

 waves which travel with different phase velocities. Accordingly a plane 

 polarized mode, which to some approximation can be regarded as the 

 sum of right and left circular modes, will, in traversing a section of the 

 guide, undergo Faraday rotation, just like a plane wave in the un- 

 bounded medium. It is true that the presence of the guide w^all has a 

 drastic effect on the course of the rotation with magnetizing field, chang- 

 ing it, sometimes beyond recognition, from that prevailing in the un- 

 bounded medium. Nevertheless the principle remains the same ; confine- 

 ment of the wave to a guide merely modifies quantitatively the Faraday 

 effect for plane waves. In optics, wh(>re practically plane waves are 

 almost always employed in this connection, the non-reciprocal nature 

 of this effect is so familiar that it haixlly requires restatement here. 



939 



