Polarization properties of the axial mode helix antenna

The helix is considered as a surface wave antenna. A network model of the infinite structure provides a simple vehicle to view the fields behavior. The far-field polarization properties are examined in detail, and it is shown how they depend on the surface wave structure and the open and feed end configurations. By suitably arranging the antenna ends, perfect endfire polarization purity can be produced independent of antenna length (i.e., number of turns). Inclusion of a dielectric core decreases the cross polarized radiation in off-axis directions. Theoretical and experimental patterns illustrate these results.