Design formulas for helix dispersion shaping

A simple method of calculating effects of various boundaries around the helix on the dispersion relation and the interaction impedance is presented. The analytical technique is based on the use of equivalent circuit parameters derived from rigorous field analyses. The main advantage of this method is that effects of various perturbing objects (dielectrics, shields, etc.) can be calculated independently, regardless of the model of the unperturbed system. Equivalent circuit parameters are obtained for helices with several different forms of perturbing boundaries, including wedge-shaped dielectric rods, conducting boundaries, longitudinally conducting wires and fins, and combinations of these. The method of analysis is versatile so that the dispersion relation for any one particular form of the helix may be calculated from known characteristics of another using only three sets of universal curves.