Equivalent circuit analysis of a system of coupled helical transmission lines in a complex environment

The complex boundary value problem of a system of coupled transmission lines which takes into account the effects of the dielectric and metal shell environment is solved by a simple equivalent circuit analysis. The results are compared with those for a simple system of coupled helices in free space now available in the literature. The effects of the various environmental parameters—like the thickness of the dielectric sleeve for the outer helix, the ratio of the outer helix‐to‐inner helix radii, the ratio of the outer helix‐to‐inner helix contangents of the pitch angle—are studied on the variation of the optimum length with frequency for a system of helical couplers as used in a traveling‐wave tube.