Phase velocity dispersion of a generalized metal-segment-loaded helix as used in broad-band traveling-wave tubes

An analytical model for predicting phase velocity dispersion of tape helix circuits loaded with solid-type or vane-type metal segments is described. An accurate design formula for dispersion is derived from the concept of the developed tape helix, taking account of the thickness effects of the tape and the edge effects of the metal segments. Comparisons with measurements of four solid-type and one vane-type helices show about ±1% accuracy, which is seen to be sufficient for practical applications, The model can also be used to calculate a wide variety of asymmetry effects in loading elements around a tape helix