Simplified tape model of arbitrarily-loaded helical slow-wave structures of a travelling-wave tube

A simplified tape model has been proposed to obtain the dispersion relation for helical slow-wave structures loaded in a complex manner. It combines the tape model results of field analysis for a helix in free space with the sheath model results of equivalent circuit analysis of the structure with complex loading, which are available in the literature. The dispersion relation obtained by the proposed model, for a helix supported by arbitrarily shaped dielectric support bars in a vane-metal envelope, is found to be identical with that obtained using the tape model of Sensiper (1951) for a helix in free space extended to the case of a loaded helix. The structure considered is quite general. Any specific structure of interest may be interpreted as a special case of this structure. The theoretical results are compared with experimental results reported in the literature