A heuristic analysis for an inhomogeneously loaded tape helix used in a practical travelling wave tube

Abstract

The analysis of an inhomogeneously loaded helix in the tape model, reported elsewhere, considering the effect of space harmonics as well as the different radial propagation constants over the different structure regions, is quite tedious and rigorous. So, to avoid the rigorous analysis here, a heuristic analysis has been developed by combining the results of the tape model analysis of a helix in free space with those of the sheath helix model analysis of a loaded helix. The results presented here in terms of dispersion characteristics have been compared with those results obtained from a rigorous approach (both for homogeneously and inhomogeneously loaded structures) in the tape helix model. However, the results obtained from this approach agree closely with those of the rigorous approach for a practical situation in which the discrete supports are smoothed out into a single continuous region. The approach is valid for an inhomogeneously loaded helix for optimum conditions of structure parameters, namely, helix pitch angle, helix to barrel gap, support material and inhomogeneity. Moreover, the results predicted by this heuristic approach have also been validated with those experimental results published in the literature and are found to be in good agreement.