Estimation of circuit loss in a broadband segment-loaded helical slow-wave structure of a traveling-wave tube

A simple method of estimating the attenuation constant due to conductivity losses in a helix slow-wave structure was developed that uses the inputs like the quality factor and dispersion characteristics obtained from the eigen-mode solutions of 3D HFSS modeling of the structure. The method was benchmarked against two practical structures published in the literature, and applied in demonstrating the computation of circuit loss in a segment-loaded broadband helical slow-wave structure. It was seen that proximity of segment to the helix increases the circuit loss significantly thereby affecting the device efficiency. A study of different parameters that affect the circuit attenuation was also carried out.