Study on Effects of Different Metallic Vane-Loaded Helix Slow-Wave Structures in Traveling-Wave Tubes

The effects of different metallic vane-loaded helix slow-wave structures of a traveling-wave tube are proposed based on the analysis of the Fourier expansions of the exterior region with metallic vanes. The influences of the metallic vanes dimensions on the phase velocity and interaction impedance are considered in detail. The computed data is compared with the reference data in the 0−16 GHz frequency range with a good consistency. The analytical results reveal that the method of using Fourier expansions can contribute effectively to the reducing of the error between the theoretical and experimented data (around 1.2%). By analyzing the computed results, the performances of the helix slow-wave structure, with T-shaped metallic vanes are superior to the sector-shaped with the same designed parameters. Adjustments can be made to the outer radius of T-shaped metallic vanes which then control the dispersion relation showing either negative or positive, and it is similar to sector-shaped vanes by adjusting its inner radius. And with increasing the distance between the helix and metallic vanes, the dispersion characteristics and interaction impedance of the helix slow-wave structure with T-shaped/sector-shaped metallic vane are all improved.