Thermo-mechanical analysis on reflection characteristics of deformed coupling system of a helix traveling wave tube

This paper proposes a fast ANSYS Multiphysics-based system coupling approach to study the impact of structural deformation on the reflection coefficient (S11) of the helix travelling wave tube (TWT) output coupling system at varying output powers. The system, comprising a coaxial stepped impedance transformer, a coaxial-to-rectangular waveguide with a door-knob transition, and a double-mitered bend waveguide, is analysed under 200 W and 250 W RF power in the X-band. The analysis shows that S11 improves at lower frequencies (−17.43 dB to −17.58 dB) and deteriorates at higher frequencies (−10.62 dB to −10.53 dB) due to structural deformation. Thermal simulation results were validated experimentally using infrared thermographic imaging.