Heavily-loaded wideband helix traveling wave tube

The negative dispersion in a wideband helix TWT is operative for ensuring a successful operation with lower second harmonic at the lowest frequency and higher power at the highest frequency. In the previous work, we studied a wideband TWT experimentally with a relatively simple SWS which uses rectangular BeO rods without the metal vanes. The angular thickness of the rectangular supports is made larger than their radial thickness, which makes this structure somewhat ´heavily loaded´. In this study, unequal rectangular ceramic rods were employed to enhance the second harmonic level at the lower frequencies and efficiency at the higher frequencies. The dispersion and the interaction impedance of the structure were predicted by a 3-D HFSS code. The hot simulations carried out using a 1-D nonlinear code.