|Abstract:In order to develop high frequency, broad bandwidth and low voltage traveling wave tube (TWT), the folded rectangular coaxial waveguide slow wave structure (FRCW-SWS) is proposed in this paper. Operating at overmode condition, the proposed FRCW-SWS has relatively high operating frequency and acceptable transmission characteristics. A double ridge-loaded waveguide-to-coaxial-waveguide converter is designed and applied as the input/output coupler to incorporate the broadband characteristics of the FRCW-SWS. The hot performance of this overmoded FRCW-TWT at W-band is investigated using particle-in-cell (PIC) simulation. The simulation results indicate that the output power can be over 13.7W in the frequency range of 76-110GHz, when the length of the SWS, the beam voltage and beam current are 32mm, 3230V and 150mA, respectively. The maximal output power is about 27.4W at the frequency of 108GHz, corresponding to the RF efficiency of 5.65%.