A Novel Gap-Groove Folded-Waveguide Slow-Wave Structure for G-Band Traveling-Wave Tube

In this paper, a novel gap-groove folded-waveguide slow-wave structure (SWS) for high-efficiency G-band traveling-wave tube (TWT) is presented. In this novel tube, a sheet electron beam passes through the small gap between a bed of nails and a folded groove realized in a metallic plate. The bed of nails and the metallic plate form a high impedance structure-perfect electric conductor parallel plate waveguide, which prevents the fields from leaking transverse to the propagation direction. The phase velocity of the proposed SWS has been analytically calculated and the results show good agreement with those obtained using Eigenmode solver of computer simulation technology (CST). Meanwhile, the simulation results indicate that the interaction impedance of the proposed SWS is considerably higher than the conventional folded-waveguide SWS. Furthermore, employing a proper phase velocity taper in the end section of circuit leads to increasing the efficiency of the proposed TWT. According to Particle-in-cell simulations performed by the CST Particle Studio, the designed TWT can generate a peak power of 225 W at 220 GHz, corresponding to the maximum gain and efficiency of 42.7 dB and 14.9%, respectively.