Abstract:The slow wave characteristics of truncated sine waveguide are analyzed by the simulation method. The two-section high frequency electromagnetic system based on truncated sine waveguide is proposed, which can be used for the W-band Traveling Wave Tube (TWT). Meanwhile, the input/output coupler and attenuator are designed for the high frequency system. We obtain the beam-wave interaction results in the high frequency electromagnetic system by the Particle-in-cell（PIC）simulation method. The PIC simulation results indicate that the TWT can produce the output power over 200W and gain over 30dB in the frequency range of 92-101GHz.