Design and Analysis of Truncated Velocity Tapered Sine-Waveguide Structure for Traveling-Wave Tube in THz Band

A truncated sine-waveguide traveling-wave tube (SWGTWT) is studied to obtain wideband amplification at 600 GHz. The cold test parameters are obtained and finalized through simulation to achieve minimum dispersion coupled with a high interaction impedance. The interaction impedance at various points of the beam tunnel cross section area is evaluated to choose the right shape of the electron beam for the TWT. The effect of velocity tapering on the SWG structure is studied. Particle-in-cell (PIC) simulation is carried out using cylindrical as well as sheet beams. The velocity-tapered structure exhibits higher power and efficiency. The maximum output power and 3-dB bandwidth are estimated to be 7 W and 40 GHz, respectively. The corresponding gain and electronic efficiency of the truncated SWGTWT are 25.4 dB, and 1.88%, respectively.