Investigation and Experiment of a Novel Chamfered V-Shaped Microstrip Slow-Wave Structure for W-Band Traveling-Wave Tube

A novel chamfered V-shaped microstrip meander line (MML) slow-wave structure (SWS) based on the V-shaped MML SWS for W-band traveling-wave tube (TWT) is proposed to decrease the transmission loss and thus to improve the output power and beam-wave interaction efficiency. The high-frequency characteristics, transmission characteristics, and the beam-wave interaction processes of the novel structure are investigated by simulations. The simulation results show that the S₂₁ parameters of the chamfered V-shaped MML SWS are improved by 4.3 dB for 100 periods compared with that of the traditional V-shaped MML SWS at 95 GHz. Besides, the particle-in-cell simulations indicate that the output power of the TWT with the novel structure is 30% higher than the V-shaped MML SWS in W-band. Finally, two types of SWSs with 100 periods are fabricated, assembled, and experimentally tested. According to the experimental test results, while the S₁₁ parameters are below − 20 dB, the “cold” S₂₁ parameters are − 17.04 dB vs − 20.74 dB at 95 GHz, which shows potential advantages of the proposed novel SWS in millimeter wave and even terahertz spectrum.