Design and Analysis of a 0.33-THz Sine-Shaped Folded Waveguide Traveling Wave Tube

Folded waveguide (FWG) traveling wave tube (TWT) is an attractive choice for a high-power amplifier. This article proposes a novel slow wave structure (SWS) called sine-shaped FWG (S-FWG), which is derived from conventional FWG. With the feature of transforming the arc-shaped segment of the traditional FWG into the sinusoidal waveguide, the proposed structure could be quickly optimized by modifying the amplitude of the two sine curves, and it has an ability to produce a greater interaction impedance compared to the traditional FWG SWS with the same frequency band, which, under the same operating conditions, is expected to result in a higher output power. Using CST Microwave Studio, the high-frequency properties and beam-wave interaction were simulated. Simulation results indicate that the S-FWG TWT reaches a maximum output power of 16.82 W and a gain of 32.25 dB at 330 GHz with an operating voltage of 19.4 kV, a beam current of 30 mA, and an input power of 10 mW. The S-FWG SWS should therefore be regarded as a promising SWS for the high-power terahertz (THz) traveling wave amplifier.