Design and Analysis of Width-Modulated Two-Section Sine Waveguide for G-Band Traveling-Wave Tube

A novel width-modulated sine waveguide traveling-wave tube (SWGTWT) is proposed for G-band operation. The broadband single-section and two-section SWGTWT are analyzed, which has the potential to address various technological challenges in the THz regime, such as fabrication difficulty, reflection, and attenuation of RF power. The two-section design has separate RF structures for input and output sections of the TWT, which helps to eliminate undesired reflection during high-power operation. The width modulation is employed to enhance the interaction impedance and also to realize the flat dispersion characteristic of the slow wave structure (SWS). The fabrication feasibility of the structure is demonstrated by fabricating the scaled structure at the Ku-band. A 20.4-kV, 50-mA cylindrical beam is employed in the particle-in-cell (PIC) simulation. The single-section structure offers a maximum power of 53 W with a 5.19% efficiency at 210 GHz. The peak power and a 3-dB bandwidth for the two-section structure are estimated to be 38.9 W and 32.5 GHz, respectively. The structure produces greater than 10 W of output power over a 46-GHz frequency band covering the range of 200–246 GHz.