Novel Semi-Ellipse Bending Waveguide Slow Wave Structure for Traveling-Wave Tube

A novel semi-ellipse bending waveguide (SEBWG) slow wave structure (SWS), which evolves from the folded-waveguide slow wave structure (FWG-SWS), is proposed to develop the wide-bandwidth, high power and high efficiency traveling-wave tube (TWT). The major advantages of this novel SWS are flatter dispersion, larger coupling impedance and better transmission characteristics in comparison with the conventional FWG-SWS. With a pencil electron beam of 20.8 kV and 50 mA, the particle-in-cell simulation results show that, the proposed SEBWG-TWT, within the operating frequency band from 150 GHz to 165 GHz, is capable of producing saturated output power greater than 35.5 W. Simultaneously, the maximum power of 51 W, corresponding to the gain of 53.1 dB and the beam-wave interaction efficiency of 4.9%, could be obtained at the frequency point of 159 GHz. Compared with those of FWG-TWT, the output power and beam-wave interaction efficiency of the SEBWG-TWT are considerably improved. At the same time, the SEBWG-TWT achieves length reduction and bandwidth expansion.