Study On Beam-wave Interaction Of Continuous Wave Helix Traveling-wave Tube From 18 GHz To 40 GHz

Helix traveling-wave tube(TWT) is one of the most important microwave electron vacuum devices. Due to its broad bandwidth,high-gain, and high-power, it has been widely used in electronic warfare, radar, satellite communication systems and other fields. The paper mainly focuses on the simulation of high frequency characteristics and beam-wave interaction of the helix TWT. It is based on the program of broad band helix TWT from 18 GHz to 40 GHz. The main work as follows:1. The high frequency characteristics of helix slow-wave structure(SWS) are calculated by using the software HFSS. We focused on the simulation of dispersion characteristic, coupling impedance, and attenuation constant of the helix SWS. It is shown that the helix SWS has a good dispersion characteristic by loading the dielectric support rods and metallic vanes. Furthermore, a negative dispersion characteristic within a certain frequency range is obtained, which is in favor of suppressing the second harmonic. Then we analyzed the high frequency characteristics vary with the structural parameters of the helix SWS, including helix pitch, diameter, width, and thickness. It offers a direction to select the structural parameters of the helix SWS.2. Based on the simulation of high frequency characteristics, we calculated the beam-wave interaction of the helix TWT by using 2.5D large signal code. The demanded high frequency characteristics are determined by the technical specifications of the program. We calculated the saturated output power and electronic efficiency of the slow-wave circuits with uniform pitch. However, it is shown that it can’t satisfy the goal of the program at high frequencies. Therefore, we proposed a helix pitch step method to optimize the slow wave circuit. When the beam voltage and current are 10 kV and 100 mA, respectively, and the circuit length is 150 mm, it is observed that the saturated output power and saturated gain are over 80 W and 35 dB, respectively, and the output power ratio of second harmonic to fundamental wave is below-3 dB. The proposed helix TWT is fully satisfied with our goals. It offers the foundation of the broadband helix TWT from 18 GHz to 40 GHz.