G-band Continuous Wave Broadband Traveling Wave Tube Design

G-band traveling wave tube as a broadband high-power terahertz signal source in communications,imaging,radar and other fields has a very wide range of application prospects.With the increasing frequency band of traveling wave tube research,the size of traveling wave tube high-frequency structure is also decreasing,and the loss is also increasing accordingly.Therefore,wide bandwidth,high power and practical processing are the key issues in the design phase of the traveling wave tube high frequency structure.The conventional sine waveguide slow-wave structure has the advantages of wide bandwidth and low loss,but in the actual processing process,it is difficult to process the ideal structure because the size of the slow-wave structure gradually decreases with the increase of operating frequency.This thesis firstly introduces the model of quasi sine waveguide,slow wave characteristics,processing method and comparison with other structures based on conventional sine waveguide.Secondly,we design a 220 GHz single-section quasi sine waveguide slow-wave structure and a 17 k V dual-section quasi sine waveguide slow-wave structure based on the conventional sine waveguide.Then the high frequency structure of the 263 GHz quasi sine waveguide traveling wave tube is designed.The specific work is as follows.1.Based on the conventional sine waveguide,the model of the quasi sine waveguide,the slow wave characteristics,the processing method and the comparison with other structures are introduced.It is verified that the improved sinusoidal waveguide has excellent slow wave characteristics and transmission characteristics,and has more advantages in processing.2.220 GHz single-section quasi sine waveguide slow wave structure is designed,with total tube length of about 39 mm,actual operating voltage of 17.2 k V,operating voltage of 35 m A,output power of more than 10 W and gain of more than 30 d B in the operating band of 216 GHz-225 GHz.3.220 GHz dual-band quasi sine waveguide slow wave structure is designed,with total tube length about 44 mm,operating voltage 17.2 k V,operating current 35 m A,and phase speed hopping technology is adopted at the end 15 periods.In the operating band of 214 GHz-226 GHz,the output power is more than 14 W and the gain is more than 28 d B.the results show that the output power and electronic efficiency of the two-band slow wave structure with phase speed tripping have been improved.The 263 GHz quasi sine waveguide traveling wave tube high frequency structure is designed with the total tube length of about 41.4 mm.including the input-output coupling structure with sapphire box window,the output power is more than 10 W and the gain is more than 30 d B in the operating band of 247 GHz-273 GHz at the operating voltage of 17.1 k V and the operating current of 35 m A.