The Design Of Miniaturized Helix TWT Within The Range Of 6GHz To 18GHz

Helix traveling-wave tube(TWT) is one of the most common microwave electron vacuum devices. It has been used widely in many fields such as radar, electronic,communication and so on because it has a lot of advantages-broad bandwidth, high gain and high power. For the need of modern military and communication, helix traveling-wave tube becomes smaller and smaller. 6-18 GHz miniaturized helix traveling-wave tube is designed in this paper, and slow-wave structure, high-frequency characteristics, beam-wave interaction and collector of the helix traveling-wave tube are studied. Finally, two tubes are successfully made and tested. The main content is as follows:1. The development process, basic structure and basic theory of TWT are introduced detail, which play a significant role in guiding the next design of the TWT.2. Based on manufacture difficulty and project index, slow-wave structure is designed, which is composed of T-shaped support rod and fan-shaped ridge.3. In the range of 6-18 GHz, using electromagnetic simulation software,high-frequency characteristics of the designed slow-wave structure, which include dispersion characteristics, coupling impedance and attenuation constant, are optimized.Also, high-frequency characteristics are analyzed with change of helix pitch, angle of the fan-shaped ridge, depth of the fan-shaped ridge and width of the T-shaped support rod.4. For the need of the project, two programs are designed. The first program uses negative pitch and then positive pitch transition, uniform magnetic, and ladder attenuation; the second uses negative pitch, then positive pitch and last positive pitch transition, different magnetic and ladder attenuation. Finally, using Ukraine simulation software, the beam-wave interaction of the two program are calculated, and result is as follows: the gain of program 1 is superior to program 2, while the harmonic of program 2 is superior to program 1; the output power of program 1 in middle frequency is higher than program 1, but in the low and high frequency, program 2 is high than program 1.5. Obtaining four depressed collector, the collector of the TWT is made. Using electromagnetic simulation software, collector efficiency is calculated. And the resultshows that the efficiency of the collector in the band is more than 60%.6. Two tubes are successfully made and tested, the result which has been studied is as follows: The gain of two tubes reaches 28 dB which is needed for the project except6 GHz, the output power is higher than 200 W, and total efficiency is more than 35%except 6GHz. Finally, after careful analysis for the the experimental result and simulation result, several important conclusion can be reached: Gain of simulation result and experimental results remain almost the same trend; Input power of the simulation result is similar to the experimental results; Because of local change of output power is relatively large, but generally speaking, the trend is experimental results;General speaking, in some aspects, the experiment verify rationality of simulation results.