The Research Of Terahertz High Harmonic Traveling Wave Tube

In the field of electromagnetic field,the terahertz which known as submillimeter waves and ultra microwaves,are a kind of electromagnetic waves between millimeter waves and infrared rays.Terahertz technology is widely used in military industry? high rate communication?aerospace?explosive detection and other potential areas.Microwave vacuum devices are considered as the most promising way to realize THz source in society.In this paper,we combine the principle of free electron laser with the principle of wave-beam interaction of traveling wave tube,and get a new type of terahertz vacuum TWT device--two beam THz frequency harmonic TWT,The advantage of the device is to obtain a stable and high power terahertz wave signal from a low cost millimeter source.The millimeter wave modulated the electronic beam,then the electronic beam will contain all kind of high harmonic signals,we can select a certain high harmonics to enlarge and restrain the remaining harmonic signals.The main research contents of this paper are as follows:1.firstly,the high frequency characteristic and loss characteristic of slow wave structure are studied in the first part,we analyzed the dispersion characteristic,coupling impedance and loss of slow wave structure,the basic theory of folded waveguide is introduced,the design of each component of traveling wave tube is analyzed,and get the certain structural parameters of TWT,according to these structural parameters,the interaction of beam-wave interaction is studied in feasibility analysis.2.The design and simulation of the electronic optics system of two beam THz frequency harmonic TWT,the type of the electron gun is Pierce electronic gun without grid,the focusing system is the periodic permanent magnet structure(PPM),the electron gun working voltage is 19 kV,the working current is 15 mA,the radius of the electron beam channel is 0.1mm.The cathode surface of electron gun is curved surface.We get a excellent electronic optics system through our a series of optimization,and it can be applied to the two beam THz frequency harmonic TWT in this paper.3.In this chapter,We analyze the input and output structure research,designed a W band of the input window structure,THz output window,and their transitional waveguide structure,the voltage standing wave ratio of the input window is less than 1.4,and the voltage standing wave ratio of the THz wave output window is less than 1.3,the voltage standing wave ratio of transition waveguide of the input window is less than 1.25,the voltage standing wave ratio of transition waveguide of the output window is less than 1.05,the dates meet our design requirements.4.We introduce the basic theory of beam-wave interaction of TWT,and analyses and studies the interaction of beam-wave in two beam THz frequency harmonic TWT,then optimizes the process.We can get 50mW-1.62 W the output signal which is the fourth times high harmonics(343GHz-348 GHz terahertz signal)by inputting 100 mW the W-band Signal of the 84.5GHz-87.5GHz.The output signal spectrum is pure without other clutter signal interference,and the frequency of the diverted wave tube can be adjustable,which proves that two beam THz frequency harmonic TWT can amplify the signal and obtain the better high harmonics signal,and help using in some areas.