Rectangular Gate Slow-wave Systems And Input-output Structure

TWT is an apparatus that can amplify the energy of microwave. And its slow-wave system is the part where the electrons interact with the microwave and exchange energy with the microwave. It relates to the bandwidth, efficiency, etc of TWT. It decides the capability of TWT directly. The input and output structure of TWT is the input and output ports of the signal amplified. The matching impedance and wastage relate to the TWT can or can not work up to snuff. They are the problems which need be solved when we design the input and output apparatus.The characteristics of slow-wave structure with gratings are that the structure is compact, it can be used in the situation of short wavelength and small size; the precision of machining is high, it can be used in millimeter wave and submillimeter wave TWT. It uses the sheet electron beam, so its power is high and the thermal capacity is big. This paper uses grating as slow-wave system. It starts to analysis from arbitrary grooves grating structure, and obtains the distributing of field, dispersive function, and coupling impedance. From those, we also obtain the distributing of field, dispersive function, and coupling impedance of rectangle grating structure. We analysis the dispersions of the single grating structure and double gratings structure by CST, and obtain the influence of structural parameters to the dispersion, and get the size of ka-band single grating or double gratings slow-wave structure.Besides pressurizes, the microwave window of the input and output apparatus(including the input window and the output window)also transmits microwave energy. The quality of the microwave window impacts on the electrical parameter and the life-span of TWT. Its basic requirements are: having enough of working frequency bandwidth, power capacity is big, the inserting wastage is small, the capability is good. This paper designs a microwave window which has a 110GHz center frequency, and a more than 9GHz bandwidth. It is connected to the input and output structure of deep groove single grating slow-wave system, and we obtain a good result.