| This thesis proposes a flat-topped sinusoidal double-ridge waveguide,based on which a sheet electron beam BWO high-frequency system and a pencil electron beam BWO high-frequency system operating at 300～350GHz are designed;the high-frequency characteristics of the device and the beam-wave interaction characteristics are analyzed by means of electromagnetic simulation,and the operating performance of the flat-topped sinusoidal double-ridge waveguide BWO is predicted;the transmission characteristics of the sheet electron beam flat-topped sinusoidal double-ridge waveguide BWO highfrequency system are experimentally studied;a new broadband Brewster window is studied and designed to match the BWO.The specific work of this thesis is as follows:（1）The coupling impedance and dispersion characteristics of flat-topped sinusoidal double-ridge waveguide,sinusoidal double-ridge waveguide and conventional sinusoidal waveguide are simulated and compared by using CST simulation software.The results show that the cold bandwidth of the flat-topped sinusoidal double-ridge waveguide is 18%wider than that of the conventional sinusoidal waveguide,and the coupling impedance is 156.6%higher at typical frequency point of 340 GHz;Finally,the relationship between the dimensional parameters of the flat-topped sinusoidal double-ridge waveguide and the slow-wave characteristics is studied and analyzed to provide theoretical guidance for subsequent work.（2）Using flat-topped sinusoidal double-ridge waveguide as a slow-wave structure,a design of sheet beam BWO that can operate in 300～350GHz is proposed,and its highfrequency system is designed.Using CST particle studio simulation to calculate the working performance of the sheet beam flat-topped sinusoidal double-ridge waveguide BWO,the results show it can obtain an output power of more than 4.25W in the frequency band of 301.5GHz-351.3GHz under the uniform focusing magnetic field of 0.8Tesla,sheet beam current of 30mA,and tuning voltage of 11kV-19kV,and the highest output power can reach 5.79w,with an average interaction efficiency of 1.19%.（3）A design of a pencil beam flat-topped sinusoidal double-ridge waveguide BWO that can work in 300～350GHz is proposed,and its high frequency system is designed.With an uniform focusing magnetic field of 0.6 Tesla,an pencil beam current of 25mA and a tuning voltage of 11kV-18kV,this BWO can obtain an output power of more than 2.78W in the frequency band of 304.6GHz-351.2GHz,with a maximum output power of 3.33W and an average efficiency of 0.87%.（4）The high-frequency system of sheet beam flat-topped sinusoidal double-ridge waveguide BWO was processed,and experimental studies of its transmission characteristics were carried out,and the measurement results showed:in the frequency band from 260GHz to 355GHz,except for the reflection parameter S11 near 274GHz,which is around-13dB,S11 was less than-15dB in the rest of the frequency band,which indicates the HF system has a very low reflection;in the whole frequency band from 260GHz to 350GHz,the transmission parameter S21 is around-5dB.However,the machining accuracy is poor,and the excessive tool marks and edge burrs increase the transmission loss of the HF system compared to the simulation results.（5）A novel ultra-wideband Brewster window for use as an output coupling system has been investigated,The simulation results show that the S11 parameter is mostly below-20dB in the frequency band of 300GHz-350GHz,and the overall trend of the S21 parameter is around-1dB,indicating that it has very good transmission characteristics and is suitable for use as a window for ultra-wideband submillimeter wave BWO. |
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