| 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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