| High power gyrotrons have a wide range of applications in the millimeter-wave radar and communications and other fields because of its high power and wide bandwidth advantages,the researchers attach great importance to its development at home and abroad.Waveguide mode conversion devices involved in the output system of cyclotron wave tubes,such as waveguide bends have become hot spots among the researchers at home and abroad.The waveguide bend is one of the important devices in the microwave transmission system.In the case of high-power transmission,the operating mode in the circular waveguide bend will be converted to the parasitic modes,and this coupling is difficult to eliminate by the way of curvature structure,this will greatly affect the bend work performance.Compared with the overmoded circular waveguide,the coupling between the modes in the curved rectangular waveguide is easier to control,and the use of the characteristics of the rectangular waveguide to realize the wide frequency band and high efficiency of the waveguide is the focus of this paper technical problem.The main work and contribution of this paper are listed as follows:1?The coupling coefficients between the modes in the rectangular curved waveguide are summarized.2?On the basis of the theoretical derivation,a numerical solution program of the rectangular waveguide coupled wave equation is written.And the simulation model is established in the simulation software HFSS.The simulation results are compared with the numerical results,and the correctness of the numerical calculation program is verified.However,in the analysis speed,the speed of the numerical calculation program is about 200 Times,which greatly reduces the time required for the analysis,for the follow-up large size bend optimization calculation provides the necessary tools.3?Using the numerical calculation tool and simulation software,the TE01 bend with rectangular structure,diameter of 50 mm and working in Ku-band is optimized.The results are as follows: the transmission efficiency of more than 96% of the bandwidth can reach 13.9%,the maximum transmission efficiency of 99.97%.4?Using a numerical calculation tool and simulation software,a polarized controllable TE11 bend was analyzed and optimized.The bend was operated in Ku-band with a diameter of 32 mm.The proposed structure can ensure that the TE11 mode can be realized while the TE11 mode line can be realized,and the TE11 mode polarization can be realized.In order to verify the feasibility of the program,the second case of the bend was processed test,S-parameter test results show that: 13GHz-15 GHz frequency range,TE11 bend transmission efficiency is higher than 97%;space radiation Field test shows that the linearly polarized TE11 mode can maintain the output with constant polarization direction after passing the bend.The power capacity test results show that when the frequency is 13 GHz ~ 15 GHz,the peak power is 120 k W and the average power is 10.4k W,the bend did not occur breakdown phenomenon.5?In view of the successful application of rectangular curved waveguides in bends,this chapter also attempts to apply rectangular curved waveguides to the design of the TE01-TE11 serpentine bending mode converter,hoping to explore a high performance mode converter Design.Combining with numerical calculation tools and simulation software,an optimized design of TE01-TE11 serpentine bending mode converter with Ka band and aperture of 23 mm is made.The results show that the maximum conversion efficiency is 98.5% and the relative bandwidth is 11.5%.6?The paper also calculates and analyzes the rectangular waveguide TE20-TE10 mode converter with a diameter of 44 mm * 30 mm and operates in the Ka band.It is found that the rectangular mode converter can realize high efficiency and wide band mode in one period length. |
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