Research On Ka-Band Mode Converter And Waveguide Bend

Mode converter and waveguide bend are essential transmission devices in the process of high power microwave transmission.Mode converter and waveguide bend can effectively transmit the energy of microwave source,the former can effectively change the transmission mode,the latter can adjust the transmission direction.Therefore,both of them have wide application value and high research value.The main work and contributions of this paper are as follows.1.This paper summarizes the development and application of high power microwave,and introduces the development and research status of gyrotron.After comparing the merits and demerits of several T₁₀^□-TE₀₁^○mode converters and circular waveguide bend,T₁₀^□-TE₀₁^○cross mode converters and miter bend are selected for research and design.2.The transmission characteristics of the rectangular waveguide and circular waveguide are briefly introduced.Then the coupling wave equation of tapered waveguide structure is derived in detail according to the coupling wave theory,and the coupling coefficient of each mode is summed up,which provides theoretical guidance and basis for the design of waveguide mode converter.3.According to the needs of theory and practice,the key points in the design of TE₁₀-TE₀₁ cross mode converter are put forward,and the method of linear transition is used to realize the mode conversion.The model is modeled and simulated in the electromagnetic simulation software HFSS,and finally a TE₁₀^□-TE₀₁^○mode converter with high efficiency,wide band,compact structure and working in Ka band is obtained.At the same time,the error of the mode converter is analyzed.Although there is deviation in some frequency points,the slight change of the key size has little effect on the conversion efficiency of the mode converter,which provides a certain reference for the actual processing.4.In this paper,the diffraction loss of the miter bend is analyzed,and the equivalent structure of the miter bend is obtained by using the gap theory.Then,according to the principle of diffraction minimization when the mixed mode is transmitted in the equivalent structure,the Runge-Kutta algorithm is used to design the mode converter.Finally,the 90°miter bend of TE₀₁ mode with center frequency of32GHz,transmission efficiency of 99.52%and power capacity of 0.988GW is obtained.The transmission efficiency of the elbow is over 95%in the frequency range of 31.2GHz-33.5 GHz.5.Based on quasi-optical theory,the Gaussian beam is analyzed briefly and the Gaussian mode is expanded into TE_0nn mixed mode.After designing the mode converter and phase-shifting section,the simulation results in HFSS show that the transmission efficiency of TE₀₁ mode 90°miter bend is 99.28%and the power capacity is about 601MW at 27.94 GHz.6.Three kinds of 160°TE₀₁ mode circular waveguide bend with different structures are designed on the basis of 90°miter bend with center frequency of27.94ghz.After modeling and Simulation in HFSS,the transmission efficiency at the center frequency point is 93.71%,94.32%,95.22%,and the power capacity is 854 MW,619 MW and 501 MW,respectively.