Research On High-efficiency Bent Circular Waveguide Mode Converter

Nowadays,the development of microwave and electromagnetic wave technology has made it impossible for countries to ignore their research.Among them,high-power microwave technology is the focus of each country's research.This is because high-power microwaves are used in the national defense military or in universities and research.The role of the institute in scientific research is huge and difficult to replace.High-power microwave sources,high-power microwave transmission systems,microwave transmitters,and other discrete components together form a high-power microwave system.In the entire microwave system,the high-power microwave transmission system is a very important part.Effective transmission of microwaves affects the performance of the entire high-power microwave system.In common microwave devices,various mode converters and various types of mode transitions are part of the microwave transmission system.Whether these devices can work efficiently determines the efficiency of the entire transmission system.The mode converter is the main object of the design and research of this paper.It is mainly through some global optimization algorithms and new design methods to design a mode converter with high efficiency and a small and compact structure.And through the analysis of coupled wave theory,a MATLAB program is written to numerically solve the deduced coupled wave equation,and finally the obtained structure curve is modeled and simulated.This design method,which first calculates the device structure through a numerical program,and then performs CST simulation calculation,can save a lot of time compared to directly using simulation software for optimization.When solving the coupling structure,this paper also uses the optimization algorithm to optimize the design of the control parameters of the structure curve,and a more reasonable structure can be obtained.The main research content of this paper:1.Study the principle of mode coupling in circular waveguides,derive the mathematical expressions of coupled wave equations and coupling coefficients,study the theories and methods commonly used in numerical solutions,and write MATLAB numerical calculation programs for solving coupled wave equations and coupling coefficients.2.Study the design method of the traditional TE₀₁-TE₁₁mode converter,and give an initial coupling structure combining sine and cosine,combining the coupling wave equation solving program and the coupling coefficient calculation program to design a center frequency of 32GHz,waveguide TE₀₁-TE₁₁mode converter with a radius of14mm.Then study the optimization design algorithm,including particle swarm algorithm,genetic algorithm and simulated annealing algorithm,write an optimization program based on MATLAB implementation,and use the optimization program to design and optimize the control parameters in the coupling structure given at the beginning,and finally obtain the numerical calculation mode conversion efficiency and optimized The coupling structure curve is then modeled and simulated in CST to obtain the frequency sweep curve of the conversion efficiency,and the absolute bandwidth and relative bandwidth can be obtained.Finally,the optimization results of the three algorithms are compared,including the length,the conversion efficiency of the numerical calculation,the conversion efficiency of the simulation calculation,and the maximum power contained in the device.3.Study the design of the coaxial mode converter,using two design methods,namely iterative design method and NURBS curve method.Research the iterative method,determine the gradient direction and the value of the iterative step length in the design process,and write the solution program,and then add the structure control function based on the iterative method,which is the port parallel function and the coaxial function,write a program to design a high-efficiency converter from TE01 mode to TE11 mode,and let its working frequency be about 32GHz,and the waveguide radius is 14mm.NURBS curve is a non-analytic curve commonly used in engineering.This article clarifies the basic theory and the selection of control points and node vectors by studying the NURBS curve.It also gives a method to approximate the curvature of the curve from discrete points.A MATLAB program was written to design a coaxial TE₀₁-TE₁₁mode converter with a center frequency of 10GHz and a waveguide radius of25mm.The CST modeling and simulation of the mode converters designed by the above two methods are carried out to verify the correctness of the program design.