Theoretical Modeling And Numerical Analysis For Electromagnetic Transmission And Radiation Of Mutimode Waveguide

Mode is an important characteristic of electromagnetic wave propagate in the waveguide. Multimode waveguide is a waveguide used to propagate power in more than one mode. In field of radar and high power microwave(HPM), multimode waveguide has a wide range of applications, therefore accurate electromagnetic modeling and efficient numerical analysis for multimode waveguide is the basis of the relevant areas of engineering applications. Integral Equation(IE) method is used for electromagnetic modelling of multimode waveguide, Mode Matching(MM) mehtod is used to describe field distribution on the waveguide excitation port. Dielectric structure in multimode waveguide has a great impact on field distribution in the waveguide, so it’s important modelling metal-dielectric composite structure accurately. The surface integral equation method is used in this thesis as a solution of dielectric structure. Applications of multimode waveguide in HPM, such as Denisov launcher and beam waveguide antenna are simulated in this thesis, and the physical interpretation of the results is given.Firstly, integral equation method is introduced as the the theoretical basis. The IE-MM hybrid method is introduced to establish waveguide transmission-radiation model. Number of modes should be accounted in IE-MM method is interpreted through numerical example. For waveguide with metal wall of finite thickness, integral equation is established both inside and outside of the waveguide, the method of moment is used to solve the formulation, numerical results show that proposed method is right.Secondly, the EFIE-PMCHW-MM hybrid method is proposed in this thesis to solve the problem of multimode waveguide with composite metallic-material structure. The Electric Field Integral Equation is established on the surface of metal wall, the PMCHW equation is established on the surface of dielectric structure, the mode matching equation is established on the waveguide port. In EFIE-PMCHW-MM method, the unknowns exist only on the target surface, so the hybrid method is more efficient than other full wave numerical method.Then a strategy to combine MLMFA with IE-MM is proposed in the thesis and the computational complexity and storage complexity is also analyzed. Numerical results show that this combination strategy can improve the computational efficiency.Finally, some multimode waveguides used in HPM are simulated, such as exponential horn antenna, denisov waveguide launcher and beam waveguide antenna. The physical interpretation of the simulation results is given.