Study On The Cut - Off Characteristics Of Left - Handed Medium - Filled Waveguide Based On FDTD Method

Left-handed materials is a new type of artificial materials，compared with theregular material, left-handed material has some unusual electromagnetic properties.In recently years, it has been one of the hot spot fields of electromagnetic field andmicrowave technology study. At present, reports about the waveguide filled withleft-handed medium are relatively scarce. In this paper, based on electromagneticfundamental theory, the FDTD formula of the metal waveguide filled with theuniaxial anisotropic left-handed medium has been deduced. By the FDTD method,the cut-off characteristic and absolute bandwidth of left-handed medium partiallyfilled in rectangular waveguide, L-shaped waveguide and double-ridge waveguide,have been studied.The thesis reviews the basic concept of the basic principle of the FDTD method,gives FDTD formulas of2D(two-dimensional) and3D(three-dimensional)electromagnetic field problem, and discusses the numerical stability conditions ofFDTD method, boundary processing method, the excitation source problems ofFDTD method, and absorbing boundary conditions. The FDTD formula of metalwaveguide, filled with uniaxial anisotropic left-handed medium related with the coldplasma model and Drude model, has been derived. Using the derived formula andthe program, the cut-off characteristic of the left-handed medium (isotropicleft-handed medium and uniaxial anisotropic left-handed medium) partially filled inrectangular waveguide has been analyzed, the absolute bandwidth of the left-handedmedium partially filled in L-shaped waveguide and cut-off characteristic of theleft-handed medium partially filled in double-ridge waveguide bas been obtained.The calculated results show the following conclusions:(1) the rectangularwaveguide filled with the left-handed medium, the TE mode cut-off frequencyincreases with the increasing of filling thickness. When the thickness of the mediumis determined, the TE mode cut-off frequency increases with the relativepermeability filled medium.(2) The L-shaped waveguide partially filled with left-handed medium, the absolute bandwidth increases firstly, then decreases withh/a (deformation of the geometric parameters) and relative permeability of themedium.(3) The double-ridge waveguide partially filled with left-handed medium,the TE mode cut-off frequency decreases with the increasing of filling thickness andthe right-handed medium filling is contrary.