Study On Transmission Characteristics Of Special Ridge Waveguide Based On FDTD Method

Waveguide is the important component of microwave communicationengineering, compared with rectangular waveguide, the single-mode bandwidth ofridge waveguide is wider and the main mode cut-off wavelength is longer. The ridgewaveguide has been widely used in microwave and millimeter wave device since itwas invented. Solving the electromagnetic field problem of the ridge waveguide is thetheoretical basis of waveguide designing, the method to solve the electromagneticfield problem are as follow: the moment method (MoM), finite difference method(FEM), boundary element method (BEM), finite element method (FDM),finite-difference time-domain method (FDTD) and so on. The FDTD method takesthe electromagnetic field problem as an initial value problem, which directly obtainsthe time-domain characteristics of electromagnetic field. This directly provides richtime-domain message of electromagnetic field. Nowadays, the FDTD method hasbeen widely used in the fields of the electromagnetic radiation, scattering, antenna,optoelectronics, microwave and millimeter wave technology. In this paper, FDTDmethod is applied to analyze two novel kinds of complicated ridge waveguides, andthe cut-off characteristic, the bandwidth characteristics and the dispersioncharacteristics of the waveguides have been studied.Firstly, the thesis reviews the basic principle of the FDTD method, the FDTDformulas of three-dimensional electromagnetic field problem and the differenceequations of FDTD method for two-dimensional and three-dimensional problemassociated with anisotropic medium are given. The requirement for the time intervaland courant condition for stability of FDTD, method handing of different boundaryand optimization design excitation sources in making programs, are discussed.Secondly, in order to verify the FDTD method, the transmission properties ofSHAN ZI ridge waveguide are calculated and compared with the results reported inthe literature. The cut-off characteristic and the dispersion characteristics of the emptySHAN ZI ridge waveguide have been given. The transmission properties of the SHAN ZI ridge waveguide partly filled with different medium have also been given.The relationship between the size of the ridge waveguide and the transmissionproperties is discussed.Finally, an I-ridge waveguide is proposed. The cut-off wavelength and thedispersion characteristics of the empty I-ridge waveguide have been obtained by theFDTD method. The transmission properties of I-ridge waveguide partly filled withisotropic medium and anisotropic medium is discussed.