Study On Attenuation Characteristics Of Ridge Waveguide With FDTD

FDTD (Finite Difference Time Domain) has been welcoming in the specialists and scholars'eyes since 1966 when K.S.Yee put forward. FDTD is a numerical computational method based on difference principle and applied to the study of waveguide and resonator cavity system, electromagnetic compatibility, antenna radiation characteristics, interfere with cable transmission lines, electromagnetic scattering,micro-optical components in the optical transmission and diffraction characteristics and so on.As a deformation of rectangular waveguide the ridge waveguide has an important utilization in the practical project. As the ridge waveguide has the character of broader single-mode bandwidth,longer cutoff wavelength of main mode and so forth, it widely applies to all kinds of transition components and resonator cavity and so on. Therefore, the study for the ridge waveguide features is very important. In the early 1940s Cohn studied the features of ridge waveguide and then the ridge waveguide deserved more attention. At present, the study of the ridge waveguide characteristics mainly focus on transfer characteristics and impedance characteristics,rather than attenuation characteristics and power capacities. This phenomenon limited analysis and design of ridge waveguide cell in a degree. To solve this problem, the essay first uses FDTD to study attenuation characteristics and power capacities of ridge waveguide.The composition introduces the principle of FDTD and related techniques which FDTD applies. At the same time, it uses FDTD to model about ridge waveguides and programme in MATLAB circumstances and then calculates attenuation characteristic data and power capacity data in model TE, which are in the light of different structural parameters of rectangle symmetry double ridge waveguides, triangle symmetry double ridge waveguides, trapezoid symmetry double ridge waveguides, inverted trapezoid symmetry double ridge waveguides. Part of data which obtained in this essay is in good agreement with the data which have been existed in authoritative literature of foreign by comparing. All of which had proved the validity and accuracy of the method which had used in this study.The essay uses FDTD combined with MATLAB programmed to calculate attenuation constants and power capacities of ridge waveguides in different structural parameters and offers calculation data charts and change curves. The study result indicates that the attenuation constant and power capacity of ridge waveguide are related to the structural parameter. For example, when ridge distance d/b becomes bigger, the attenuation constant becomes smaller, the power capacity becomes bigger. Therefore, if manufacture technique allows, we can achieve the aim of making power capacity smaller by making ridge distance smaller. There is a conclusion by comparing dates:attenuation constants have this order from big to small:triangle, inverted trapezoid, Rectangular, trapezoid ridge waveguide; and power capacities have this order from small to big:triangle, trapezoid, Rectangular, inverted trapezoid ridge waveguide. In a word, we can see from that although inverted trapezoid ridge waveguide has bigger attenuation constant, it has bigger power capacity. Therefore, inverted trapezoid ridge waveguide can be used as a better microstrip.The data and conclusions in the essay will refer to design the ridge waveguide and will apply to the projects.