Analysis Of Dispersion Characteristics Of Ridge Waveguide And Rectangular Waveguide

Metallic waveguides have been widely applied in communication, radar,electronic countermeasure,and measurement because of large power capacity, simple structure, and easy fabrication. Study on the transmission characteristics of the waveguides is necessary to realize low loss and high output signal transmission. The commonly used waveguides include rectangular and circular ones. Moreover, there is some waveguides with complex boundary, i.e. ridge waveguide. Comparing with the rectangular waveguide, the ridge waveguide has larger cutoff wavelength, wider single-mode bandwidth, and lower equivalent impedance for the dominant mode. Its transmission properties is more difficult because of the boundary. Numerical methods have to be utilized for analysis of ridge waveguide.In this thesis, the finite difference method (FDM) is used to analyze the cutoff wavelength of the rectangular waveguide. The results are in good agreement with those computed by analytical solution. The FDM is applied to analyze the cutoff wavelength of the ridge waveguide. The results by the method agree well with those obtained by the commercial electromagnetic simulation software HFSS. The effect of the different spatial step in the FDM, the size of the waveguide, and the position of the ridge on the cutoff wavelength are also studied. Finally, the 2-D finite difference frequency domain (FDFD) method is used to analyze the rectangular and ridge waveguides filled with dielectric. The relation between propagation constant and the frequency is studied. The results computed by using the FDFD method are in good agreement with those obtained by using the HFSS. The study is meaningful for the waveguide design.