| Summary: | 碩士 === 國立臺灣大學 === 電信工程學研究所 === 89 === In this thesis, planar periodic structures including microstrip lines and coplanar waveguides (CPWs) are investigated. Spectral domain approach and Floquet's theorem are used to derive the governing coupled integral equations. Method of moment and Galerkin's weighting procedure are applied to convert the coupled integral equations to matrix equations. Global basis functions are used to expand the electric current on the strip and roof-top basis functions are used to expand the magnetic current over the slots. Muller's complex-root searching method is applied to solve the eigenvalue problem.
Two kinds of sonusoidally width-modulated partially loaded periodic microstrip lines are proposed to control the first two stopbands. The dispersion curves of these two partially loaded periodic microstrip lines are obtained and discussed. Numerical results show that by tuning the combination of modulation amplitude and loading factor the first two stopbands can be controlled. Small leakage is also observed and this indicates the existence of the radiation region.
Interdigital-type periodic CPWs are analyzed. Slow-wave and leakage phenomena are clearly observed in the dispersion curves. Increasing the gap of the step junctions, the attenuation and bandwidth of the higher stopbands are greatly increased. Increasing the width of the step junctions, the phase velocities can be slowed down, and the bandwidth and attenuation of the stopbands become large. The large leakage in the radiation region is due to serious discontinuity of this structure and can be used to design leaky wave antenna in the future.
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