| Summary: | 博士 === 國立臺灣大學 === 電機工程學研究所 === 87 === Slot and slot-coupled patch antennas fed by the coplanar waveguide are investigated by using the full-wave analysis based on the Galerkin''s moment method in the spectral domain approach in this dissertation. The coupling slot is etched on the conducting plane of the coplanar waveguide and placed in the direction perpendicular to the transmission line. The equivalent magnetic currents in the coupling slot and in the slots of the coplanar waveguide are all expanded by the subsectional rooftop basis functions, while the equivalent surface electric current density on the microstrip antenna is represented by the entire domain basis functions if necessary. These equivalent currents are solved by the full-wave analysis using the Galerkin weighting procedure, and the reflection coefficient is extracted from the magnetic current distribution on the coplanar waveguide utilizing the matrix pencil technique. All the theoretical results are verified by the measurements and the comparisons show a good agreement between them.
Investigation begins with a wide slot antenna fed by a coplanar waveguide. To model the wide slot accurately, the transverse magnetic current component is introduced and more than one longitudinal components are used across the slot. With this study, we can realize how to model the equivalent magnetic current to get a good agreement between theory and experiment. The variations of the characteristics of the inductive or capacitive slot antennas with parameters such as the slot width, slot length, and center strip width of the coplanar waveguide are presented and their corresponding variations in the bandwidth and the resonant frequency are also discussed.
The spectral domain Green''s functions and the method of Stationary Phase are also used to calculate the front-to-back radiated power ratio for the CPW-fed slot antenna on a single dielectric substrate. A very simple formulation for the front-to-back radiated power ratio is obtained by assuming that the substrate and metalization is infinite in extend. With this formula, the substrate thickness and dielectric constant can be chosen and designed properly for CPW-fed slots.
The same research for the inductive and capacitive patch antenna fed by the coplanar waveguide are also studied in this dissertation. There are more variable parameters such as the slot width, slot length, patch width, and patch length for us to design the patch antenna. The variations of the bandwidth and the resonant frequency with different parameters are also compared to each other.
Finally, a simplified procedure for designing the slot antenna array excited by a coplanar waveguide is proposed. Moment method analysis and matrix pencil approach are adopted to calculate the scattering parameters and hence the self-admittance of each slot. The mutual admittances between the slots are calculated from the formulas derived for the complementary strip dipoles based on the reciprocity theorem and via Booker''s relation. Then the transmission line theory is used to calculate the input impedance of the array, and an iterative process is employed to obtain a matched design for a desired slot voltage distribution. A four-element slot array is fabricated and measured using this design procedure. Calculated results are in good agreement with measurements.
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