Aperture-Coupling Excitation and Mode-Coupling Phenomena of Microstrip Leaky Modes
|關鍵字:||微帶;漏波天線;孔徑耦合;模耦合;饋入結構;漏波模;microstrip;leaky-wave antenna;aperture coupling;mode coupling;feeding structure;leaky mode|
This thesis investigates the properties and applications of the first two higher order leaky modes of the microstrip, which include efficient feeding structures, mutual coupling on microstrips, coupling effect in different leaky modes, and several antenna applications. The spectral domain analysis is employed to solve the propagation characteristics of the microstrip leaky modes throughout this study. The first part of the thesis pertains to the first higher order leaky mode (odd mode) of the microstrip line. The design procedure of the microstrip first higher order leaky-mode antenna excited by aperture-coupling method is presented. Separating the radiators from other components with the ground planes provides optimal design of both parts respectively so that the inherent broadband, high gain and frequency-scanning properties of the leaky-wave antenna can be exploited. Tilted- and broadside-beam antennas are designed in X-band. Single and dual beams arrays in K-band and a base-station antenna application for S-band are also implemented. The required elements were reduced markedly in comparison with the patch antenna for higher gain design. Versatile designs combining the merits of multilayer technology offer simplicity and efficient design for many wireless applications. In addition, the coupling effects in the coupled microstrips, which caused by the first higher order leaky mode on the microstrip, are investigated. The resonance phenomena found between the strip of the infinite coupled microstrips are owing to the inner edges of the coupled microstrips forming the resonant boundary and the leaky modes of the microstrips serving as the resonant sources. For even- and odd-symmetry of the coupled microstrips, more than one leaky mode are found in both cases, and these leaky modes couple with each other. The second part of the thesis treats the subjects of the microstrip second higher order leaky mode (even mode). Mode-coupling phenomena of the even modes on microstrip is investigated. These phenomena occur when the dispersion curve of the leaky dominant mode of the microstrip is close to those of the even higher order modes of the microstrip. Interesting patterns of the migration of mode evolution, obtained by varying the ratio of the strip width to the substrate thickness, exhibit the relationships between the even higher order modes and the leaky dominant mode. The spectral gap effect of the even higher order modes is the result of the coupling between these modes and the leaky dominant mode. Design of the even higher order leaky mode as a line source should be based on the physical implications of these phenomena. Short-end CPW and microstrip feeding method are used to excite the second higher order leaky mode. Experimentally exciting the second higher order leaky mode with and without the leaky dominant mode reveals the interference between these two leaky modes.
|Appears in Collections:||Thesis|