الفهرس | Only 14 pages are availabe for public view |
Abstract This thesis aims to solve the problem of the relative narrow bandwidth of the branch-line coupler (BLC) and its relatively large size by taking the advantages of the properties of the Composite Right/Left-handed metamaterials (CRLH) and its duality (D-CRLH). The following theoretical and practical investigations on conventional as well as metamaterial two-section branch-line couplers are presented. 1. Starting with a detailed analysis of a two-section BLC with an arbitrary power division ratio, closed-form expressions for the characteristic impedance of the coupler arms and the scattering parameters were derived. The derived relations are required for the designs of the proposed couplers. 2. Based on the derived relations, and the artificial transmission line concept, a proposed 3 dB two-section BLC was designed, simulated, and fabricated using the microstrip technology. The simulation was carried out using the Advanced Design System (ADS) circuit simulator and the Computer Simulation Technology (CST) electromagnetic simulator. The corresponding conventional microstrip coupler was also designed and simulated for the sake of comparison. 3. Also, a proposed metamaterial (D-CRLH) two-section BLC was designed at a frequency of 1.8 GHz, simulated, and fabricated. For this purpose, a D-CRLH Vshape coupled-line unit cell was suggested and analyzed. Then, unit cells for the coupler arms were designed and simulated. A comparison between the simulated and measured results of the proposed coupler was carried out. 4. The study was extended to apply the proposed metamaterial coupler into a wideband balanced amplifier, which is a common microwave circuit component. Therefore, a microwave transistor amplifier was also designed and simulated using the ADS circuit simulator. The simulated results of this amplifier and the balanced amplifier were obtained. |