| Summary: | 碩士 === 正修科技大學 === 電子工程研究所 === 97 === This study mainly focused on antenna designs for WiMAX applications. In practical applications, broadband antennas use multiple-input multiple-output system to increase the transmission speed. Also, filters are used to suppress unwanted bands. Both the strategies will lead to increasing difficulty and cost. Therefore, this study proposes several novel designs. First, a broadband monopole antenna design is presented. This design reduces the antenna dimension and increase bandwidth by the capacitive coupling between the radiating patch and the ground plane. Second, the first proposed design was applied in the multiple-input multiple-output (MIMO) system. Because coupling between the radiating patch and the ground plane is reduced, the MIMO system has good isolations between antennas. By adding two current paths opposite to the proposed broadband patch antenna, the operating bands in WiMAX 2.5/3.5/5.8 GHz is presented. The forth study proposes a chip antenna for WiMAX2.5/3.5/5.8 GHz operation. The current path is increased by stacking structure. Also, an additional resonant mode is generated through the coupling effect between the radiation patches to broad the operation bandwidth to meet the requirement of WiMAX system.
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