| Summary: | 碩士 === 高雄師範大學 === 光電與通訊工程學系 === 98 === Two compact MIMO antennas, designed for WLAN/WiMAX system applications, are presented in this thesis. The first MIMO antenna system is composed of three triple-branch loop antennas. Each triple-branch loop antenna is excited by electromagnetically coupled feeds, and all triple-branch loops are designed to be half-wavelength resonant structure, thus achieving the miniaturization of the antenna size. Good impedance matching over the 2.4, 3.5, and 5 GHz bands for the three branch loops can be easily achieved by properly choosing the coupling gaps and coupling positions. The experimental results show that a sufficient distance between any two triple-branch loop antennas is needed for achieving good isolation. The second MIMO antenna system consists of two symmetrical monopoles. The design of bending the monopole into a U-shaped structure is applied for size reduction, and the impedance matching is achieved by adding the shorting strip. Also, dual-frequency operation in the 2.4 and 3.5 GHz bands can be obtained by embedding an open slot into the monopole. Furthermore, the isolation can be performed well even when a small distance between the two monopoles is used.
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