| Summary: | 碩士 === 國立交通大學 === 電機學院電信學程 === 103 === For the past few years, there is an growing demand on the bandwidth and data-rate for internet end users. This leads to the need of closely spaced antenna array for MIMO applications. But, the strong mutual coupling between the array antennas in a narrow spacing could dramatically degrade the system capacity if the array spacing is less than . In this thesis, it is shown that this effect can be suppressed by the design of decoupling network.
In this thesis, we proposed a 180 degree hybrid decoupling network which was composed of a 90 degree dual-band branch-line coupler and a 90 degree broadband phase shifter. Therefore, the orthogonal eigenmodes- odd mode and even mode will be realized base on 180 degree hybrid at the side of compact array antenna. Since the mode of odd and even will be independent and de-coupled with each other, we can expect that the radiation pattern of array antenna will be orthogonal if all the ports of decoupling network are matched. If we can excite the orthogonal modes effectively, the decoupling and pattern diversity of this antenna array are achieved. A compact dual-band array antenna is developed to validate the theories above.
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