MIMO Antenna Research And Design For Obile Devices

Multiple antenna technology, such as Multiple-Input Multiple-Output (MIMO), was putforward as a new technology for improving spectrum utilization in1990s. In recent years,because of the scarcity of spectrum resource, MIMO technology has become a hot researchtopic. In wireless communications, MIMO antenna technology, using diversity principle tocreate multiple parallel channels for data transmission, improves system spectrum efficiencyand capacity of wireless communication while not increasing the power and spectrumresources. At the same time, MIMO and OFDM also become one of the core technologies forthe next generation communication systems. Multiple antenna technology has been widelyapplied in base stations, but not in mobile devices because the design of a small MIMOantenna with low-coupling and low-correlation in the mobile device of the limited size is verydifficult. In addition, due to the different demands on mobile device functions, the wirelesssystem that can operate in multiple bands has also come up. The design and research ofmultiple band MIMO antenna is also becoming a hot research topic.First, this thesis systematically overview the parameters of MIMO antenna which areused to evaluate MIMO performances based on the basic antenna knowledge. The isolation,correlation coefficient, mean effective gain and so on are briefly introduced for furtherresearch.Then a MIMO antenna covering2.4GHz band is proposed. The isolation betweenantenna elements can be improved by loading the coupling patches and slots. Meanwhile,another MIMO antenna covering2.4GHz band is also proposed. The isolation is improvedbecause of the low coupling between monopole antenna and slot antenna. The two antennashave good isolation and correlation coefficient, thus ensure good MIMO performance.Finally a miniaturized dual-band MIMO antenna covering WLAN2.4GHz and5.8GHzbands is proposed. In this antenna, a connecting ground-shorting pin and a patch areintroduced to improve the isolation. Triple-band MIMO antennas covering WLAN2.4/5.1/5.8GHz and WiMax2.5/3.4/5.2GHz are proposed. Simulation shows that these MIMO antennascan provide good MIMO performance.