| The presence of liquid antenna has broken the concept of the traditional solid antenna, and due to its unique characteristics and advantages, it opens up a new field for the antenna theory and application. Liquid antenna is a kind of antenna which uses the liquid material as the radiation element instead of the solid ones. Compared with traditional solid antenna, liquid antenna has unique features and advantages such as high plasticity, reconfigurability, small RCS(radar cross section), improvement in electromagnetic coupling, etcetera, and has great potential in the wireless communication applications, so it is worth of studying. Water as the most common liquid, it not only shares the advantages with other liquids but also offers the additional advantades, such as high permittivity, low cost, transparent, non-toxic and harmless. Water antenna is the most common liquid antenna, but it’s application in wireless communications is restricted due to some defects at present. In this paper, we mainly investigate the reconfigurability, broadband, miniaturization and high efficiency theories and design methods for water antenna, in order to enrich antenna’s theory and design, promote the development and application of new liquid antennas in wireless communications. Finally we have proposed several water antennas for wireless communication. The dissertation was supported by the National Natural Science Foundation of China(61171029) “MIMO Antennas for Mobile Phones”, and(61471172)“The research of new generation WLAN 2.4/5.2/60 GHz compact triple band integrated antennas”, and the main contributions of the dissertation can be summarized as follows:(I) Based on the mechanisms of monopole and Yagi-Uda antenna, a water monopole is designed, and further, we present a frequency and pattern reconfigurable water monopole antenna array. Frequency can be readusted by changing the height of the water cylinder in the excited unit; By combining the excited water monopole antenna and one parasitic elements, then the antenna array is equivalent to a 2-elements quasi Yagi-Uda antenna, and the radiation pattern in the direction of the coordinate axes can be reconfigured; By combining the excited water monopole antenna with arbitrary two parasitic elements that at different coordinate axis, we make a three- units pattern reconfigurable water antenna array and the radiation pattern can be reconfigured in the direction of ?(28)45?/ 135?/-45?/-135?. The antenna has a broad bandwidth and high efficiency in the operating band, and is suitable for the wireless communication system.(II) Based on the dielectric property of the water, two slot coupled stacked water patch antennas are designed, and a method is proposed to realize the antenna’s broadband through modes’ matching. The antenna I works in 13TE?DRA mode and 01 TM patch mode, and antenna II works in 11TE? and 13TE?DRA mode. Through the well-matched modes, the frequency band is broadened and the antennas is efficient, optically transparent and aesthetic.(III) Based on high dielectric constant properties of water, we make water as a dielectric loading in a antenna to decrease antenna’s sizes, then a water-loaded antenna for mobile phone is proposed, the overall size of the antenna is 0.025? ?0.1? ?0.01? at the frequency of 890 MHz, and capable of GSM/DCS/PCS/UMTS operation. For frequencies in the GSM band, the antenna gain is about-0.82 to 0.15 d Bi, efficiency between 31%- 50%, whereas that for the DCS/PCS/UMTS bands ranges from about 1.13 to 3.28 d Bi and the efficiency between 64.5%-89.5%. |
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