| With the comprehensive issue of 4G licenses in our country, 4G users will show the number of growth spurt, the indoor base station has been widely used for the rapid growth of indoor communication demand, which means the carrying capacity of small indoor base stations face a very high demand. In order to improve the compatibility of the wireless communication system, the mobile station need to implement a plurality of communications bands simultaneously, 2G and 3G coexist, and a small base station is compatible with 4G will be widely demand. Relative to the traditional arrangement of the antenna, the ceiling mounted small base station antenna save floor space, and increases the distance to the users, further reducing the potential radiation hazards. So the research on multiband ceiling small base station antenna has important practical significance.In the traditional horizontal / vertical dual-polarized omni-directional antenna, the size of the vertical polarization unit is often much larger than the horizontal polarization unit, resulting in a size expansion on overall antenna system, not compact enough. But the dual-polarized omni-directional antenna proposed in this thesis, the vertical polarization unit is built in horizontal polarization unit, and also achieves a high isolation and omnidirectional radiation, which is a major innovation. On the other hand, the development direction of WLAN(Wireless Local Area Network) is transmit to beamforming and spatial multiplexing multiplex. The WLAN smart antenna can intelligently adjust the beam direction to the distribution of the user group, increasing transmission channel capacity gain and high density where the direction of the user group located will open up a new field.Combined with business research needs to explore new design on low profile, multi-band, ceiling design of new small base stations, also 4G LTE and other hot spots and trends. Study on multi-band ceiling small base station antennas and design a indoor base station omnidirectional antenna working in LTE2300 / 2500 and GSM1800 / 1900 / UMTS five high frequency to meet the system indicators; and beam switching WLAN antenna working in the 2.4GHz ISM band and 5GHz U-NII band. The main contents are the basic principles of antennas, diversity antenna technology, omni-directional antenna design, beam switching antenna design and conclusion. The main contributions are as follows:1. Based on analysis of antenna pattern, orthogonal polarization diversity and MIMO antenna, aiming at the latest engineering needs, design a new structure of low profile dual-polarized omnidirectional antennas. Putting the horizontally polarized antenna out of vertically polarized antenna leads the horizontal polarization of the design space has been greatly in size and cell structure, which can achieve a wide operating frequency band and good omni-directional, with characteristic of high polarization isolation;2. Depending on the feeding position of horizontal polarization structure, overcome the limitations of the spatial position of the dual polarized structure and design an one-four microstrip power divider with good VSWR, making four ports of horizontal polarization structure be fed simultaneously in time, phase and amplitude, which also simplify the antenna structure;3. Design a 4 beanm switching antenna working at 2.4GHz and 5GHz WiFi band basing on L-shaped bent antenna and N-type excitation oscillator to solve the problem of adjustable omnidirectional beam antenna unit and form a 6 units antenna array, enhancing the directivity of antenna system. |
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