| At present, Wi-Fi technology develops rapidly and is widely used. Higher requireof Wi-Fi base station antenna is urgent. Inverted-F antenna is a common antenna, buthardly conducted as array unit. By means of analyzing inverted-F antenna in this paper,we found this antenna occupies characteristics of miniaturization, wide band and highgain. Also the radiation pattern is suitable for antenna array. Therefore, aimed atdifferent application request, the paper proposed three kinds of low cost antenna forWi-Fi base station, namely, Wi-Fi base station antenna based on suspended microstrip,miniature Wi-Fi base station antenna based on inverted-F antenna, circular polarizedWi-Fi base station antenna based on inverted-F antenna.Firstly, analysis of common antenna (FR-4epoxy resin board, permittivity is4.6and thickness is1.5mm) is carried out, and the result is this antenna can’t meet the bandrequire of Wi-Fi base station. To expand the bandwidth of Wi-Fi base station antennaand increase the gain, a design of4×1suspended patch antenna array withtaper-structure is proposed. This antenna is feed by a cascaded power divider, microstrippatch using suspended structure for radiation expends bandwidth. By means of gradualchanged and defected structure for ground of feed line, we decreased affection ofresonance frequency from feed line ground to the radiating patch and enhanced the gainat the same time. Simulated results indicate that the antenna bandwidth with suspendedstructure increased about150MHz compared with general microstrip antenna.Measurement of the prototype was carried out and the results state the operating band is2.35~2.59GHz with reflection coefficient less than-10dB (relative bandwidth is8.9%),and half power beam width (HPBW) of E-plane and H-plane is60°and28°respectively.Overall antenna gain achieves12.6dB. All of the testing results have proved theeffectiveness of proposed design the Wi-Fi base station antenna with suspended patchand taper-structure, and the antenna is suitable for Wi-Fi base station.Secondly, this paper applies inverted-F antenna to achieve miniaturization and savecost. Compared to microstrip antenna, impedance bandwidth of inverted-F antenna iswider and can satisfy base station. Analysis of radiation pattern of inverted-F antennawith reflection plate state the side lobe is not too big, and radiation pattern of the arrayis proved to be similar to microstrip antenna by pattern synthesis. Measurement resultsof the prototype state the operating band is2.18~2.66GHz with reflection coefficientless than-10dB (bandwidth is460MHz, relative bandwidth is19.8%), HPBW of planeφ=0°and plane φ=90°are34°and74°respectively. Maximum gain of this antenna canachieve11.5dB. Dimension of FR-4epoxy resin board used is155mm×35mm, is only33.6%of the microstrip array antenna mentioned above. The antenna realizesminiaturization and is suitable for Wi-Fi base station. Finally, the paper improved the antenna on the foundation of inverted-F antennaarray and achieved circular polarization. Though tilting the ground of inverted-Fantenna mentioned above, the surface currents of antenna at vary phases are almost thesame. In addition, the directions of currents continuous change and form a full circle.And then, the antenna will be a circular polarization antenna. Antenna’s operating bandafter forming array is2.31~2.61GHz with reflection coefficient less than-10dB(bandwidth is300MHz, relative bandwidth is12.2%), HPBW of plane φ=0°and planeφ=90°are32°and78°respectively. Maximum gain of this antenna at2.45GHz canachieve11.3dB, while axils ratio is1.2dB. The circularly polarized inverted-F arrayantenna is not only a kind of circularly polarized antenna, but also provides a newparticular thinking for analyzing and designing circularly polarized antenna. In addition,analysis by synthesis of space angle of circular polarization together with the spacedistribution of radiation pattern is a innovation point of this paper. |
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