| With the rapid development of mobile communications,there is a sharp increase in mobile data and telephone traffics.Thus the higher system requirements for nextgeneration mobile communication systems are in the urgent need.The frequency bands of 3.3-3.6GHz and 4.8-5GHz have been allocated to the major communication operators in China on November 15,2017.On the one hand,owing to the coexistence of multiple systems,the antenna for 5G communication should own the features such as wide frequency band,high gain,high isolation,etc.On the other hand,in order to provide the large capacity and the high gain,the antenna array and the multiple input multiple output(MIMO)system have to be developed.Furthermore,the characteristic of miniaturization becomes more and more important due to the limited storage space.According to the above-mentioned requirements,three kinds of antennas have been proposed as shown below:Firstly,for the purpose of antenna for wideband and miniaturization,A wideband antenna using metasurface is proposed for the future 5G communications.By using the metasurface and the multi-layer substrate with high relative permittivity,the height of the proposed antenna can be reduced to 0.11? in the operating frequency band.The metasurface including 40 unit cells are arranged on the second layer to improve the gain at the upper frequencies.Besides,by employing the dual arc-shaped defected ground structure,the impedance bandwidth can also be broaden and the gain can be improved.The measured result shows that an impedance bandwidth of 77.2%(1.63-3.68 GHz)with a stable gain of 5.1?1.2 dBi can be obtained.Hence,the proposed antenna is potentially suitable for the future 5G communications.Secondly,A dual-band dual-polarized stacked microstrip antenna with highisolation and band-notch characteristics is proposed.The proposed antenna is comprised of three layers of substrate.To obtain high isolation between two input ports,a pair of orthogonal differentially-driven feeding lines are printed on the top side of the bottom layer.To yield desired lower and upper frequency bandwidths for 5G microcell communications,two sets of 2×2 radiating patch arrays are printed on the second and top layer substrates,respectively.Compared with conventional microstrip antenna,besides demonstrating a smaller size of 0.48?×0.48?×0.085?,the proposed antenna has also exhibited higher isolation of better than 40 dB and higher gain of >8 dBi.Finally,A low-profile metamaterial loaded antenna array with anti-interference and polarization reconfigurable features is proposed for base-station communication.Owing to the dual notches etched on the radiating electric dipoles,an impedance bandwidth of 75.6% ranging from 1.68 to 3.72 GHz with a notch band from 2.38 to 2.55 GHz can be achieved.By employing the metamaterial loadings that are arranged in the center of the magnetic dipole,the thickness of the proposed antenna can be decreased from 28 to 20 mm.Furthermore,a serial feeding network that consists of several Wilkinson power dividers and phase shifters is introduced to attain the conversion between dual-linear polarization and triple-circular polarization.Hence,the antenna could meet the demand of the future 5G intelligent application.With the study of metamaterials,metasurface,reconfigurable antenna and magneto-electric(ME)dipole antenna,three kinds of low-profile,miniaturized and wide-band antennas that are designed with metamaterials,metasurface and so on have been presented for the 5G mobile communication systems.Good performance in different aspects can be achieved and it helps to develop the 5G communications. |
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