Design Of Wideband MIMO Directional Antennas For Indoor Distributed Antenna Systems

With the progress and development of mobile communication technology in recent years,the consumers put forward higher requirements on the covering area and the signal quality of the mobile communications network.Because the reinforced concrete structure of modern buildings absorb and shield the signal of the base stations in the outdoor,the loss of the radio wave is very large.So the signal that the mobile terminals indoor receive from base station in the outdoors is very weak,which may lead the indoor users cannot use the mobile terminals normally.In addition,the mobile terminals can be used normally inside of some buildings,but the density of users is very large and the base station channel is crowded,thus,the mobile terminals couldn't be connected.Adopting the indoor distributed antenna systems can solve this problem.Because the indoor distributed antenna systems can distribute the base station signal evenly in every corner of the room.In case of kind,this thesis proposed several wideband directional antennas and wideband MIMO directional antennas which can be used in the indoor distributed antenna systems.1.The design of dual-wideband directional magneto-electric dipole antenna.This thesis proposed dual-wideband directional magneto-electric dipole antenna and dual-wideband dual-polarized directional magneto-electric dipole antenna by studying the typical magnetoelectric dipole antenna.Those two antennas cover dual bands from 0.8 to 0.96 GHz and 1.7 to 2.7 GHz,which are adopted by three major mobile operators in domestic.We adopted the ?-shaped parasitic strips to improve the impedance matching of low frequency band and analyzed the reasons that effect the radiation characteristic of the antenna in the low frequency band.According the simulated two antenna models,we fabricated them and measured them.The measured and simulated results are in good agreement.They all can be applied in the indoor distributed antenna systems.2.The design of dual-wideband dual-polarized directional MIMO antenna.Firstly,we proposed a new type dual-wideband dual-polarized directional magneto-electric antenna.The antenna employs a parasitic metallic loop and four side walls with same obliquity along each edge of the square reflector.The antenna demonstrates good directional radiation performance,stable gains and cross polarization characteristics in the whole frequency bands.On the base of the dual-wideband dual-polarized directional magneto-electric antenna,we used it to form 2×2 MIMO array.Different heights side walls which are placed between two antenna elements are employed to increase the isolation between antenna elements with the same polarization.Those two antennas also cover dual bands from 0.8 to 0.96 GHz and 1.7 to 2.7 GHz,which are adopted by three major mobile operators in domestic.We fabricated those two antennas basing on the simulated models and measured them.The measured results agree well with the simulated ones.3.Dual-wideband dual-polarized directional MIMO antenna with band-notched characteristic is discussed.Firstly,a dual-band single-polarized directional magneto-electric dipole antenna with band-notched in Wi Fi 2.4 GHz was realized by etching U-shaped slot on the radiation patches of the magneto-electric dipole.Then we designed a dual-band dualpolarized directional magneto-electric dipole antenna with band-notched characteristic.Using equal length feeding strips can make the S parameters of two ports of dual-polarized antennas have better consistency.Finally,we used the dual-band dual-polarized directional magneto-electric dipole antenna with notched characteristic to form 2×2 MIMO array.Similarly,different heights side walls which are placed between two antenna elements are employed to increase the isolation between the same polarization antenna elements.The working frequency bands of those three antennas are same with above antennas except for the Wi Fi 2.4 GHz frequency band which is notched.The simulated results show those antennas having good directional radiation performance and cross polarization characteristics.The antennas with the band-notched in Wi Fi 2.4 GHz(2.4~2.48 GHz)applied in MIMO communication systems can improve the anti-interference characteristic of whole systems.