| Nowadays,we are in the information age.With the progress of communication system technology,wireless technology is also booming worldwide.Antenna is undoubtedly the most critical device in wireless signal transceiver equipment,because the performance of the transceiver antenna determines the working efficiency of the whole system.In the demand for popularization of indoor small base stations and miniaturization of mobile wireless devices,wireless antennas are required to meet the functions of miniaturization,multi-band,and channel expansion.Therefore,this thesis focuses on antenna miniaturization dual-band technology and antenna multiple input multiple output(MIMO)technology,and completes the design and implementation of compact MIMO antennas applied in the Wi-Fi frequency band.Finally,two WIFI-MIMO antennas for mobile wireless devices and one for indoor small base stations are proposed.The first two models are WIFI-MIMO antennas used in mobile terminal devices.The antennas are both planar inverted F antenna(PIFA)structures improved in microstrip form,printed on FR4 substrate,with a relative dielectric constant of 4.4.The first antenna has a size of 40*20*0.88)8)~3 and operates in the dual band Wi-Fi frequency band with an isolation degree greater than 20 d B within the working frequency band.The second antenna has a small size of 30*30*0.88)8)~3.The innovative method of floor slitting successfully gets the high-frequency radiation when the low-frequency radiation and antenna size are unchanged.The antenna impedance bandwidths are 2.35-2.75 GHz and5.25-5.75 GHz.Besides,the isolation degrees of this antenna are greater than 15 d B,with the maximum value of up to 30 d B on the impedance band.Both antennas have a compact structure.By properly positioning the antenna elements,the two antennas achieve the high isolation level and have good diversity characteristics.The third antenna is a WIFI-MIMO antenna used in indoor small base stations,with an all-metal PIFA structure.The antenna uses the same aperture surface for radiation,so its overall structure is small.By folding,the cross-sectional size of the antenna is reduced,improving the space utilization rate,with the final size of 82*82*13.98)8)~3.In addition,selecting metal aluminum material for processing effectively reduces the overall weight of the antenna,making it more suitable for ceiling or back wall installation.The proposed antenna has a large impedance bandwidth of 2.26-2.5 GHz and 5.5-7.25 GHz,covering the full Wi-Fi6e frequency band.In addition,the antenna has a high gain of 5-8 d B and can radiate omnidirectionally within the impedance bandwidth.On the other hand,the structure of the antenna and the distribution of the center rotation position result in a relatively long distance between the ports,making the isolation between the antenna ports meet the requirements,which can reach even exceed 20 d B in the operating frequency band.Besides,its envelope correlation coefficient is less than 0.03 in the frequency band,and the channel capacity loss is less than 0.3 bits/s/Hz.All indicators meet the requirements of independent operation of each antenna unit. |
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