| The mobile terminal system is developing towards multifunction and the miniaturization and multi-band antenna design of have great research value.Multiple Input Multiple Output(MIMO)antennas can improve channel capacity and spectrum utilization,and the performance of wireless communication networks can improvement.It provides necessary technology for the development of mobile communications,the Internet and the Internet of Things.However,placed multiple antenna elements in a space-constrained mobile terminal will lead to strong coupling.Thereforce,the design of decoupling structure has a great impact on the performance of the MIMO antenna.Because the printed antenna has the advantages of omnidirectional radiation characteristics,small size,low profile,simple structure and easy integration,it is selected as mobile terminal antenna unit.Based on the radiation characteristics of antennas in lossy media,Two multi-band MIMO antennas are designed and analyzed using the simulation software HFSS.The main contents are as follows:1.A three-band MIMO antenna is designed using double neutralization lines structure and reasonable layout of the antenna unit.In addition,the theoretical analysis and experimental verification of the neutralization lines structure are carried out.The loading position and length of decoupling structure are discussed.The antenna is fabricated and tested using epoxy FR4 as the substrate.And experimental results show that the antenna can be cover 2.305-2.4GHz,3.4-3.69GHz and 5.6-5.75GHz.It has high isolation between antenna units,good radiation characteristics and low envelope correlation in the working frequency band.2.A small quad-band printed antenna is designed.According to the principle of meandering,the radiant branches of semi-circular and bending line are choosed to reduce the occupied space of antenna.The T-shaped and G-shaped branches are loaded into the semi-circular branches to stimulate more working modes.Meanwhile discuss the parameters that mainly affect performance of the antenna,and summarize the regulation of working frequency with the parameter.The experimental results show that the antenna is smaller with only 30×18×1.6mm~3 and can cover 2.370-2.483GHz,3.300-3.756GHz,5.395-6.08GHz and 8.01-8.99GHz at the same time.Besides,it has good radiation characteristics and achieves the goals of miniaturization and multi-frequency.3.The quad-band MIMO antenna system is designed based on three hybrid decoupling technologies:floor branch,neutralization line and antenna layout.The hybrid decoupling structure and the main parameters affecting the performance of the antenna are analyzed in depth.And the MIMO antenna is processed and S-parameter tested.The experimental results show that the antenna is small with 30×40×1.6mm~3 and improves the isolation at least 10d B in the multiple working bands.Besides,it has high isolation,good radiation characteristic and low envelope correlation,which can be applied to WLAN(2.4-2.484GHz and 5.725-5.825GHz),Wi MAX(3.4-3.69GHz)and X(8-9GHz)protocols and achieves the design goals. |
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