Research On Miniaturized MIMO Antenna For Mobile Terminal

The number of users of mobile communication systems is increasing,and higher requirements are placed on communication capacity and data rate.At the same time,users are pursuing the slimness and full screen of mobile terminals,and the design space reserved for antennas is very limited.The MIMO antenna is a transceiver system composed of multiple antennas,which can make full use of multipath effects to improve channel capacity and spectrum utilization,and thus has received extensive attention.However,there are two major difficulties in applying MIMO antenna technology to mobile terminals.One is how to place multiple antennas in a limited space;the other is how to improve the isolation between multiple antennas in a limited space.In view of these two difficulties,this paper has conducted in-depth research on miniaturized MIMO antennas for mobile terminals.The main contents and innovations of this paper are as follows:(1)The development history of mobile terminals and MIMO antennas is reviewed.The research status of miniaturized antennas,low-coupling antennas and multi-frequency antennas by domestic and foreign scholars is summarized.The related theories and techniques of MIMO antennas are introduced,which provides basic theory and analytical methods for subsequent research.(2)Two dual-band and three-band MIMO antenna structures based on planar monopoles are proposed.For the dual-band antenna,the U-type monopole and U-shaped slot structure effectively extend the current path and achieve a lower resonant frequency while maintaining the same size.At the same time,the T-section is applied between the cells and the double inverted T-slots are etched on the floor reduce the coupling,so that the antenna achieves good matching and high isolation in the 2.24GHz?2.6GHz and 3.38 GHz-3.69GHz frequency bands.For the three-band antenna,the surface current path on the floor is changed by the method of extending the floor and etching the L-shaped groove thereon,thereby adding a new resonant frequency band without increasement of the physical size of the unit,and the isolation is also significantly improved.The antenna finally achieved good matching and high isolation in the 2.73GHz?2.82GHz,3.41GHz?3.63GHz and 4.79GHz?4.93GHz bands.On the basis of theoretical analysis,the actual machining test of the antenna was carried out to verify the effectiveness of the design.(3)Two PIFA-based three-band and four-band MIMO antenna structures are proposed.For the three-band antenna,a new resonant frequency band is introduced by the capacitive coupling feed structure.Since the distance between the units is relatively long and the near-field coupling is small,there is no need to design an additional decoupling structure.The antenna achieved good matching and high isolation in the 2.32GHz?2.5GHz,4.52GHz?5.1GHz and 5.7GHz?6.24GHz bands.For the quad-band antenna,by introducing a lateral microstrip line and a parasitic patch adds two new resonant frequency bands,and by loading the neutralization line and etching the L-shaped slot on the floor to reduce coupling.The final antenna achieved good matching and high isolation in the 1.76GHz?1.88GHz,3.46GHz?3.54GHz,4.71GHz?4.87GHz and 5.74GHz?5.89 GHz bands.