Miniaturization Of 5G Base Station Antenna With Large Scale And High Density

5G enhanced mobile broadband application scenarios emphasize to achieve 10-100 times of data throughput with higher spectral efficiency,lower delay and higher reliability.To achieve this,Multiple-Input Multiple-Output(MIMO)technology can be used on both sides of the base station and the terminal.As the number of antenna elements increase gradually,the size of the base station antenna array will be further enlarged,which will increase the production and maintenance costs of the base station system.Base station systems usually use dual-polarized antennas to increase channel capacity,therefore,the overall size of the antenna array can be reduced through the miniaturized design of antenna units and the compact arrangement of antennas.Due to the reduction of spacing between antenna units,the coupling between antenna ports become stronger,it is necessary to introduce decoupling technology in the MIMO array to reduce the mutual coupling between antennas.This paper mainly studies the miniaturization of dual-polarized antenna and the decoupling technology of MIMO antenna arrays.1.A novel broadband miniaturized high islotation dual-polarized antenna is proposed.(a)Firstly,two orthogonal dipoles fed by microstrip balun can realize±45°dual polarization mode.The results show that the VSWR<2 of the dual polarization antenna,the isolation of the port is more than 30d B,with the antenna size of 56×56×40 mm~3 in the band range of1.71-1.92 GHz.(b)Then,in order to reduce the size of the antenna unit,the end of the antenna arm is bent down by analyzing the surface current distribution of the antenna arm,so that the antenna size is reduced to 49×49×40 mm~3,and the VSWR<2,the port isolation is greater than 25 d B in the band range of 1.71-1.92 GHz.(c)Finally,multi-section impedance transformation is designed on the microstrip balun feed structure,and the relative positions of the two baluns are changed at the same time,so that the antenna can work in the bandwidth of 1.71-2.17 GHz,the VSWR<2,and the port isolation is 36 d B,which realizes the broadband and high isolation design of the antenna unit.The overall size of the antenna is further reduced to 45×45×35 mm~3,and the volume is reduced by 43%,realizing the broadband,miniaturization and high isolation design of the dual-polarized antenna.2.The decoupling principle,implementation method of Artifical Dielectric Layers(ADL)and its influence on antenna pattern are introduced in detail.(a)Decoupling principle and implementation method of ADL are introduced,and a design example is given.(b)Analyzed the electric field distribution after introducing ADL dielectric board above the antenna and the influence of relevant parameters of ADL on different polarization coupling of MIMO antennas,then,the feasibility of applying ADL to MIMO antennas decoupling is verified.(c)On the basis of reducing the mutual coupling of MIMO antennas by introducing ADL,the influence of the shape of ADL on the antenna pattern is further analyzed,and the method of suppressing the cross polarization ratio by introducing a double-layer hollow ADL above the antenna are proposed.3.Using ADL decoupling technology in two kinds of MIMO arrays with different spacing,the isolation between ports is improved and the antenna array size is reduced.(a)Massive MIMO antenna decoupling design based on Frequency-division Duplex(FDD)mode.Firstly,receiver(Rx)and transmitter(Tx),operating frequency bands are 1.71-1.92GHz and 1.93-2.17GHz,are designed.Secondly,in order to realize the compact arrangement between the MIMO antennas array,the Rx and Tx linear arrays are arranged in staggered arrangement,then,introducing multiple one-to-three feed networks to design a 6×6 MIMO array antenna,in which the row spacing between adjacent antenna elements is 0.35?,and the column spacing is 0.3?(?is the wavelength corresponding to 1.95 GHz).However,mounting the discrete metal partition on MIMO antenna array can not meet the requirement of decoupling,ADL is introduced above the antenna to achieve decoupling.Finally,the feasibility of the decoupling method is verified by manufacturing and testing the 6×6 MIMO array.(b)A more compact high-density array antenna is designed and decoupled by double-layer ADL.Firstly,a dual-polarized antenna with a working bandwidth of 1.71-2.17 GHz is used as an array element,and a 5-element MIMO antenna is designed according to the staggered arrangement,in which the row spacing between adjacent antenna elements is 0.4?and the column spacing is 0.25?(?is the wavelength corresponding to 1.8 GHz).Secondly,metal pillars are loaded in the MIMO array and the double-layer hollow ADL is used to improve the isolation between all ports.Finally,based on the 5-unit MIMO antenna,it is expanded to a 5×4 MIMO array through one 1/4 equal radiation in-phase power dividers to realize the miniaturization of the MIMO arrays.