Design Of Closely-spaced And Shared-aperture Base Station Antenna Array In Mobile Communication Systems

With the development of mobile communication systems,people have higher requirements on the quality of communication,so the development of base station antenna is changing with each passing day.The large-scale multiple-input multiple-output technology applied on the base station has become one of the hot research directions because it can significantly improve the system capacity.However,this technology puts forward higher requirements on the isolation characteristics and radiation performance of the base station antenna.In the future,multiple communication systems will coexist.The method of shared-aperture placement has attracted much attention due to its greatly improved space utilization.This thesis firstly summarizes the current research status of the base station antenna.Then,according to the requirements of closely-spaced and shared-aperture base station antennas,three base station antenna arrays are designed based on the theory of antenna.Firstly,a closely-spaced base station antenna array with high isolation is proposed to solve the problem of mutual coupling between elements.The distance between adjacent elements is 0.49λ_3.5G(λ_3.5Gis the free-space wavelength of 3.5GHz).Coplanar loading of artificial electromagnetic material above the antenna increases the refractive index of the upper-medium so that the beam converges in the axial direction,the energy coupled to other elements is reduced,and the isolation between the elements is improved.Metal baffles are loaded to obtain good radiation characteristics.The antenna array works in the 3.4-3.6GHz frequency band（VSWR<1.5）.The isolation between elements is greater than 22.5d B.The half-power beamwidths of the horizontal and vertical plane are 77±10°and 76±4°,respectively,and the broadside gain is 6.8±0.7dBi.Secondly,a broadband closely-spaced base station antenna array is proposed for the problems of beam broadening and severe ripple jitter of closely-spaced broadband antennas array.The distance between adjacent elements is 0.51λ_2.2G(λ_2.2G is the free-space wavelength of 2.2GHz).First,three layers of dielectric superstate above the array are loaded to compress the beamwidth on the horizontal plane.Next,metal baffles are loaded to reduce the sidelobe level and improve the front-to-back ratio.Grooves are made to reduce the ripple jitter in the pattern.The antenna works in the 1.7-2.7GHz frequency band（VSWR<1.5）,the polarization isolation of the edge and middle elements are higher than 17d B and 15d B,respectively.The half-power beamwidth in the horizontal plane is 62±5°and 66±9°and the gain are 7.8±1.5dBi and 8.2±1.5dBi,respectively.The front-to-back ratio is higher than20d B.Finally,a shared-aperture dual-band dual-polarized base station antenna array with operation bands of 0.69-0.96 GHz（LB）and 3.3-3.8 GHz（HB）is proposed in this letter.Within the same antenna aperture,magnetoelectric dipole antenna（MEDA）as low-band antenna（LBA）and crossed dipole antenna（CDA）as high-band antenna（HBA）are designed.On one hand,mental MEDA as main body makes the antenna array stable,on the other hand,MEDA can naturally achieve stable radiation performance in the LB.To recover the distortion of radiation patterns in the HB,frequency selective surface structure is introduced.An antenna array prototype has been manufactured and measured.The cross-band isolation is higher than 30d B without any extra decoupling structures.The half-power beamwidths of the LBA and HBA are 66.5±2.5°and 60±5°,respectively.The broadside gains are 8.4±1.2dBi and9.5±0.5dBi,respectively.