Design And Performance Of Dual-polarized Base Station Antenna

The continuous development of modern wireless communication technology has promoted the improvement of people's work efficiency and life quality,but also puts forward higher requirements for communication capacity and communication rate.And as a very important part of that,the performance of base station antenna always plays an important role in wireless communication system.With the rise of the fifth generation mobile communication system characterized by high spectrum utilization and intelligent allocation,the study of base station antenna in 5G band has well on its way to become a front-burner issue at present.Dual polarization antenna has been widely used in the development of base station antenna because of its advantages such as saving the number of antennas,reducing the investment cost,having low requirements on site selection,convenient and installation,and ensuring diversity.Combined with the specific needs of current mobile communication,aiming at the commonly used Wifi,LTE and 5G frequency bands,based on the basic theory of base station antenna,this thesis uses electromagnetic software HFSS to carry out design and simulation work,and designs five types of double-polarized base station antenna:1.Aiming at 5G millimeter-wave frequency band,this thesis firstly designs a dual-polarization slot coupling stack patch antenna unit working in millimeter-wave frequency band.Under the condition that the port reflection coefficient is less than-15d B and the isolation between the two ports is greater than 40d B,the antenna unit can achieve the working bandwidth range of 26.2-30.4GHz,and the gain can reach about 5d Bi.Based on the designed antenna unit,antenna arrays of 1×8 and 4×8 are formed,and the antenna arrays are fed regularly with the method of constant amplitude and different phases.The simulation results show that the maximum scanning deflection Angle of 60°can be achieved under the condition that the gain drop is not more than 3d B.And for the 4×8antenna array for the physical processing and testing,although the test results compared with the simulation results have a certain degree of decline,but also verified the feasibility of the structure designed in this chapter.2.Based on the advantage of stepped Barron feed structure in impedance conversion,a multi-mode broadband±45°dual-polarization base station antenna is designed,which is also suitable for LTE and 5G applications.By introducing an embedded ring into the original square ring dipole,a new resonant mode is formed at higher frequencies on the premise of keeping the original size of the antenna unchanged.The new resonant mode is integrated with the original low-frequency and medium-frequency resonant modes,which successfully expands the working bandwidth of the antenna.The antenna operates in the2.23-3.78GHz frequency band,the port reflection coefficient is less than-15d B,the isolation degree is higher than 30d B,the gain can reach 8.8±0.7d Bi,and the half-power beam width is stable in the range of 65±6°.3.The second antenna designed in this thesis is a multi-mode broadband±45°dual-polarized base station antenna suitable for LTE and 5G frequency band applications,and the antenna unit is fed by coaxial cable.By introducing the folded circular ring dipole with short wires into the stepped square ring dipole,a new resonant mode is formed at high frequency without increasing the antenna size,and the working bandwidth range is extended.And has carried on the real processing and the test work,simulated and measured results show that the antenna to meet|S11|<-15d B and|S21|<-25d B conditions,can achieve 55.9%(2.28-4.05 GHz)relative bandwidth ratio,the measured gain within the working frequency band of about 8.3±0.9d Bi,cross polarization ratio greater than 25 d B,the design of the box reflector makes the half-power beam width in the horizontal plane stable within 62±5°.4.The fourth antenna designed in this thesis is a low profile dual-frequency dual-polarization base station antenna loaded with AMC reflector plate.Based on the zero-phase reflection characteristic of artificial magnetic conductor(AMC)surface,an AMC element with hexagonal inside and circular outside is designed,and a 4×4 periodic structure is formed.It can be used as a metal floor in the base station antenna,so that the antenna element can achieve low profile and good one-way radiation characteristics.The final antenna can achieve the Wi Fi dual-band working effect of 2.31-2.61GHz and5.13-5.5GHz,and the final profile height of the antenna is only 12.5mm(0.1 free space wavelengths at 2.4GHz).5.The method of reducing the profile height of broadband antenna is studied.In the design of the antenna element,a circular arrow patch is added to the four corners of the orthogonal ring dipole,and a double-layer square ring metal patch is loaded above the antenna element to act as a parasitic element,so that the antenna element can obtain better impedance matching effect.Based on the 4×4 periodic regular octagon AMC structure,the overall height of the antenna is successfully reduced,and the profile height of the antenna designed is about 0.156?₀(?₀ represents a wavelength corresponding to the center frequency point in the operating frequency band).Under the condition that the port reflection coefficient is less than-10d B and the degree of isolation between the two ports is higher than 20d B,the antenna's working frequency band covers 2.3-3.9GHz,and it is suitable for LTE and 5G frequency band applications.