Design Of Broadband Dual-polarized Base Station Antenna Element And Antenna Array

With the rapid development of mobile communication technology and the exponential growth of mobile users and communication traffic,the performance of mobile communication systems is becoming more and more demanding.Now the fifth generation mobile communication technology is not yet mature,mobile communication systems are mainly the coexistence of 2G,3G and 4G.As one of the key devices for transmitting and receiving signals in mobile communication system,the performance of base station antenna directly affects the communication quality of the whole system.Base station antenna design has lots of standards,including broadband,dual-polarized,low voltage standing wave ratio,high port-to-port isolation,adjustable electrical downtilt,stable radiation patterns over the whole operating frequency band and so on.Therefore,a dual-broadband,dual-polarized base station antenna with compact structure and adjustable electrical downtilt is designed in this paper.It has not only academic value,but also great market value.This thesis focuses on the broadband dual polarization base station antenna.Firstly,this paper introduces the development background of mobile communication and the research situation of broadband dual-polarized base station antenna.Then,some key parameters of the base station antenna design and antenna array theory are introduced,including the methods of antenna beam forming and the principle of beam downtilt.Secondly,this paper proposed a novel dual-polarized base station antenna element with a operating frequency band of 790-960 MHz.This element adopts octagon-aperture structure and is fabricated by integrated metal casting technology.Two kinds of plastic fasteners are employed on the element to obtain a better impedance matching performance and improve the stability of the structure.In order to further expand the bandwidth of the antenna radiation element,a dual-polarized base station antenna element with a operating frequency band of 698-960 MHz is presented in this paper.A square aluminum sheet is inserted between each pair of adjacent dipoles to improve the impedance bandwidth of the radiation element.Measured results proved that the antenna element has good VSWR,port-to-port isolation and stable radiation pattern at the operating frequency band.Finally,a dual-broadband dual-polarized antenna array with adjustable electrical downtilt is designed in this paper.The antenna array adopts embedded scheme and operates over 790-960 MHz and 1710-2170 MHz.Five lower-band radiation elements and ten upper-band radiation elements are applied in the proposed antenna array.By manipulating input amplitude and phase of each element,0°-14°and 0°-10°electrical downtilt are achieved at lower and upper frequency band respectively.Simulated and measured results demonstrate that the antenna array has good electrical and radiation characteristics at both operating bands and all downtilt angles.The antenna array has practical application value in modern mobile communication system.