Research On The Base Station Antenna And Its Array With Reconfigurable Patterns

With the rapid development of wireless communication systems,antenna research is now moving to multi-function,high integration,and intelligence.However,the traditional antennas have only fixed functions and cannot meet the increasingly diverse needs.Therefore,reconfigurable antennas with multiple functions have attracted attention.The pattern reconfigurable antenna can expand the signal coverage area by adjusting the deflection direction of the pattern.The dual-polarized base station antenna has a relatively high channel capacity.Therefore,the research on the reconfigurable pattern of the dualpolarized base station antenna has broad application prospects.Secondly,the pattern reconfigurable base station antennas make the radiation range of single base station antenna larger,so only a small number of base station antennas are needed to cover signals in a specific area.The pattern reconfigurable base station antennas not only area wider,but also saves costs.Therefore,according to the current wireless communication system's requirements for large-capacity,multi-functional antennas,this thesis studies the pattern reconfigurability and its array characteristics based on dual-polarized antennas.The details are as follows:1.The pattern of base station antenna can be reconfigurable by loading adjustable reflective metasurface.In this thesis,a cross-dipole type dual polarized base station antenna is designed.Then,a 2×2 square parasitic patch is introduced on the floor of the base station antenna,and two varactors are loaded on each parasitic patch to control the pattern of each polarization.By using a parasitic patch tuned by a varactor-diode,the antenna can continuously manipulate the pattern in E-plane and H-plane.The maximum beam scanning angle of Eplane and H-plane can be observed to be greater than ±25°.The reconfigurable principle of the pattern is given.That is,each polarized dipole antenna and the surrounding parasitic square patch can be regarded as a three-point source.The central source is the driven source,and the two surrounding parasitic sources are the parasitic sources.When the phase of the parasitic source is changed,the pattern of the main beam will be deflected.It is proved that the pattern reconfigurable antenna can be realized when the unbalanced capacitance is introduced.2.The pattern of base station can be reconfigurable by loading transmission parasitic structure.Firstly,a dual polarization base station antenna based on patch is designed.Then,a parasitic branch loaded with PIN diode is introduced near the space domain of the base station antenna.By adjusting the state of PIN diode,the pattern of base station can be reconfigurable.Three parasitic forms are given,which proves the feasibility of the transmission type antenna pattern reconfigurable.By means of transmission type reconfigurable pattern,the base station antenna can scan the pattern in H-plane in a wide frequency band,and the range of scanning angle is about ±50°.Therefore,the reconfigurable pattern of transmission type has good performance.3.Base station array based on pattern reconfigurable antenna.Firstly,based on the generalized principle of pattern multiplication in array antenna,the function of pattern reconfigurable antenna in array is proved theoretically by using MATLAB simulation method.Then,the pattern reconfigurable antenna can be reconstructed to form an array.The effects of several parasitic structures on the performance of the array are analyzed,and the best parasitic structure to improve the array performance is selected.Finally,the performance of the array composed of common antenna and the array composed of pattern reconfigurable antenna is compared,and the design advantages of this paper are highlighted.