| With the development of microstrip technology,the microstrip planar reflectarray has been widely used due to its small size,light weight,low profile and easy integration,especially in the field of millimeter wave communication in recent years.These advantages make its application in communication get further attention,but the microstrip reflectarray also has certain defects,such as narrow bandwidth and so on.This shortcoming limits the application of reflectarray in the field of blind coverage in the situation of millimeter wave communication.Based on the problem,this paper studies the design method of broadband reflectarray unit,and uses the new broadband unit to design the reflectarray as the passive repeater to receive and radiate the electromagnetic wave to achieve the effect of blind coverage.The specific research work in this thesis includes the following aspects:1.Firstly,the research background and significance of this topic are introduced.The history of microstrip reflectarray development is traced,and then the advantages of millimeter wave communication are summarized.Then the paper briefly introduces the research status of broadband reflectarray at home and abroad,and has a deeper understanding of the narrow bandwidth of the reflectarray.Then,the research status of millimeter wave indoor blind coverage is introduced,and the feasibility of millimeter wave indoor blind coverage is further understood.The millimeter wave blind coverage in this paper is completed by the microstrip reflectarray.Therefore,the basic theory of the microstrip reflectarray and the design method of broadband unit are introduced,which introduces the theoretical basis for the design of the reflectarray.In addition,the millimeter wave indoor propagation characteristics are briefly introduced,and the composition of indoor signals is understood,which lays the foundation for the subsequent research.2.For the problem of narrow bandwidth of reflectarray,the thesis proposes a new Four Arrows(FAs)unit.By introducing multiple resonances structures,the phase shift range of the FAs unit is greatly expanded.And by introducing the sub-wavelength method,the cell structure becomes more compact and miniaturized,and the linearity of the phase shift curve of the reflectarray unit is improved.Then a reflectarray with a unit number of 12?12 was designed to verify the broadband performance of the FAs unit.The simulation results show that the array has a directivity of 21.8d Bi and a 1 d B gain bandwidth of 22.6%, which proves the effectiveness of the reflectarray broadband technology.Since the array used for the millimeter wave blindness coverage is large in scale and the simulation is slow,the far field pattern of the reflectarray is calculated based on the basic array theory,and three small arrays are designed,and the theoretical calculation is performed.Comparing with the simulation results,it is found that the error of the main lobe directivity is within 1 d B,indicating that the theoretical calculation value can be used to replace the simulation value.Finally,a brief theoretical overview of the design of single beam reflectarray and dual beams reflectarray is given,and three 90?90 arrays are designed.3.The FAs reflectarray is applied to the millimeter wave communication for indoor blindness coverage.The equivalent isotropic radiation power of the reflectarray is calculated based on the radar equation,and analyze the single beam and double beams compensation by using Win Prop and MATLAB joint simulation.The influence of various parameters in the blind situation on the blindness coverage determines the design parameters of the reflectarray,and finally three reflectarrays are processed for actual testing.Theoretical simulation and experimental results show that the proposed broadband planar reflectarray antenna in this thesis has very good characteristics,which can be successfully applied to the problem of eliminating the blind area in 5G millimeter wave indoor communication. |
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