Millimeter Wave Multibeam Antenna Array Based On Multilayer Beamforming Network

Due to the limited spectrum resources of traditional communication band,it has been very difficult to meet the needs of the next generation communication system.Millimeter wave band has gradually become the key point of the research about the next generation communication technology.However,millimeter wave suffers from problems like high transmission loss and interference.In view of this,the research in this paper focuses on the multibeam antenna array based on the beamforming network,which improves the signal-to-noise ratio and data security of millimeter wave communication through the high gain and high directivity beam generated by it.The main contents of this paper include:The necessity of the development of millimeter wave communication technology and the research direction in the field of millimeter wave multibeam antenna in recent years are introduced systematically.The research results about multibeam antenna array working on millimeter wave band during recent years are concluded in this paper and the main work and innovation point of this article are also introduced.The structure and principle of the substrate integrated waveguide(SIW)and the slot antenna array are described in this paper.The design method of the SIW slot antenna array working in the millimeter wave band is given.The Butler matrix is applied as the beamforming network to realize the beam scanning of the slot antenna array.The working principle and design method of the Butler matrix are systematically introduced.Based on the traditional single layer 8×8Butler matrix,an SIW dual-layer 8×8 Butler matrix is designed.The SIW dual-layer8 × 8 Butler matrix is cascaded with the slot antenna array and thus they form a multibeam system.The multibeam system is fabricated and tested.Compared to the traditional single layer 4×4 Butler matrix and 8×8 Butler matrix,multibeam antenna array based on the dual layer 8×8 Butler matrix takes the advantage of simple structure,small size and high scanning precision.Based on the dual layer 8 × 8 Butler matrix,through the optimization and improvement of the original design,a type of improved dual layer 8×8 Butler matrix is presented.The scheme avoids the use of the crossover by the relayout of the overall structure of the Butler matrix.The experimental results show that,compared with theprevious scheme,the improved dual layer 8×8 Butler matrix keeps its size in the same level.Also,it takes the advantage of simpler structure and lower transmission loss.A design scheme of using Rotman lens as a beamforming network to realize the beam scanning of slot antenna array is proposed.The working principle and design method of the Rotman lens are introduced.Based on the traditional monolayer Rotman lens,a dual layer Rotman lens,which works in the millimeter wave band,is designed.The lens is cascaded with the slot antenna array and the multibeam system is simulated and tested.Compared with the traditional single layer Rotman lens,the structure has the advantages of small size,and it has the similar radiation performance as that of the traditional single layer structure.