Optimization Of High Performance Array Antenna For The 5G Communication Based On The Novel Metamaterial

At present,China's 5G communication industry is in its initial stage,due to the requirements of the fifth-generation communication which includes the information transmission speed,transmission delay and information load,make the hardware with the functions of information reception and transmission face more stringent design challenges.Therefore,a large number of antennas including base station antennas,mobile terminal antennas and almost all hardware for mobile communication need to be updated,while in previous generations of communication systems,different types of applications have occupied the frequency band below 6 GHz,which makes the spare frequency band assigned to 5G communication very narrow.In this situation,5G communication is bound to explore and develop the higher frequency bands.This process is accompanied by the developing trend of devices' miniaturization and low costs,so how to design antennas that meet the requirements of 5G communication in the higher frequency band has become a research hotspot in recent years.Based on the practical requirements of 5G communication and the urgency of problems,optimization methods of 28 GHz high-performance transmitarray antennas based on new metamaterials are proposed in this study.The optimization process mainly includes three aspects:Firstly,based on multi-layer gapless gradient metamaterial elements,a coding transmission metasurface is designed.The phase distribution of planar array is derived from the improved rotating paraboloid formula.Therefore,the feed position of transmission antenna array is determined by the equation at the beginning.This gradient coding technology and phase-distribution model simplify the design of transmitarray which has many elements,so a transmitarray working at 28 GHz can be optimized.According to the multi-layer gradient metasurface as the beam focusing array and wideband slot coupling antenna as the feed source,the broadband transmitarray antenna achieves an 11.8% 3 dB gain bandwidth at 28 GHz band,with a maximum gain of 22.6 dB,meanwhile a good low-profile property can be guaranteed,which meets the design requirements of broadband high gain antenna for the 5G communication.Secondly,based on the transmitarray design with single dielectric layer,the high gain and low sidelobe level at 28 GHz are achieved by using symmetrical radiation horn feed.A single-layer dielectric transmission unit cell has two identical radiated structures at the both sides in the propagation direction and four metal rods inserted in the substrate.The additional coupling can be achieved by the rods which breaks through the upper limitation of theoretical phase shift for a transmission unit cell without rods inserted.Hence optimized unit cells with rods inserted can also achieve the 360-degree phase shift for beam focusing with high transmission efficiency.The relative phase distribution of all positions on the array for high gain can be calculated by the formula based on the wave path differences,and the position of feed source can be obtained by the plane wave analysis using the theory of reversible optical path.Then,a symmetrical radiation feed antenna is optimized.The feed antenna and the designed single-layer dielectric planar array form a transmitarray antenna system.The system can achieve 27 dB gain at 28 GHz,and the side lobe level is around-20 dB,which meets the design requirements of 5G directional antenna array.Thirdly,this part of study further optimizes the transmitarray using intelligent swarm optimization algorithm.Based on the second transmission antenna array,the side lobe level is further optimized.Through the joint optimization of transmission coefficient and transmission phase,and according to the fitting curve,the new transmitarray elements distribution is obtained,which reduces the side lobe level of the whole antenna array from-20 dB to-30 dB.Besides the first side lobe,the other side lobes are lower than-35 dB.The optimized transmission antenna array is suitable for the optimization of 5G directional antenna array and has potential values in the application of beam-scanning antennas and multi-beam antennas.