Research And Design Of Ku Band Electromagnetic Focusing Lens Based On Metasurface

In recent years,the satellite communication system frequency band has gradually shifted to the higher frequency such as Ku-band in order to meet the needs of channel bandwidth and transmission rate.Metasurface lenses can reduce the impact of path loss such as rain and snow fading in Ku-band without increasing the transmitting power,and improve the efficiency of the signal.Therefore,it is of great academic significance and application value to carry out the research and design of Ku-band metasurface lenses.In this paper,based on the analysis of the theory and research status of transmissive metasurface lens design,the main work carried out is as follows:Firstly,a three-layered dielectric stacked phase-gradient metasurface focusing lens is designed with the multilayer metasurface technique.Based on the classification study of periodic surface cells,the adaptation of the cells to irradiated wave conditions such as polarization and incidence angle is considered.A nested combination of toroidal and circular cells is used as the metasurface cell.The effects of the number of layers and incidence angle on the transmission amplitude and phase of the metasurface cell are investigated.The lens size and focal length are determined according to the need,and the phase distribution on the metasurface is obtained based on the gradient phase compensation method.The performance of the metasurface lens is simulated and analyzed by combining the planar wave feed source and the patch antenna spherical wave feed source.In addition,a sample is fabricated and measured.The results show that the metasurface lens can achieve plane wave focusing at 13 GHz with a 3 d B focal spot diameter of about 17 mm,which can increase the gain of the microstrip antenna from 6.9 d Bi to 18.6 d Bi.In addition,the proposed lens could maintain good focusing performance even when the feed source is tilted at incidence.Secondly,to address the problems of dielectric loss and inconvenience of processing caused by multi-layer dielectric stacking,a double-layer metasurface focusing lens with multiple operating frequency is designed using a dielectric discrete unit.Based on the principle of open resonant ring,a deformed"I"type and double"T"type capacitive coupling arm structure is designed as the metal layer of the metasurface unit.A 360°transmission phase coverage is achieved by using two types of unit segmental coverage which could complete the complementary transmission amplitude of different frequency bands.The design of a 170×170×5 mm~3metasurface lens with a focal length of 40 mm was achieved by discrete treatment of the unit medium to increase the design freedom,reduce the number of layers and lower the loss.Simulation and test results show that the focusing function for x-polarized waves can be achieved in the 14-16 GHz band.At the center frequency of 15 GHz,the transmittance of the unit is around 0.83 and the array focuses well,with a 3 d B focal spot diameter of about 22 mm.The simulation and test results show that the focusing function for x-polarized waves can be achieved in the 14-16 GHz band,with a better focusing effect at 15 GHz and a 3 d B focal spot diameter of about 22 mm.Finally,to further improve transmission efficiency,a broadband high transmission metasurface focusing lens has been designed using a dielectric-free all-metal metasurface unit.By combining the deformed"I"and double"T"metal structure,the phase of the transmitted wave is adjusted 360°by optimizing the layer spacing.The accumulated phase is generated by air and the sudden phase change is generated by the metal structure.The all-metal metasurface lens significantly improves the transmission efficiency.Simulation results show that the lens can effectively convert spherical waves into plane waves and achieve focus of x-polarized waves in the 14-16 GHz;The focus is achieved with the cell transmission amplitude around 0.93 at 15 GHz and a 3 d B focal spot diameter of about 12mm.