| With the development of science and technology,the traditional frequency domain,time domain,airspace and code domain and other spectrum resources are difficult to meet people’s demand for wireless communication capacity,how to effectively improve the system capacity and spectrum utilization rate is the key issue of wireless communication.Carrying the same frequency vortex electromagnetic waves with different orbital angular momentum(Orbital Angular Momentum,OAM)are orthogonal to each other,which can exponentially increase communication capacity,improve spectrum utilization,and have great potential in communication capacity.In addition,vortex electromagnetic waves can also be applied to radar imaging and target detection and other fields,so the generation method of vortex electromagnetic waves has become a research hotspot in the field of electromagnetic waves.The method of vortex electromagnetic waves generation based on the uniform circle array(UC A)requires a complex feeding network,and the feeding network becomes more complex as the number of modes and feeding elements increases.Metasurface can flexibly regulate the phase of electromagnetic waves.Vortex electromagnetic wave generation method based on the metasurface does not require a complex feeding network.The existing vortex electromagnetic wave metasurface antenna cannot be loaded with multimodal vortex electromagnetic waves that can be independently regulated.Two multimodal vortex electromagnetic wave metasurface antenna that can be independently controlled are studied and their performance is simulated based on metasurface technology in this thesis.The main research contents are as follows:1.Based on the polarized rotating metasurface cell,a nested multimodal vortex electromagnetic wave metasurface antenna is designed.First of all,a parasitic patch antenna working at 15 GHz is designed as a feeding cell for the metasurface,and a nested metasurface array with an inner circle nested outer ring is designed,with an inner circle radius of 75 mm,using four feeding units to illuminate the metasurface,the outer ring width was 75 mm,and eight feeding units were used to illuminate the metasurface.The location of the feed antenna unit is designed using the method of the smallest sum of all position distances from the feeding phase center to the metasurface array.+1 modal vortex electromagnetic waveforming is performed on the inner circle area of the metasurface,and+2 modal vortex electromagnetic wave configuration is performed on the outer ring area of the metasurface.Simulation analysis analyzes the difference between the gain pattern,phase distribution plot and modal purity of the inner circle and the outer ring under independent and simultaneous operation,and the results show that the inner circle and the outer ring work do not interfere with each other.And tested the S-parameters of the fabricated antenna.Finally,the characteristics of the vortex electromagnetic waves with the deflection angle are studied when propagating,and the simulation results show that the vortex electromagnetic waves before and after adding the deflection angle show divergence or convergence at a certain propagation distance.2.Based on the polarized rotating metasurface unit,a laminated multimodal vortex electromagnetic wave metasurface antenna is designed.First,two omnidirectional antenna feeds with vertical polarization and horizontal polarization operating at 15 GHz nonroundness of less than 3 dB were designed.The metasurface irradiated by the vertically polarized antenna feeding is loaded with+1 modal vortex electromagnetic wave metasurface,and the metasurface irradiated by the horizontally polarized antenna feeding is loaded with+2 modal vortex electromagnetic wave metasurface loading.The simulation results show that the+1 mode and+2 mode vortex electromagnetic wave supersurface antennas have a gain of 11.65 dB and 10.10 dB,respectively,and a non-roundness of 3.90 dB and 5.37 dB,respectively.Scanning is achieved by moving the feed location. |
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