Research On Artificial Electromagnetic Metamaterial And Its Application In Microwave Power Transmission

Microwave power transmission(MPT)is the wireless power transmission at microwave frequencies from one location to another.The transmission process involves the conversion of DC power to microwave energy at the transmitting end,the microwave power transmission between the transmitter and receiver,and the collection of microwave energy and conversion into electricity at the receiving end.The MPT technology has been widely used in space solar power station,near-space vehicles and other fields,and it has become the research hotpot at home and abroad.Related tightly to the pre-research project entitled “Microwave Power Transmission and Its Application”,the dissertation presents the research on related technologies of artificial electromagnetic metamaterials,which starts with the realization of a higher microwave capture efficiency in complex environment.The main contents of the dissertation could be summarized as follows:Firstly,two energy-absorbing structures are proposed to investigate the energy absorption mechanism of metamaterials.Starting from the three-band absorber,the surface current and field distributions are analyzed to reveal the multi-band absorption mechanism.In particular,a high-order dipole resonance is realized within the designed structure.On the basis of multi-band absorption,the absorption bandwidth is expanded and the absorption performance is also improved by loading lumped resistances into the multi-resonant structure.By analyzing the wideband absorption,it is concluded that the energy dissipation caused by lumped resistances does not play a key role in the whole energy absorption process.And the research laid the foundation for the design of microwave energy harvester.Secondly,two energy-harvesting structures are also proposed to investigate the energy harvesting mechanism of metamaterials.Based on the rotationally symmetric topology,the analysis of surface current distribution and the energy dissipation distribution within the unit cell,which fully show that the lumped resistance plays a crucial role in the whole energy harvesting process.High performance energy harvesting for arbitrary polarized incident waves can be achieved by using the designed harvester.Compared with linear polarization,circular polarization is more suitable for microwave power transmission between moving objects.The mechanism of selective energy harvesting for circularly polarized waves is analyzed,and the high-efficiency energy harvesting for right-handed circularly polarized waves is achieved.And the research has guiding significance for the miniaturization and integration of microwave energy harvesting system.Finally,traditional antennas are used to capture microwave energy,but they have certain performance defects.Therefore,metamaterials are used to optimize the performance of traditional antennas.Under the condition of circular polarization excitation,the co-polarization reflection and cross-polarization transmission mechanisms are analyzed.According to the rotation phase gradient principle and the generalized Snell's law,phase gradient metasurfaces are constructed to realize the flexible control of the beam direction of the reflected or transmitted waves.In addition,the overall performance of the antenna system is improved obviously by assembling the focusing metasurface with the traditional antenna.The research provides new ideas for improving the performance of traditional microwave devices.