New Reflective And Transmissive Artificial Electromagnetic Metasurfaces And Their Applications

The artificial electromagnetic metasurface(MS)is an array of artificial microstructures composed of a series of subwavelength unit cells with periodic or aperiodic arrangements,which can realize flexible regulation of the electromagnetic waves by arranging the unit cells in an orderly manner.Based on the research of reflection MS,transmission MS,and transmission-reflection MS,this dissertation aims at different application fields for finding the research points and innovative points.For satellite communications,circular polarization(CP)waves are often selected as the information carriers to achieve wireless communications between different base stations in different frequency bands.Therefore,realizing independent regulation of multi-band and dual CPs has important application value for satellite communication systems.For vortex beam regulation,the combination of mode multiplexing,polarization multiplexing,and orthogonal frequency division multiplexing technology has shown important research value in wireless communication,imaging,and information encryption.For the full-space multifunctional system,integrating multi-function and achieving full-space beam scanning and beam switching provide a new method for system integration and full-space communication.The specific research content of this dissertation includes the following aspects:1.Research and design of the reflective MS operating at multi-band and dual CPs.Three types of reflective MSs are designed by introducing the spin decoupled strategy.Adopting the frequency selective surface(FSS),the first reflective MS suppresses the mutual coupling between the unit cells operating at multi-band,thereby realizing the independent control of the dual CP beams at different frequency bands.At the same time,the calculations of the aperture efficiency(AE)and far-field radiation pattern of the reflective MS provide theoretical support for further improving the AE of the MS and verifying its far-field radiation characteristics.The final measurement results are in good agreement with the calculation results.Adopting the single-layer unit cell with a nested structure,the second reflective MS solves the problem of the first reflective MS with a high profile caused by loading the FSS.By comprehensively considering the mutual coupling between unit cells operating at different frequency bands,the 2-bit phase coding strategy for K unit cells and Ka unit cells is designed.Finally,the independent control of the dual CP beams is realized at K-and Ka-bands.At the same time,by adopting the same unit cells with nested structure,the multi-polarization(including left-handed CP,right-handed CP,x-polarization,and ypolarization)insensitive MS operating at dual bands is designed.The third reflective MS suppresses the mutual coupling between the C unit cell and K / Ka unit cells by loading the FSS.Simultaneously,the K / Ka unit cells adopt the single-layer nested structure to realize dual-band operation.Thereby,the independent phase control of the C-band,K-band,and Kaband unit cells could be realized.Subsequently,the C unit cell,K unit cell,and Ka unit cell adopt 3-bit,2-bit,and 2-bit phase coding strategies,respectively,to form the reflective MS.Finally,the independent regulation of the dual CP beams is realized at C-band,K-band,and Ka-band.2.Application and research of the multi-band and spin-decoupled reflective MS for vortex wave regulation.By adopting the abovementioned unit cells,four different multi-band reflective MSs generating multi-vortex beams are designed in three dimensions: frequency,polarization,and mode.The first reflective MS realizes dual-band operation by loading the FSS.Meanwhile,combining the spin-decoupled strategy,the reflective MS illuminated by the CP feed sources could generate four independent transmitting CP vortex beams at Kuand Ka-bands.Besides,the reflective MS illuminated by the linear polarization(LP)feed sources could generate eight correlated LP vortex beams at Ku-and Ka-bands.The second reflective MS introduces the design strategy of regulating multi-polarizations independently,which solves the problem of the first reflective MS being unable to regulate the mode and beam direction of the LP and CP vortex beams independently.Finally,at the Ku-and Kaband,the second reflective MS realizes the independent regulation of the x-polarization,ypolarization,and dual CPs vortex beams.The third reflective MS introduces the method of regulating the high-order Bessel beam,which utilizes the characteristics of the high-order Bessel beam with orbital angular momentum and non-diffraction propagation,thereby solving the divergence problem of the vortex beam in the propagation process.Finally,two CP / four multi-polarization Bessel vortex beams are controlled at K / Ka-band independently,and all the Bessel vortex beams can achieve beam convergence in the near-field area.The fourth MS utilizes the above unit cells operating at three bands and combines the spindecoupled strategy,thereby six independent transmitting CP vortex beams with modes of +1and-1 / +2 and-2 / +1 and +2 are generated at C-/ K-/ Ka-bands,respectively.3.Research of the spliced transmissive MS generating multiple vortex beams simultaneously and independently.By carefully optimizing the radius of the array source and the distance between the MS and the array source,each MS generates the deflection vortex beam with a low side-lobe level and little diffraction.Meanwhile,four transmissive MSs with polarization isolation characteristics are elaborately spliced so that each MS is only excited by the respective antenna array source while showing the polarization isolation characteristic towards the adjacent antenna array sources.Finally,the spliced transmissive MS could generate multiple LP vortex beams with different modes simultaneously and independently in different directions.In addition,the proposed spliced transmissive MS structure could be utilized to splice more transmissive MSs to generate more vortex beams.4.Research of the highly integrating multifunctional transmission-reflection(TR)coding reconfigurable MS in full space.By controlling the states of horizontal / vertical PIN diodes,the TR states of x / y polarizations are regulated dynamically.Meanwhile,adjusting the TR unit phase in horizontal / vertical directions,thereby realizing the independent phase control of the TR x / y polarization.Subsequently,based on the above independent control of different polarizations,two types of MS are designed: The first TR MS could realize multifunctional regulation.Specifically,the transmitted x / y polarized waves realize dual beam deflection / electromagnetic energy focusing,and the reflected x / y polarized waves generate vortex beams with modes of +1 /-1,respectively.The second TR MS could realize phase coding,TR amplitude coding,and beam scanning.Specifically,the x / y polarized incident waves are deflected at 0° / 10° in the transmission state and 165° / 195° in the reflection state,respectively,which corresponds to the phase coding.These above four beams could be switched flexibly in full space,which corresponds to the TR amplitude coding.Moving the position of the feed source realizes the beam-scanning for both x and y polarizations in full space.