Research And Applications Of Novel Metasurfaces With Simultaneous Control Of Amplitude And Phase

Metasurfaces are planar artificial materials and are composed of an array of subwavelength scatterers distributed on a two-dimensional plane periodically.With advantages of manipulating electromagnetic waves flexibly,low profile,less loss,low cost,flexible to design and easy to fabricate,metasurfaces have received widespread attention.Based on the study of novel metasurfaces with simultaneous control of phase and amplitude,this dissertation is aiming at the applications of microwave multi-order diffraction gratings,microwave holography imaging,electromagnetic vortex wave with orbital angular momentum(OAM),Bessel vortex wave and full-space vortex wave,etc.The main contents and innovations are illustrated as follows:Firstly,a novel unit cell which could modulate amplitude and phase independently are proposed.In a wide bandwidth range,the unit can modulate reflected or transmitted electromagnetic waves,and has the advantages of high reflection or transmission rate,good bandwidth performance,independent modulation of amplitude and phase,and 90° linear polarization rotation.The unit is composed of two orthogonal linear polarization grids and a double split ring.The amplitude and phase of the electromagnetic wave can be controlled separately by adjusting the size and rotation angle.Secondly,reflected and transmitted multi-order metasurface gratings are designed.We designed one reflected and two transmitted wideband multi-order diffraction gratings,demonstrating that the unit cell could completely modulate reflected or transmitted electromagnetic waves.Thirdly,a microwave holographic imaging method is proposed.Based on the Rayleigh diffraction theory and the proposed unit's powerful ability which modulate the amplitude and phase of the transmitted electromagnetic wave,three metasurfaces are designed.Fed by the standard horn,the three transmitted metasurfaces will reproduce simple letters,complex portrait,and a high resolution school badge respectively in the specified position.Finally,the generation technology of orbital angular momentum(OAM)vortex electromagnetic wave,Bessel vortex electromagnetic wave with non-diffractive characteristics and full-space vortex electromagnetic wave are studied.Orbital angular momentum vortex electromagnetic wave can improve the channel capacity greatly.We studied the generation technology of vortex electromagnetic waves and analyzed the propagation characteristics of vortex electromagnetic waves.However,the propagation distance of the vortex electromagnetic wave are limited due to its diffraction characteristics,so we use the metasurface which could modulate amplitude and phase independently to produce a non-diffractive Bessel vortex beam.Finally,we proposed a new method to generate full-space vortex electromagnetic waves,which could generates a reflected vortex beam and a transmitted vortex beam simultaneously by one metasurface.