Research And Application On Some Topics Of Polarization And Angular Momentum Of Electromagnetic Wave

Polarization and angular momentum of electromagnetic(EM)wave play a significant role in EM research.The manipulation of EM polarization is one of the key issues in various studies on EM polarization.The improvement of metamaterial benefits the design of polarization manipulation devices a lot.The research on EM angular momentum,particularly on orbital angular momentum(OAM),becomes a hot topic due to its potential application in communication technology.By being employed in massage transmission or multiplex technique,it can boost the data communication rate,which provide a new chance for development of communication.Focusing on the topics of EM polarization,the polarization manipulation in microwave band is studied and realized in this dissertation.It is subsequently applied in selective wave-transmitting absorber(SWTA)design.Polarization manipulation is achieved by employing Huygens' principle.A device which can transform a linear polarized incident wave into one with multiple polarizations is designed through analyzing Pancharatnam-Berry(P-B)phase of a linear-polarized EM wave and characteristic modes of a perturbation on loaded patch structure.A SWTA metasurface is achieved by combining a transmissive polarization convertor and a polarizationdependent absorber.On the topics of EM angular momentum,some studies of OAM generation,reception and multiple-modes working in microwave band is performed.After comparing spin angular momentum(SAM)and OAM,the intermediate forms between SAM and OAM are derived and further applied in some research of EM wave.To summarize,the main contributions of this dissertation are listed below:(1)An approach based on Huygens' principle is introduced in polarization manipulation through inducing coupling between equivalent electric and magnetic sources in the metamaterial.A polarization conversion splitter as well as reflective and transmissive polarization convertors are designed on the basis of this method.The proposed polarization manipulation devices possess compact unit-cell size in the deep sub-wavelength regime and maintain good oblique incident performance.Then,a polarization convertor which can transform a linear-polarized EM incident wave into co-,cross-,left hand and right hand circular-polarized outgoing waves at different frequency is designed.Its phase control is based on P-B phase of linear-polarized EM wave,meanwhile,the magnitude is based on characteristic mode analysis(CMA)of microstrip structure.(2)The polarization manipulation is applied in frequency selective metamaterial absorber design.Firstly,absorbers with unit-cell of parallel and series effective circuit as well as one based on effective electric-magnetic sources are realized after studying absorber's design method.A SWTA is achieved by transforming selection of frequency to selection of polarization.To verify the design method,a composite metasurface composed of a transmissive polarization convertor and a polarization-dependent absorber is design.Finally,on this topic,a selective wave-reflecting absorber(SWRA)and a selective wave-reflecting/transmitting absorber(SWRTA)are designed and simulated by equivalent circuit analysis.(3)Researech on angular momentum is started from the calculation of OAM and SAM.The phased-approach for OAM generation is studied after investigating the phase distribution of the OAM,which is then realized by employing an annular antenna array,a rectangular antenna array,or a metasurface.The amplitude-controlled-approach is also proposed and verified by employing an amplitude-weighted array,which shows the relationship between OAM and magnitude distribution.(4)Based on phased-array theory,we use an annular phased array to realize the beam scanning of OAM wave.The OAM generation device with multiple beam/mode/polarization cabability are design by employing an anisotropy metasurface or a multi-polarized antenna array.Non-circularly polarized OAM wave is achieved by nonlinear phase setting of an annular array,which can benefit the recieving of OAM wave.(5)By comparing the characteristics of SAM and OAM,we propose intermediate forms between them which can be used to correlate them simply,and describe their rotational phase explicitly in the mathematical expressions.According to this method,SAM-OAM coupling(SOC),pseudo wave vector of OAM wave,circularly polarized beam steering antenna array,frequency scanning antenna array,ultra-wideband phase shift,rotation phase of OAM and rotational Doppler effect of angular momentum are discussed,respectively.