Theory And Methods For Generating And Receiving Of Electromagnetic Vortex Waves

Orbital angular momentum(OAM)is one of the basic physical properties of electromag-netic waves,and the electromagnetic waves carrying orbital angular momentum is named as electromagnetic vortex waves.Electromagnetic waves have become an important carrier for modern wireless communication technology to carry and transmit information.While with the development of wireless communication technology,people's use of electromagnetic wave spectrum resources has become increasingly tense.The OAM of the electromagnetic vortex wave brings another independent dimension of electromagnetic wave in addition to frequency and polarization.By using this new physical dimension of electromagnetic vortex waves for multiplexed transmission or code modulation of information in wireless commu-nication,it brings hope to the realization of large-capacity and high-rate wireless communi-cation requirements.At present,the application of electromagnetic vortex waves in wireless communication systems is mainly achieved through corresponding transceiver antenna sys-tems.Therefore,the research on the generation and reception of electromagnetic vortex waves is of great significance to realize the application of electromagnetic vortex waves in wireless communication systems.This dissertation studies the theory and methods for gen-erating and receiving of electromagnetic vortex waves,mainly including the following five aspects:1.Aiming at the problem of high side-lobe of the single OAM mode electromagnetic vortex beam generated by the uniform circular array(UCA)antenna,we propose a design scheme of a multi-ring uniform circular array.By improving the calculation method of the array fac-tor of the multi-ring uniform circular array and introducing an optimization algorithm,the appropriate parameters of the radius of the multi-ring uniform circular array are calculated,and the low side-lobe OAM vortex beam design is realized.Compared with the conventional single-ring uniform circular array design,the side-lobe level of our proposed design scheme is reduced by about 6-7 d B.2.In view of the limitation of the space sampling phase aperture interval in the traditional phase gradient reception method for traditional single OAM mode electromagnetic vortex wave,we first establish the Fourier transform relationship between the OAM mode domain and the spatial azimuth domain of the electromagnetic vortex wave.Then through the scale transformation relationship between the OAM mode domain and the sampling aperture az-imuth domain,the extended aperture sampling receiving(EASR)theory and method that are mainly applied to high-order OAM mode receiving measurement is proposed,which breaks through the traditional phase gradient method's limitation of the space sampling phase aper-ture interval.This theory also improves the gradient sampling reception theory,making it complete.3.In view of the limitation that the current partial aperture sampling reception(PASR)meth-ods can only be used to transmit and receive vortex beams with specific OAM mode intervals,we first establish a unified description method of OAM vortex beam aperture sampling re-ception(ASR)theory based on Fourier transform theory and sampling theorem.Then,by circularly adjusting the sampling data received by the partial sampling aperture and its cor-responding sampling aperture scale,a variable scale aperture sampling reception(VSASR)method for hybrid OAM modes vortex beam reception is proposed.This method breaks the limitation of the current partial aperture sampling reception(PASR)method that can only be used to transmit and receive vortex beams with a specific OAM mode interval,and it realizes the reception and separation of the vortex beams with different adjacent OAM modes.4.In view of the beam divergence problem of the OAM electromagnetic vortex beam,we consider combining the design of the Bessel quasi non-diffracting beam and the design of the traditional OAM vortex beam.Then,we propose a hybrid OAM modes Bessel-OAM elec-tromagnetic vortex beam generation design method based on reflective metasurface.This design realizes the quasi-diffraction-free transmission of the mixed-mode OAM electromag-netic vortex beam within a certain range in the near-field region,and it suppresses and im-proves the beam divergence problem of the vortex beam to a certain extent.5.Aiming at the problem of multiple OAM modes multiplexing of electromagnetic vortex waves,we propose a design method for multiple hybrid OAM modes electromagnetic vortex beams multiplexing generation through the multi-feed shared-aperture reflective metasurface technology.We have realized the design of dual-feed dual OAM modes multiplexing gen-eration and four-feed four OAM modes multiplexing generation design respectively.This method provides an important solution for realizing the shared-aperture multiplexing design of multiple OAM modes electromagnetic vortex beams based on metasurface antennas.In summary,based on the basic theories,basic beam characteristics,and basic reception methods of electromagnetic vortex waves,we have carried out researches from these two aspects,the generation and manipulation of electromagnetic vortex waves,and the aperture sampling reception of electromagnetic vortex waves.It provides new research ideas and solutions for the generation and reception of electromagnetic vortex waves,and lays the foundation for its future applications in wireless communication systems.