Research Of Transmission Properties For Electromagnetic Wave Orbital Angular Momentum

With the rapid development of mobile Internet services, wireless spectrum and channel capacity has been increasingly crowded which breeds new technical breakthrough in the communication field. The "state division multiplexing (o)" of electromagnetic wave Orbital Angular Momentum (OAM) is a whole new mechanism. This mechanism comes with hope on increasing the spectrum efficiency and fulfilling the greater transmission capacity of bearing the same frequency band from a new dimension.First of all, the researching significance and current status of OAM is introduced in this thesis, then the basic principles of OAM and the way how to raise it is expounded. And succeeded by that, micro-strip array antenna and dipole array antenna to produce electromagnetic wave orbital angular momentum are analyzed in detail. Theoretical analysis and numerical simulation results show that the far field of antenna arise radiation hole and the hole size augments gradually when OAM mode order and the propagation distance increase. Also, the increase of the propagation distance, radius of antenna array and OAM mode order will induce pattern fuzzy, and deteriorate resolution of the OAM mode, all these will affect the information coding of the wireless communication.Aiming at these problems, parabolic reflection structure is added to dipole antenna array, then the physical optics method, the Fourier-Bessel method and the improved Fourier-Bessel method are applied for calculation. The consistency of results of these calculations demonstrates the effectiveness of such an approach and also proves that the improved Fourier-Bessel method can effectively enhance the computation efficiency. Moreover, simulated results show that the added parabolic reflection structure solves the defect of radiation zero when the OAM propagates to some extent, this structure can produce multiple state of the OAM wave at the same time, maintaining the electromagnetic characteristic of the OAM. Technical route of this thesis is feasible, and the state division multiplexing theoretical basis is provided for application in the field of wireless communications.