Metasurface Regulation Characteristics And OAM Simulatioan

Orbital angular momentum(OAM)has infinitely many orthogonal modes,therefore the vortex beam carried OAM can constitute an infinitely multidimensional Hilbert space state.Theoretically,OAM technology can achieve an infinite bandwidth of the communication channel.Theory that OAM is used as a multiplexing freedom different from frequency,amplitude and polarization to realize multiplexing technology has set off a research boom,it has shown great potential in improving the capacity and frequency band utilization of wireless communication systems.All the premise of OAM multiplexing technology and its application is how to effectively generate vortex beams.So far,research on the generation of vortex beams in the optical field has become increasingly mature.However,since the size of optical device is too large and the divergence angle is too wide,it is difficult to apply it all to the wireless communication system in the microwave section.It is urgent to study the generation of vortex beams in the microwave segment.A novel method is to adjust the phase,amplitude and polarization of the incident wave by artificial electromagnetic metasurface to realize vortex beam.This is also the main research work of this paper.The specific research contents are as follows?.Based on the generalized Snell's law,the phase regulation characteristics of the metasurface to the incident wave are analyzed.The Jones matrix is introduced to analyze the amplitude and polarization regulation characteristic of the incident wave.According to structural characteristics of unit cell,it is divided into five categories,and the corresponding transmission characteristics are given?.The general principles and characteristics of OAM are introduced,and the conventional methods of generating OAM are summarized.Combining with the above theory and metasurface control characteristics,a transmissive metasurface based on ?-type unit cell is designed.After studying the effects of polarization conversion characteristics,surface current distribution and geometric parameters unit cell on transmission characteristics,the simulation realizes vortex beam generation of two modes at the single frequency point in the microwave segment,and analyzes the effect of the working frequency on vortex beam generation.?.Combining OAM theory and metasurface regulation characteristics,a reflective broadband metasurface based on S-type unit cell is designed.The research shows that the incident angle and polarization angle of the incident wave have an influence on transmission characteristics of unit cell.The simulation realizes the vortex beam generation of two modes in the microwave segment.?.The reflective metasurface is improved for the case where the actual feed is spherical.A cone horn antenna is designed that operates in a particular frequency band to produce the desired stable spherical wave.The simulation then realizes the vortex beam generation under the incident of spherical wave,and analyzes the influence of the position of the feed on vortex beam.