Research On Vortex Wave Reflectarray Antenna Based On Metasurface

Vortex electromagnetic waves carrying orbital angular momentum(OAM)are considered as a new method to solve the spectrum resource constraint and increase the channel capacity,and thus become an important research element.Electromagnetic supersurfaces can generate OAM vortex waves efficiently due to their advantages of easy processing and flexible modulation of electromagnetic waves.In this thesis,the design method of vortex wave reflectarray antenna is investigated for different application requirements using electromagnetic super-surface as a research tool,and the main research contents are as follows:In this thesis,several metasurface based vortex wave reflectarray antennas are designed for different application requirements.(1)A resonant metasurface unit with a reflection phase shift of 360° and insensitivity to the incident angle is designed,and the metasurface structure is based on this unit.The convergent phase compensation term is introduced in the calculation of the vortex wave compensation phase,and a convergent vortex wave reflectarray antenna operating at 26 GHz is designed.The simulation results show that the reflectarray antenna generates convergent vortex waves with field enhancement effect.(2)The Bessel phase compensation term is obtained by analyzing the Bessel vortex wave and introduced into the calculation of the reflected surface compensation phase to design a reflectarray antenna with a feed bias of 15° and operating at 26 GHz non-diffraction vortex wave.The simulation results show that the reflectarray antenna generates a second-order non-diffraction vortex wave with pure mode.(3)In this thesis,the phase compensation required for a zero-order Bessel beam radiating in any direction is analyzed,and the spiral compensation phase in the propagation direction is obtained by coordinate transformation,and then the calculation method of the compensation phase for a higher-order non-diffraction vortex wave radiating in any direction is obtained.The simulation results show that the designed reflectarray antenna generates a secondorder non-diffraction vortex wave propagating along θ=30°,φ=0° direction.During the calculation of the compensated phase,the metasurface structure is designed to generate multiple high-order non-diffraction beams in combination with the superposition principle of electromagnetic fields,and the simulation results show that high-order non-diffraction vortex waves with first-order and second-order OAM modes propagating along θ=30°,φ=0° andθ=30°,φ=180° directions,respectively,are generated above the reflection array,which verifies the feasibility of the method.By analyzing the relationship between the reflection coefficients of the metasurface unit by Jones matrix,the structural properties of the metasurface unit based on the geometric phase principle are obtained,and a metasurface unit is designed for broadband application scenarios.Simulation results show that a high-order non-diffraction vortex wave with OAM mode of-2 order is generated in the broadband range of 26 GHz to 31 GHz,which verifies the feasibility of the method.This thesis provides design methods for the generation of vortex waves based on metasurfaces in different application scenarios,which has certain reference value.