| Orbital angular momentum(OAM)is an important basic physical property of electromagnetic waves,and electromagnetic waves carrying orbital angular momentum are generally called vortex electromagnetic waves.With the rapid development of wireless communication technology,expanding the channel capacity of wireless communication has become the main means to solve the shortage of spectrum resources.The orbital angular momentum in the vortex electromagnetic wave provides another independent dimension in addition to the frequency,magnitude,phase,and polarization of the electromagnetic wave.Applying it to the spatial multiplexing transmission in wireless communication can provide a feasible solution for high-speed wireless communication.Therefore,it is of great significance to use orbital angular momentum multiplexing to improve the utilization of spectral resources and to study the characteristics of vortex electromagnetic waves and their application in practical processes.In this thesis,the design of the array antenna generated by the vortex electromagnetic wave is studied.The vortex electromagnetic wave’s robust antijamming characteristics and long-distance communication performance are analyzed.The main work of this thesis is divided into the following three points:1.Design of a multi-mode hybrid vortex electromagnetic wave double-loop concentric circular array antenna.Aiming at the problems of excessively large array size and complex feeding design when traditional annular arrays generate vortex electromagnetic waves,this thesis proposes a uniform circular array design scheme with multi-ring concentric circles nesting.The antenna array is fed alternately in groups to generate multiple modes of vortex beams.In addition,a centrally fed circularly polarized antenna array element is designed to simplify the feeding design of the array.Finally,according to the characteristics of the crosspolarization of the pattern,the axial ratio performance of the vortex beam is optimized by adjusting the rotation angle of the initial array element of each vortex mode.The designed antenna array can realize the transmission and reception of vortex electromagnetic waves with four modes mixed based on reducing the size of the array,and the resulting mixedmode vortex beam has high modal isolation and good axial ratio performance.2.Design of angle-cut square array antenna for low sidelobe deflection vortex electromagnetic wave.This thesis proposes a design scheme of a deflection vortex electromagnetic wave angle-cut square array antenna with a low sidelobe level.First,a deflectable vortex beam is generated by superimposing the vortex and beam deflection phases.The amplitude weighted distribution is combined with the vortex electromagnetic wave generating array antenna.The influence of the amplitude weighted design on the sidelobe level of the vortex electromagnetic wave is analyzed.Finally,the designed antenna array is simplified through amplitude quantization,reducing the feeding design complexity.The proposed vortex beam array antenna chamfering design scheme can generate four OAM modal deflection vortex beams,and the sidelobe level of each modal beam is low.The array scheme can be applied to interactive communication scenarios of multiple devices in space.3.Anti-interference performance analysis of vortex electromagnetic wave and research on superposition mixed-mode vortex beam generation of OAM mode group.In order to analyze the anti-interference performance of vortex electromagnetic waves,this thesis proposes an analysis method of introducing spatial interference sources into the transmission link of vortex electromagnetic waves.The spectral distribution changes with the size of the sampling aperture,which can provide an analysis idea for the anti-interference performance of the vortex beam.In addition,given the divergence problem in the transmission of vortex electromagnetic waves,this thesis proposes a design method of using a multi-loop array antenna to generate a mixed-mode vortex beam with superposition of OAM mode groups.The vortex beam demodulation method with partial aperture sampling is used in the receiving area.This design scheme can solve the problem of energy divergence in the longdistance transmission of vortex electromagnetic waves.In summary,by designing an antenna array that generated mixed-mode and deflected beam vortex electromagnetic waves and exploring the anti-interference characteristics of orbital angular momentum of vortex electromagnetic waves and the superposition characteristics of multiple OAM modal groups,the antenna design and development of vortex electromagnetic waves are discussed.The application method provides a new research idea,which also lays a foundation for the further research and application of vortex electromagnetic waves. |
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