| Vortex electromagnetic wave has become a research hotspot in the field of wireless communication in recent two years because it provides new degrees of freedom in the topological charge domain.The twisted structure of Vortex electromagnetic wave has orbital angular momentum(OAM).Accordingly,Vortex electromagnetic wave can realize azimuth high resolution imaging by using the dual relationship between the topological charge variable and the azimuth variable.The key problem of vortex electromagnetic wave imaging is that the antenna pattern does not meet the imaging requirements.In order to realize the imaging of vortex electromagnetic wave,the transmitting antenna of vortex electromagnetic wave must be able to generate vortex electromagnetic wave with arbitrary topological charges.At present,concentric ring array is used as transmitting and receiving array antenna,which can generate vortex electromagnetic waves and is technically easy to control the antenna pattern.Traditional array antenna pattern synthesis methods,such as Taylor synthesis method and Bayliss synthesis method,are all aimed at plane electromagnetic wave,but not at vortex electromagnetic wave.Therefore,it is necessary to carry out the research on array antenna pattern synthesis of vortex electromagnetic wave imaging to solve the key technical problems of transmitting and receiving vortex electromagnetic wave in vortex electromagnetic wave imaging,so as to provide theoretical support and design guidance for the experimental study of eddy electromagnetic wave imaging.In order to obtain higher resolution of electromagnetic imaging and solve the technical problem of generating arbitrary topological charges electromagnetic wave in vortex electromagnetic wave imaging,this paper establishes the radiation mathematical model of concentric circular array antenna by studying the radiation pattern of concentric circular array antenna,and puts forward a pattern synthesis method that meets the requirements of vortex electromagnetic wave imaging,so as to provide theoretical support for concentric circular array antenna design.At present,the reported array antenna is still a relatively simple circular array,which has some defects,such as high sidelobe level,uncontrollable sidelobe and too large divergence angle.In this paper,several concentric circular array antennas are used to control the amplitude and phase of each antenna element.An algorithm is proposed to synthesize the low sidelobe level,controllable radiation direction and vortex electromagnetic wave pattern which can generate arbitrary topological charges.Finally,the feasibility of OAM imaging of integrated array antenna is verified by theoretical analysis and numerical simulation of one-dimensional imaging in azimuth direction,range direction and azimuth direction of votex electromagnetic wave,which provides theoretical support for its application in radar target imaging and other fields.The main work and innovation of this paper are as follows:(1)An antenna pattern synthesis method is proposed,which can simultaneously generate vortex electromagnetic waves with multiple topological charges.(2)Theoretical study of the one-dimensional and two-dimensional imaging based on vortex electromagnetic wave. |
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