| Holographic impedance surface is a kind of artificial electromagnetic metasurface formed by combining the principle of optical holography and the principle of periodic leak-wave antenna.Antenna designed based on holographic impedance surface has attracted much attention because of its advantages of high gain and low profile.In addition,the conformal design of the antenna can well integrate the antenna and the platform,without affecting the aerodynamic performance of the platform,and can effectively reduce the RCS.Therefore,the research on conformal holographic impedance surface antenna is of great significance.The main research contents of this paper include the following three aspects:1.The impedance characteristics of holographic impedance surface element are studied in depth.Firstly,the eigen mode method to extract the surface impedance of the element is introduced.Then,the influence of the size of the metal patch and slot angle of the tensor element on the equivalent surface impedance of the element is analyzed.Finally,the design process of the antenna is introduced.2.The design method of cylindrical holographic impedance surface antenna to achieve near-field focusing function is proposed.The relationship database between the element size and the equivalent impedance is established,and the design formula of the conformal holographic impedance surface antenna is derived.The simulation and measurement results show that the designed cylindrical holographic impedance surface antenna can effectively achieve focusing in the near-field region.It is expected to replace the traditional phased array antenna,avoid the complex feed network,and achieve near-field focusing,which can provide a reference for the application of cylindrical holographic impedance surface antenna in near-field focusing.3.The design method of cylindrical holographic impedance surface antenna radiating orbital angular momentum(OAM)vortex electromagnetic wave is proposed.A cylindrical holographic impedance surface antenna radiating OAM vortex electromagnetic wave was designed and fabricated by conformal formula.The simulation and measurement results show that the designed cylindrical holographic impedance surface antenna can effectively generate OAM vortex electromagnetic wave with mode number l=+1 at 24 GHz and 24.25 GHz.This can provide reference for OAM communication and radar system in cylindrical conformal devices. |
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