| The antenna of holographic impedance surface that integrates the theory of holographic interference with the modulation principium of the artificial impedance surface,is mainly composed of a source antenna and a holographic impedance modulation surface.Because this type of antenna is usually printed on a circuit board,the source antenna and the holographic structure are printed on the same plane,with a low profile structure,which makes it easy to conform to the carrier and has a good concealment.Moreover,since the antenna feed is generally one or a few,the design of the feed network is relatively simple,with a small loss and a high gain.And the complexity of the antenna system is also greatly reduced.In addition,the holographic antenna can use surface waves to improve antenna performance.Therefore,the holographic impedance surface antenna has the advantages of low profile,high gain,easy conformal,simple feed,flexible polarization,which makes it can be used in military and civil fields as a new choice.This thesis focuses on the design idea of holographic impedance modulation surface.Firstly,the principle of modulation of holographic impedance was analyzed,and the extraction of surface impedance was completed.then,the thesis describes the radiation characteristics of the traditional scalar holographic impedance surface antenna.It is found that in the operating frequency band of the antenna,there is a small cross-polarized component in the TM mode surface wave,and the radiant intensity E_?and E_?of the antenna appear zero-deep in the target radiation direction.Thus,we propose a novel method to construct planar scalar holographic impedance surface structure,which uses two-phase,four-phase,eight-phase,and twelve-phase phase modulation technique to modify the holographic impedance surface.This controls the amplitude of the cross-polarization component and allows this type of antenna to have an ideal all-polarized beam in the operating band and a high gain.Finally,in order to make the antenna conformal to the complex cylindrical carrier,we conduct the conformal processing of two-dimensional plane-to-three-dimensional surface about the surface impedance modulation method on the basis of the above inference.The expressions of the surface wave and the radiated wave in the impedance modulation formula on the corresponding curved surface are presented,and a holographic impedance surface antenna conformal to the cylinder is designed.In addition,in order to obtain a beam in any given direction in space,we study the holographic impedance surface antenna with a spatially-directed beam direction,give a detailed theoretical derivation,and apply it to the design of a conformal antenna. |
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