| In recent years,with the rapid development of long-distance wireless communication systems,antennas with reconfigurable working states have attracted extensive attention from researchers at home and abroad.From left-handed medium to digital coding metamaterials,the emergence and development of artificial electromagnetic materials have brought inspiration and new solutions to antenna design.In this thesis,while designing a pattern reconfigurable antenna,digital coding metamaterials are used to realize the functions of low sidelobe,low antenna profile and radar cross-section(RCS)reduction.Based on low cost,light weight,and simple structure,the adaptability of the reconfigurable antenna is also enhanced.The main research contents of this thesis are as follows:1.A 1-bit reconfigurable transmission array antenna with low sidelobe characteristics is proposed.Firstly,a 1-bit circularly polarized metamaterial element with adjustable initial transmission phases is constructed.Combined with the particle swarm optimization(PSO)algorithm,the initial phase of each element and the coding distribution on the aperture surface under different scanning angles are optimized.It has good two-dimensional beam scanning ability at 9.5GHz with 8.4% relative impedance bandwidth.For the main beam of 0° scanning angle,the peak gain is 16.5d Bi,the maximum aperture efficiency is 21%,the relative 3d B gain bandwidth is 17.6%,and the relative 3d B axis ratio bandwidth is5.2%.2.A 1-bit reconfigurable folded transmission array antenna with low profile characteristics is proposed.Firstly,a microstrip patch feed and a polarization conversion metasurface are designed.Combined with the 1-bit metamaterial element designed in Chapter 2,a1-bit reconfigurable folded transmission array antenna is composed.With the aid of PSO algorithm,the initial phase of each element and the code distribution on the aperture surface under different scanning angles are optimized.It has good two-dimensional beam scanning ability at 9.5GHz with 7.4% relative impedance bandwidth.For the main beam of 0° scanning angle,the peak gain of the antenna at 9.5GHz is 19.3d Bi and the aperture efficiency is about 20.5%.The relative 3d B gain bandwidth of the antenna is 9.4%,and the relative 3d B axial ratio bandwidth is 16%.3.A 1-bit reconfigurable transmission array antenna with low RCS is proposed.Firstly,a1-bit metamaterial element with independent reconfigurable transmission mode and reflection mode is designed.By controlling the working state of PIN diode,the 1-bit transmission phase difference for x-polarized wave and the reflection phase difference of110° ～ 230° for y-polarized wave can be realized independently in the range of 9.2GHz to 10.2GHz.With the calculation of the coding distribution under different scanning angles,the antenna has good two-dimensional beam scanning ability at 9.7GHz and 9.3%relative impedance bandwidth.For the main beam of 0° scanning angle,the peak gain of the antenna at 9.7GHz is 18.2d Bi,the corresponding aperture efficiency is about 21%,the 3d B gain bandwidth of the antenna is 9.3GHz～10.2GHz,and the relative 3d B gain bandwidth is 9.2%.For the xpolarized wave vertically incident on the aperture surface,the antenna can achieve RCS reduction of more than 5d B from 9.4 GHz to 10.2 GHz;For the y-polarized wave,by controlling the reflection working state of each reconfigurable element,the antenna can realize the reconfiguration of the scattering pattern.In this way,electing different reflection coding sequences can effectively reduce the RCS in different frequency bands,so as to realize flexible RCS reduction. |
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