散射参数法在二维超表面电磁均一化中的应用

发布时间：2018-12-16 02:53

【摘要】：随着信息技术的发展,单个移动终端设备中集成的无线通信方式越来越多,如Wi-Fi,GPS,NFC,蜂窝网通信,蓝牙等等,这就要求天线能够在多个频段工作。使天线多频工作的方法很多,本文以二维结构的超表面来设计频率可重构的天线,并以此来探讨二维结构的超表面电磁均一化的相关问题。超材料是由人工设计的一些特殊结构所构成的新型材料,它具有自然界中存在的天然材料所不具备的特殊的物理特性。二维结构的超表面是将三维的超材料制成平面结构而得到的,与三维超材料相比,它具有体积小、重量轻的优点。将人工设计特定的单元结构进行周期或者非周期的重复而成的超表面,具有特殊的电磁特性,加载在天线上可以天线的工作频率,极化和方向图进行控制。本文通过设计一个工作在C波段的微带缝隙天线作为辐射天线,并设计了线状、长轴短轴比为10的椭圆状、长轴短轴比为3的椭圆状和圆状这四种不同单元结构且能够实现天线工作频率可重构的超表面。将超表面直接加载在微带缝隙天线上,通过旋转超表面,改变天线与超表面的相对位置来实现微带缝隙天线工作的重构。利用CST微波工作室对所建的超表面加载天线进行仿真,可以得出四种结构基于超表面频率可重构天线的频率可重构范围。线状、长轴短轴比为10的椭圆状、长轴短轴比为3的椭圆状和圆状结构的超表面的频率可重构范围分别为958MHz、808MHz、660MHz和96MHz。本次设计选择了长轴短轴比为3椭圆状的超表面,微带缝隙天线和线结构的超表面进行加工并在微波暗室进行测试,仿真与测试结果较好的吻合。通过旋转超表面能够实现天线工作频率变化的原因是,改变超表面与天线的相对位置改变了超表面的等效介电常数和等效磁导率。对超表面进行电磁均一化可使用散射参数逆推法(NRW)进行计算。首先,通过对超表面的单元结构进行电磁仿真,得出单元结构的散射参数,然后再应用NRW算法,对所得的单元的S11和S21逆向推导出等效介电常数和等效磁导率,最后用这些等效电磁常数分别建立四种结构的超表面等效介质模型并加载在天线上进行仿真,将得到的结果与实际的超表面加载天线的仿真结果对比,超表面的等效介质模型仿真结果与实际模型仿真结果匹配。
[Abstract]:With the development of information technology, there are more and more integrated wireless communication methods in single mobile terminal devices, such as Wi-Fi,GPS,NFC, cellular network communication, Bluetooth and so on, which requires antennas to work in multiple frequency bands. There are many methods for multi-frequency antenna operation. In this paper, the frequency reconfigurable antenna is designed with the supersurface of the two-dimensional structure, and the related problems of electromagnetic homogenization of the supersurface of the two-dimensional structure are discussed. Metamaterial is a new type of material which is composed of some special structures designed by man. It has special physical properties which are not possessed by natural materials existing in nature. The supersurface of two-dimensional structure is made into planar structure of three-dimensional metamaterials. Compared with three-dimensional metamaterials, it has the advantages of small volume and light weight. The supersurface, which is composed of periodic or aperiodic repeated elements, has special electromagnetic characteristics. The frequency, polarization and pattern of the antenna can be controlled by loading it on the antenna. In this paper, a microstrip slot antenna working in C-band is designed as a radiation antenna, and an ellipsoid with a linear, long axis / short axis ratio of 10 is designed. The ellipsoid and circular structure with long axis and short axis ratio of 3 are four different elements and can realize the reconfigurable supersurface of antenna working frequency. The supersurface is directly loaded on the microstrip slot antenna and the working reconstruction of the microstrip slot antenna is realized by rotating the supersurface and changing the relative position between the antenna and the super-surface. The CST microwave studio is used to simulate the supersurface loaded antenna, and the frequency reconfigurable range of the four structures based on the super-surface frequency reconfigurable antenna can be obtained. The frequency reconfigurable ranges of ellipsoid and circular structure with linear, long axis short axis ratio 10 and long axis short axis ratio 3 are 958 MHz / 808 MHz and 96 MHz, respectively. In this design, the supersurface with the long axis and short axis ratio of 3 ellipsoid, the microstrip slot antenna and the supersurface of the wire structure are fabricated and tested in the microwave darkroom. The simulation results are in good agreement with the test results. The reason why the antenna operating frequency can be changed by rotating the supersurface is that the relative position between the supersurface and the antenna changes the equivalent permittivity and permeability of the supersurface. The electromagnetic homogenization of the supersurface can be calculated by using the backstepping method of scattering parameters (NRW). First, the scattering parameters of the supersurface element structure are obtained by electromagnetic simulation, then the equivalent permittivity and the equivalent permeability of the element S11 and S21 are derived by using the NRW algorithm. Finally, the supersurface equivalent dielectric models of four structures are established by using these equivalent electromagnetic constants and simulated on the antenna. The results obtained are compared with the simulation results of the actual supersurface loaded antennas. The simulation results of the supersurface equivalent medium model match the simulation results of the actual model.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB34;TN820;O441

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