A miniaturized planar nonbianisotropic left‐handed metamaterial

In this article, a miniaturized nonbianisotropic left‐handed metamaterial composed of spiral‐S‐shaped resonator and conducting wire is proposed. This symmetrical structure avoids bianisotropy and it shows a controllable low‐loss double negative (DNG) band. Its electrical size is less than half of the well‐known S‐shaped resonator, which makes it to be considered as a good homogenous effective media. Although the structure is not uniplanar, it is not vulnerable to fabrication errors stem from misalignment of both sides. Both the simulation and experiment results demonstrate left‐handed properties. Also, a circuit model is proposed which can accurately predict the magnetic resonant frequency. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

A new nonexpandable surface mapping for the design of spherically conformal metamaterial absorbers

The direct design of metamaterial absorbers for the nonplanar surface is cumbersome and inefficient. A new mapping between nonexpandable surfaces and plane structures is proposed, in which the size of geometry on the unit is scaled to avoid the overlap after the mapping. Utilizing this mapping, it is easy to realize the metamaterial absorbers for nonexpandable surfaces, such as the spherical surface, while maintaining or even getting better performance by adopting the genetic algorithm combined with the load‐resistors matrix decomposition method. A prototype has been fabricated by 3D printing technology to precisely locate the units on the spherical crown. The simulation and experimental results show that the designed structure has broadband absorbing bandwidth in the 2.7 to 8.2 GHz for 10 dB radar cross‐section reduction under the normal incidence. This prototype also has good polarization and incident angle stability.     

Miniaturized resonant inclusions as non-bianisotropic double negative metamaterials for normal incidence

Two novel resonators were devised which are amendments on commonly used S-shaped resonator and enable a great miniaturization rate. The symmetrical structure of these inclusions can avoid magnetoelectric coupling in the artificial constituents that preclude the bianisotropy. One of these metamaterials is an integration of continuous wire and an S-shaped-spiral. The other is a structure of SRRs and S-shape resonator with improved electromagnetic coupling and reduced electrical size. Both of them have wide negative refraction passband with low losses. The superior performances of these structures were investigated numerically and experimentally for only normal incidence case and tested through a proper comparison with the S-shaped resonator.     

应用超常介质设计柱形隐形容器

超常介质是一种纳米尺度的人工复合材料,可以同时设定材料的介电常数和磁导率。利用超常介质的这一特性,能够自由地调整光的传播路径。在此基础上,应用坐标转换的方法,计算出圆柱形和椭圆柱形的介电常数和磁导率分布,让光在介质内沿着特定的轨迹传播,绕过包围的空腔,沿入射的方向出射,从而实现圆柱和椭圆柱形状的隐形。     

Fabrication of Metamaterials Based on Gold Dendritic Cells

介绍了一种由无序树形结构构成的超材料的自下而上化学制备方法,这种超材料可工作在可见光频段。当树形结构的直径为500 nm时,这种金纳米树形结构阵列超材料分别在470,540,670 nm频段出现透射通带,这种超材料也可在可见光频段实现平板聚焦,有益于对可见光频段超材料的研究     

一种单面双L型异向介质的设计及分析

针对目前已有的异向介质带宽窄,结构复杂的缺点,设计了一种工作在Ku波段的单面双L型异向介质结构。通过采用电磁仿真方法,建立平面电磁波垂直入射异向介质平板的模型,并提取其传输和反射数据;借助MATLAB工具,根据NRW（Niconlson－Ross－Weir）方法从中提取出该新型结构的等效介电常数和等效磁导率。仿真结果表明,这种单面双"L"型的结构在频段为14．2~15．9 GHz的等效介电常数与等效磁导率同时为负,其有效绝对带宽1．9 GHz;在11~17 GHz频段内的有效相对带宽为31．7%。因为这种异向介质结构在特定工作频率下电磁参数同时为负值,并且通过计算频率为15 GHz时的电磁波的相速为－2×107 m/s,验证了该异向介质的结构具有后向波特性。这种结构具有便于制造及可控两大优势,具有很大的应用前景。     

基于超材料的双频微带天线RCS减缩研究

针对双频微带天线的带内雷达散射截面减缩问题,提出了一种加载型微带天线。通过在贴片周围加载吸波超材料,天线的带内雷达散射截面得到有效减缩。该超材料吸波体仅由两层金属及其中间的有耗介质组成,底面金属不刻蚀,顶面由双环方形贴片组成。仿真结果表明:当天线周围加载吸波材料后,在保持天线辐射性能基本不变的情况下,双频带的雷达散射截面分别获得8.0d B和5.5d B的减缩。     

应用于WiFi/WiMAX的三频超介质加载天线

以研究超介质结构在天线中的应用为目的,采用了超介质理论中的负折射率传输线(NRI-TL)加载技术,设计了一种三工作频段的单极子贴片天线.该单极子天线由不均匀弯折线构成,采用共面波导(CPW)馈电.在2.45 GHz和55 GHz附近弯折线与超介质结构可形成折合单极子辐射;在3.55 GHz附近超介质结构可改变天线表面电...     

Large gradients of refractive index in nanosphere dispersed liquid crystal metamaterial with inhomogeneous anchoring: Monte Carlo study

We study the effect of spatial inhomogeneity of anchoring forces on real part of effective refractive index in nanosphere dispersed liquid crystal (NDLC) metamaterial at infrared frequencies using the approach of Khoo et al. [1] and Monte Carlo modeling proposed recently in Ref. [2]. Local and global characterization is made using 2D maps of spatial distribution of the index, its gradients and its modulation amplitude below and above Freedericksz threshold. We find that NDLC with step-wise modulation of anchoring forces gives rise to much larger gradients and absolute values of the effective index than NDLC with modulated external electric field as well as pure nematic liquid crystal (NLC) with inhomogeneous anchoring. This indicates that the filling factor of coated spheres in NDLC is an important design parameter which tunes the effective refractive index. We find that the results are strongly dependent on wavelength in the infrared interval 2800-2900 nm. Some potential applications to molding the flow of light are briefly mentioned.