单方环结构左手材料微带天线

设计了一种简单的双面单方环结构左手材料,在4.8–5.25 GHz频率范围内该材料的等效介电常数和等效磁导率同时为负.将此单方环左手材料作为覆盖层,置于中心工作频率为5.0 GHz的微带天线之上. 仿真和实验研究表明:相对普通微带天线而言,覆层微带天线的性能得到了明显改善, E面和H面的半功率波束宽度分别收缩了25°和20°,定向性得到了提高, 5 GHz处的增益提高了3 dB, -10 dB带宽增加了600 MHz. 关键词： 单方环结构 左手材料 微带天线     

等效环路有限差分算法及其在人工复合材料设计中的应用

本文实现了一种新颖的等效环路有限差分算法, 这种算法借鉴传输线算法的思想, 在Yee氏网格中引入等效集总元件, 包括常规介质中的等效串联电感、并联电容和左手材料中的等效并联电感、串联电容等. 良好的物理思想使其可以提供适用色散介质计算的收敛性条件, 更加适合仿真计算频率选择表面和超材料等色散介质. 为了提高其计算效率, 研究了核内加速技术, 这种技术理论上可达到最高4倍的加速, 实际应用中得到2倍左右的加速效果. 使用该算法进行了超材料吸波体结构的设计, 通过单双环电阻加载实现宽带电磁波吸收功能. 隐身天线罩对于实现天线的带外隐身有着重要作用, 利用该算法设计了工作频率为1 GHz, 隐身频带在3 GHz到9 GHz的天线罩. 并与两个加工样品的测量结果进行了比较, 对比的结果验证了算法的正确性. 同时核内加速技术的有效性也通过仿真时间比较得到了验证. 关键词： 等效环路有限差分算法 核内加速 超材料吸波体 隐身天线罩     

交指电容加载的周期性对称负磁导率人工材料研究

利用二端口网络理论和弗洛奎定理, 详细分析了周期性对称磁谐振人工材料的相对布洛赫磁导率与散射矩阵参数的关系, 利用这个关系提取了四种形式的开口谐振环布洛赫磁导率. 全波仿真和磁导率数值提取结果表明, 在开口谐振环的开口处加载交指电容, 磁谐振频率将显著降低. 这些成果将为提取周期性人工材料的布洛赫磁导率提供理论依据, 同时为小型化磁谐振特异人工材料提供新的设计思路.     

基于蘑菇型结构的双入射超宽带复合媒质材料设计与分析

通过设计一定的单元结构, 可以实现超宽带人工电磁材料. 基于蘑菇型金属结构, 提出了一种同时具有左右手通带无缝结合的超宽带双入射型复合媒质材料结构单元. 该结构由嵌入到介质板的两个反向对称的蘑菇型金属结构组成, 能够同时引发电谐振和磁谐振而得到左手通带. 通过利用CST软件仿真、等效电磁参数提取、折射率计算以及建立等效磁谐振电路模型等方法, 分析验证了该结构的双入射特性和左手特性. 仿真结果表明, 在电磁波垂直于介质板和平行于介质板入射两种情况下, 在X波段均表现出左手通带特性, 并具有1 GHz以上的左手带宽. 当电磁波垂直于介质板入射时, 在7.2 GHz-9.3 GHz频段为右手通带, 在9.3 GHz-11 GHz频段为左手通带; 当电磁波平行于介质板入射时, 在7.0 GHz-9.0 GHz频段为右手通带, 在9.0 GHz-10 GHz频段为左手通带. 在两种情况下分别于9.3 GHz与9.0 GHz处得到了零折射率, 从而构造了一种正-零-负复合媒质材料, 实现了具有3 GHz带宽的双入射超宽带平衡结构.     

Design of a small-sized expanded coaxial line antenna at L-band

为了减小常规L波段高功率微波测量接收天线的结构尺寸及增益,设计了一种基于轴向缝隙馈电的小型化同轴扩张型天线.通过理论分析和数值模拟,选择了较优的结构尺寸,得到天线的增益及方向图特性:在1.3～1.6 GHz范围内,增益从-2.0 dBi变化至0.8 dBi；天线最大辐射方向在物理结构轴向.基于矢量网络分析仪E8362B的天线特性测量结果与数值计算结果基本一致:工作频率从1 3～1 6GHz变化时,增益从-2.3 dBi变化至1.2 dBi；E面方向图主瓣宽度大于 60°,轴向轴比大于35dB,结果表明设计的天线能够满足L波段高功率微波渊量天线低增益小型化要求.     

基于多开口田字形宽频带低损耗左手材料

提出了一种基于多开口田字形单元结构实现材料左手特性的设计方案.该结构是在介质基板单侧集成电、磁谐振器形成左手单元.通过理论分析、软件仿真、加工测试、提取有效电磁参数,结果表明该结构在12.7—21.1 GHz范围内具有双负特性(等效介电常数ε0,等效磁导率μ0),基本覆盖Ku波段,绝对带宽可达8.4 GHz,单元损耗低于0.3 d B.同传统的左手材料相比,该结构以更小的单元尺寸,更低的损耗实现了更宽的左手频带,为宽频带、低损耗微波左手材料的设计及广泛应用提供了重要参考.     

基于零折射磁性特异电磁介质的波前调控

本文基于二维磁性柱周期阵列设计了具有等效零折射率的磁性特异电磁介质. 通过多重散射理论计算体系的光子能带和等效介质理论提取体系的等效电磁参量可以确定该磁性特异电磁介质可以实现等效介电常数和等效磁导率同时为零. 利用该双零磁性特异电磁介质可以实现电磁波在无相位延迟下的传输, 从而可以调控电磁波的空间相位变化. 进而, 通过设计具有不同电磁波输出界面的构型实现了高斯光束的波前由平面转变成柱面, 还可以实现高斯光束的聚焦和高斯光束的分束. 也可以根据需要设计具有更为一般的输出界面, 实现更为多样的电磁波波前的调控. 而且, 磁性材料的电磁特性可以通过温度和外加磁场进行调制, 因此该双零磁性特异电磁介质的工作频率可以灵活控制, 这更便于电磁波器件的设计和应用.     

方环结构的宽频可调超材料滤波器

采用微控制电路加载技术控制超材料的等效介电常数和等效磁导率在不同时间的空间分布形式,实现空间滤波器中心频率的可调.设计了一种方环缝隙结构超材料滤波器,单元结构尺寸为18.5mm×18.5mm,通过在单元结构上加载变容二极管实现X波段内的连续可调.当变容二极管电容值从0.15pF增大到0.70pF时,仿真结果表明滤波器的中心频率从11.8GHz逐渐减小到10.5GHz,工作带宽为16.3%(10.2~12.0GHz),通带内的回波损耗最小值为22dB,插入损耗最大值为0.6dB.测试结果表明滤波器的中心频率从11.7GHz逐渐减小到10.3GHz,工作带宽为17.2%(10.1~12.0GHz),且通带内的回波损耗最小值为25dB,插入损耗最大值为0.5dB.     

基于宽边耦合螺旋结构的低频小型化极化不敏感超材料吸波体

设计、仿真并实验验证了基于宽边耦合螺旋结构的低频小型化超材料吸波体. 实验测试结果表明, 该超材料吸波体在1.39 GHz吸收率达到最大为98%, 其单元尺寸和总厚度均为6.8 mm, 约为1/32工作波长, 实现小型化窄带吸波. 由于吸波体中螺旋结构是旋转对称排列的, 因而其对垂直入射电磁波的极化方向是不敏感的. 此外, 该超材料吸波体对斜入射横电和横磁极化电磁波在60°时, 仍具有强吸收. 关键词： 超材料 吸波体 小型化     

L波段小型化同轴扩张型天线设计

为了减小常规L波段高功率微波测量接收天线的结构尺寸及增益,设计了一种基于轴向缝隙馈电的小型化同轴扩张型天线。通过理论分析和数值模拟,选择了较优的结构尺寸,得到天线的增益及方向图特性:在1.3~1.6 GHz范围内,增益从-2.0 dBi变化至0.8 dBi;天线最大辐射方向在物理结构轴向。基于矢量网络分析仪E8362B的天线特性测量结果与数值计算结果基本一致:工作频率从1.3~1.6 GHz变化时,增益从-2.3 dBi变化至1.2 dBi;E面方向图主瓣宽度大于60,轴向轴比大于35 dB,结果表明设计的天线能够满足L波段高功率微波测量天线低增益小型化要求。     

Enhancement of magnetic field intensity with a left-handed metamaterial tunnel resonator for obstacle sensing

A narrow metal strip inspired by the left-handed metamaterial and sensitive LC resonator structure has been released in this work where the narrow metal strip is presented as a tunnel structure which can enhance electric and magnetic properties. A commercially available electromagnetic simulator CST Microwave Studio is utilized to design and investigate the eSRR (electric split-ring resonator) and tunnelled LC resonator structures. Furthermore, ADS (Advance Design software) is used to determine the scattering parameters of the equivalent circuit. The proposed metamaterial structure is employed as a sensor operating in the C-band (6.88 GHz) of the microwave region, and its sensing properties are tested using glossy paper as an obstacle. The designed metamaterial tunnelling structure exhibits very high sensitivity toward dielectric obstacles at different rotational angles and thus can be potentially used in various sensing applications. The field enhancement effects on sensing application are verified by measured obtained results for eSRR and tunnelled LC resonator structures.     

Modelling metamaterial transmission lines: a review and recent developments

This review paper is devoted to the discussion and comparison of the lumped element equivalent circuit models of the different types of metamaterial transmission lines that have been proposed so far, namely the CL-loaded lines, and those lines based on the resonant type approach. The latter category comprises both artificial lines loaded with split ring resonators (SRRs), or related topologies, and metamaterial transmission lines based on complementary split ring resonators (CSRRs). It will be the main aim of this paper to clearly justify the circuit elements of the models (and link such elements to the line physics and topology), to compare the different lines to the light of these models, and to point out the advantages and drawbacks of the different metamaterial transmission lines. As long as metamaterial transmission lines are exhaustively used for the design of compact microwave and millimeter wave components with improved performance and/or based on new functionalities, and their synthesis is based on the lumped element equivalent circuits, this paper is of actual interest for RF/microwave engineers and in general to those readers involved in metamaterial research and applications.     

基于等效介质原理的宽角超材料吸波体的理论分析

目前,很少有文章就如何实现宽角度吸波材料进行详细的理论分析和设计指导,设计宽角度吸波材料仍然是一件很困难的事情.本文基于等效介质理论对带有反射地板的单层介质超材料吸波体进行较为详细的理论分析.从基础电磁理论出发,推导TE波(横电波,电场方向与入射面垂直的平面电磁波)和TM波(横磁波,磁场方向与入射面垂直的平面电磁波)照射下吸波体的反射系数,分析实现宽角度吸波效果所需的等效电磁参数,为宽角度超材料吸波体的设计提供了理论基础.此外,论文还理论分析了实现宽带宽角吸波等效电磁参数所要满足的条件,并做了计算检验.结果表明,当介质等效电磁参数按照特殊曲线随频率发生变化时,理论上能实现宽带宽角的吸波效果.     

A flexible metamaterial with negative refractive index at visible wavelength

In this paper, we demonstrated a realization of a flexible metamaterial with negative refractive index operating at visible wavelength. With the help of Finite-Difference Time-Domain (FDTD) method, we could establish design rules for the metamaterial and analyze the characteristics of it. To this end, the fishnet structure with the unit cell size 185 nm by 240 nm was fabricated. Due to the polymer dielectric spacer between the metal-layers, the metamaterial is freestanding without base substrate and additional backside etching process.     

Robust stability characterizations of active metamaterials with non-Foster loads

Active metamaterials incorporating with non-Foster elements have been considered as one of the means of overcoming inherent limitations of the passive counterparts, thus achieving broadband or gain metamaterials. However, realistic active metamaterials, especially non-Foster loaded medium, would face the challenge of the possibility of instability. Moreover,they normally appear to be time-variant and in unsteady states, which leads to the necessity of a stability method to cope with the stability issue considering the system model uncertainty. In this paper, we propose an immittance-based stability method to design a non-Foster loaded metamaterial ensuring robust stability. First, the principle of this stability method is introduced after comparing different stability criteria. Based on the equivalent system model, the stability characterization is used to give the design specifications to achieve an active metamaterial with robust stability. Finally, it is applied to the practical design of active metamaterial with non-Foster loaded loop arrays. By introducing the disturbance into the nonFoster circuit(NFC), the worst-case model uncertainty is considered during the design, and the reliability of our proposed method is verified. This method can also be applied to other realistic design of active metamaterials.     

Temperature-controlled tunable acoustic metamaterial with active band gap and negative bulk modulus

The local resonant band gap and the negative bulk modulus of the acoustic metamaterial with Helmholtz resonators are strongly affected by the temperature of water. In this paper, the acoustic transmission line method (ATLM) is introduced to investigate the influences of the temperature of water on the local resonant band gap and the negative bulk modulus of the acoustic metamaterial. Results show that the relative variations of the local resonant band gap and the negative effective bulk modulus suffering from the change of the temperature of water are approximately equivalent and are up to about 11%. The reason is that the local resonant frequency is proportional to the sound speed of fluid which is strongly effects by the temperature of water. By achieving the unambiguous relationships between these unusual properties of the acoustic metamaterial and the temperature of water, we find that the temperature-controlled acoustic metamaterial with the active band gap and the active negative bulk modulus can be realized in theory. This idea opens a new avenue for the design of the tunable acoustic metamaterial that can modulate the acoustic wave propagation.     

Tunable terahertz metamaterial based on resonant dielectric inclusions with disturbed Mie resonance

Tunable metamaterial operating in terahertz (THz) frequency range based on dielectric cubic particles with deposited conducting resonant strip was investigated. The frequency of the first magnetic type Mie resonance depends on the electric length of the strip. It can be changed under photoexcitation or applied voltage. This method of control was used for a design of tunable double negative metamaterial based on dielectric resonant inclusions and wire medium.     

基于石墨烯编码超构材料的太赫兹波束多功能动态调控

提出了一种基于石墨烯带的太赫兹波段的1 bit编码超构材料,可以实现太赫兹波束的数目、频率、幅度等参数多功能动态调控.该结构由金属薄膜、聚酰亚胺、硅、二氧化硅、石墨烯带组成.通过对石墨烯带施加两种不同的电压,可以实现一定频率范围内相位差接近180?的"0"和"1"数字编码单元,进而构成1 bit动态可控的编码超构材料.全波仿真结果表明,不同序列的编码超构材料能够实现波束数目从单波束、双波束、多波束到宽波束的调控.相同序列的编码超构材料,通过施加石墨烯带的不同电压能够实现宽频段波束频率的偏移.对于000000或者111111周期序列的编码超构材料,通过施加石墨烯带的不同电压还能够实现波束幅度的调控.因此这种基于石墨烯带的编码超构材料为灵活调控太赫兹波提供了一种新的途径,将在雷达隐身、成像、宽带通信等方面具有重要的意义.     

Equivalent circuit analysis of terahertz metamaterial filters

An equivalent circuit model for the analysis and design of terahertz (THz) metamaterial filters is presented.The proposed model,derived based on LMC equivalent circuits,takes into account the detailed geometrical parameters and the presence of a dielectric substrate with the existing analytic expressions for self-inductance,mutual inductance,and capacitance.The model is in good agreement with the experimental measurements and full-wave simulations.Exploiting the circuit model has made it possible to predict accurately the resonance frequency of the proposed structures and thus,quick and accurate process of designing THz device from artificial metamaterials is offered.     

Multi-functional metamaterial sensor based on a broad-side coupled SRR topology with a multi-layer substrate

This paper intends to demonstrate the feasibility of a miniaturized multi-purpose metamaterial sensor that can be effectively used for chemical, biological and pressure sensing in microwave and terahertz applications. This novel sensor design makes use of the double-sided split ring resonator (DSRR) topology that is modified to have an additional sensing medium sandwiched between two identical broadside coupled SRR unit cells. The resonance frequency of the resulting DSRR sensor shifts as the dielectric permittivity or thickness of this interlayer medium changes in response to variations in an environmental parameter such as temperature, humidity, density, concentration or pressure. As a proof of concept study, both numerical and experimental results are presented with very good agreement for a multi-functional miniaturized metamaterial sensor prototype operating in X-band. Simulations for three different real-life scenarios are also presented for this sensor topology to demonstrate a moisture sensor, a density sensor and a temperature sensor with very good sensitivities where the interlayer medium is occupied by sawdust, silica aerogel and seawater, respectively.