一种分析二维平面左手结构的新方法

本文提出了一种基于单元结构的四端口网络S参数和周期性结构的Bloch理论来分析二维平面分布参数左手结构的新方法,以及基于Bloch波数和Bloch阻抗来判断左右手特性频带的新方法.与以往的单元结构分析方法相比,本文方法有利于单元结构的灵活设计,能较好地考虑分布参数元件色散特性,能简便准确地判断出左右手特性频带,且能用于分析各向异性和有损耗结构.作为例子,我们设计了一种串联电容增强型平面左手结构,并用本文方法进行分析,清楚地得到了该结构的左右手特性频带.本文还采用时域有限差分方法(FDTD)对这种新型平面结构阵列进行模拟,在左手特性频带内得到了后向波传播特性,从而验证了本文方法的有效性.     

改进的宏元胞法及其在一维人工周期传输线色散性能提取中的应用

针对传统宏元胞法时效性低通用性弱的缺陷,提出了一种改进的宏元胞法,即将相移常数的多值问题转化为对同一周期结构相位解卷绕起始频点的判定问题,如此可方便地提取出唯一精确的相移常数.由于新方法严格考量了元胞间电磁场的互耦效应,仅需一次仿真或实测便可计算出元胞间存在任意耦合强度的一维人工周期传输线的色散和Bloch阻抗性能.运用新方法提取了经典的非平衡态和平衡态互易非对称微带复合左右手传输线的色散特性,并与传统的本征模式法、解卷绕法和单元胞法的提取结果进行了对比.进一步利用改进宏元胞法和解卷绕法的提取结果分别反演出微带复合左右手传输线的S参数,基于改进宏元胞法解的S参数与全波仿真S参数之间良好的一致性证实了新方法的精确性.     

谐振-传输线复合结构左手材料设计

提出了一种谐振-传输线复合结构左手材料单元.该结构基于谐振型左手材料、复合左右手传输线理论设计,可在不同排列方式下产生多种左手特性.基于曙光云计算服务平台,分析了该材料单元结构的谐振特性、单元阵列的传输线特性,并进一步对其谐振特性中的负折射特性进行了仿真验证.实验表明:单一结构单元条件下,该结构可体现出由谐振特性产生的左手频带;在阵列条件下,可同时体现出左右手传输线特性以及谐振型左手特性.该结构的多种左手特性,或可在5.8 GHz频率范围内民用级微波器件领域获得广泛应用.     

基于交叉结构的混合左右手传输线单元设计

提出了一种基于交叉结构的混合左右手传输线(CRLH-TL)单元的设计方法。基于CRLH-TL理论,结合交叉结构单元的等效电路,分析其Bloch阻抗及Bloch传播常数,并采用电磁仿真软件构建出3层介质板的微带线结构来进行物理实现。仿真结果表明,此交叉结构CRLH-TL的带宽为20.2GHz,插入损耗低于0.5dB,回波损耗大于10dB。中心频率为6GHz,此时传输线的相移为0。结果表明,此基于交叉结构的CRLH-TL结构小巧,性能良好。     

基于Minkowski分形CRLH结构的微带漏波天线

将Minkowski分形理论应用于文献中提出的复合左右手传输线结构,使其带宽从2.78～3.30 GHz展宽到2.02～4.53 GHz.对新结构色散特性进行分析,给出色散曲线,确认其为平衡结构,并在此基础上设计了一款微带漏波天线.由于复合左右手单元结构具有左手和右手特性,漏波天线可以分别实现后向辐射和前向辐射,在平衡状态下,消除了平衡点附近的阻带效应,平衡点处的群速不为0,有行波传播,天线可产生横向辐射.仿真和测试结果表明,该文所设计的漏波天线工作频段为2.35～3.20 GHz,相对带宽为30.6％,且能实现从后向到前向连续辐射,克服了传统漏波天线后向辐射角和前向辐射角不连续的缺点.     

基于微带结构双左手频带左手材料的研究

介绍了混合左右手材料传输线的传输特性和分析方法。混合左右手材料的两个通带分别出现在2.5 GHz和6 GHz处。通过仿真获得S₁₁、S₂₁和色散曲线,从理论上验证了左手特性的存在。具有双左手频带的左手材料将在未来四频器件中得到广泛应用。     

矩形波导中左右手材料光子晶体的色散特性研究

研究了在矩形波导E平面填充的一维周期或准周期左右手材料光子晶体中电磁波的色散特性.采用传输矩阵法推导出一种适用于任意一维光子晶体E面填充矩形波导的2×22×2阶特征矩阵.定量分析了周期光子晶体中单元结构的重复次数、光子晶体的排列方式(周期,斐波那契,Thue-Morse和Octonacci排列)、及左手/右手材料介电常...     

周期性缺陷接地结构的微带线

基于单元缺陷接地结构(DGS)等效电路模型,研究了周期性缺陷接地结构微带线的色散关系,并给出其阻带的快速估算方法.为提高微波电路的集成度和灵活性,提出了基于周期性DGS结构弯折型微带线,分析其带阻特性、色散特性和阻抗特性.实验证明,该结构在4～7GHz之间具有良好的宽阻带特性.     

非谐振型结构的复合左右手带通滤波器小型化设计

提出了一种非谐振型结构的复合左右手带通滤波器，可应用于WLAN频段，该结构只采用一个复合左右手传输线单元，单元内部的交指结构提供等效左手电容，过孔结构提供等效左手电感，单元内部存在交叉耦合，通过调整交叉耦合电容和左右手参数，可产生2个可控传输零点并缩减尺寸，通过添加DGS缺陷地结构，能进一步优化滤波器性能，经过仿真优化最终设计出一款具有较高选择性、较好带外抑制性能的带通滤波器。实测结果显示:滤波器工作频率为5.98ＧＨｚ，3ｄＢ带宽为940 ＭＨｚ，带内插损最大值为1.59ｄＢ，相比传统滤波器设计，该结构大幅度减小了器件体积。     

一种X型宽带复合左右手传输线的设计与分析

为了实现宽带复合左右手传输线,提出并设计了一种反对称X型周期性左右手传输线结构.建立了结构的集总参数等效电路模型,并通过提取等效电路的元件值和S参数仿真,验证了传输线结构的谐振特性.采用参数反演算法对传输线结构的本构参数进行了提取和分析,证实了该结构具有1.6GHz的带宽,其中在10.08~10.9GHz呈现左手特性,在9.3~10.08GHz呈现右手特性,属于宽带左右手传输线结构.最后,应用印刷电路板技术制作了X型复合左右手传输线,并利用平板波导系统对其S参数进行了测试,实验测试结果和仿真结果吻合较好,证明了所设计的左右手传输线结构的有效性.为宽带左右手传输线结构的设计和分析提供了一种手段.     

A New Approach for the Analysis of Planar Distributed Two-Dimentional (2-D) Left-Haned (Lh) Structures

A new approach is proposed to analyze planar distributed 2-D LH structures. The 4-port S parameters of the unit cell combined with the Bloch-Floquet theory are used to determine the dispersion relations and Bloch impedance. The LH and RH frequency bands are identified by the signs of the real parts of the wave number and the Bloch impedance. Several advantages of the new approach over the previous unit cell analysis methods are presented. As an example, a capacitance-enhanced LH structure is designed and analyzed with the new approach. FDTD simulation is also performed to study the periodic LH structure with infinite arrays. The results of the simulation at the LH frequency band show the backward wave properties in consistent with those obtained by the proposed approach.     

Planar distributed structures with negative refractive index

Planar distributed periodic structures of microstrip-line and stripline types, which support left-handed (LH) waves are presented and their negative refractive index (NRI) properties are shown theoretically, numerically, and experimentally. The supported LH wave is fully characterized based on the composite right/left-handed transmission-line theory and the dispersion characteristics, refractive indexes, and Bloch impedance are derived theoretically. In addition, formulas to extract equivalent-circuit parameters from full-wave simulation are given. Open (microstrip) and closed (stripline) structures with a 5/spl times/5 mm/sup 2/ unit cell operating at approximately 4 GHz are designed and characterized by full-wave finite-element-method simulations. A 20 /spl times/ 6 unit-cell NRI lens structure interfaced with two parallel-plate waveguides is designed. The focusing/refocusing effect of the lens is observed by both circuit theory and full-wave simulations. Focusing in the NRI lens is also observed experimentally in excellent agreement with circuit theory and numerical predictions. This result represents the first experimental demonstration of NRI property using a purely distributed planar structure.     

平面微波光子晶体表面波带隙的直线法分析

运用直线法对一种以微带基片为载体的平面微波光子晶体进行了分析.详细介绍了直线法分析过程,并对直线法中阻抗矩阵的提取方式作出了改进.在不同的周期边界条件下,通过对由直线法所得的特征方程的求解,得出所对应的本征频点,从而求得整个平面微波光子晶体的表面波色散图,标明表面波带隙所在.文中分别对矩形贴片型以及环形贴片型光子晶体进行了分析.     

Microwave modeling of 2-D active grid antenna arrays

A new measurement technique for determining the broadband driving point impedance of large two-dimensional active grid arrays is presented. The active array radiates a plane wave in the broadside direction when all elements are locked in phase. For analysis, the array is reduced to a single unit cell by exploiting the array symmetries. The driving point impedance of the unit cell is determined by using the dielectric waveguide measurement method (DWM). The approximations of the method are discussed, and the method is compared with other measurement techniques. Results are presented for four square arrays: dipole, bow-tie, double-vee and slot array. The measurement method is verified by comparing it to the full-wave theory in the whole range. It is shown that all four antenna arrays can be represented by very simple circuits that use only transmission lines as circuit elements. The bow-tie array is found to represent the best choice for broadband operation     

A CPS Leaky-Wave Antenna With Reduced Beam Squinting Using NRI-TL Metamaterials

A reduced beam-squinting printed leaky-wave antenna (LWA) is proposed, comprising cascaded negative-refractive-index transmission-line (NRI-TL) metamaterial unit cells. Each NRI-TL unit cell is implemented in co-planar strip (CPS) technology and consists of a host TL loaded with series interdigitated capacitors and shunt meandered inductors. Periodic analysis is applied to the NRI-TL unit cell in order to extract the dispersion and Bloch impedance characteristics. Subsequently, the angular variation of the main radiated beam with frequency or ldquobeam squintingrdquo is derived, based on the expression for the Bloch propagation constant of the NRI-TL line. It is shown that by operating the LWA in the upper right-handed band where the phase and group velocities are closest to the speed of light, the beam squinting that the antenna experiences can be minimized. The theoretical performance of the LWA is verified through full-wave simulations and measurements of a fabricated prototype designed to produce a radiated beam at an angle of at GHz. This 20-element NRI-TL LWA exhibits a measured return-loss bandwidth below dB of 0.91 GHz (18.2%), and an average beam squint of 0.031/MHz. The proposed NRI-TL LWA is uniplanar, differential and broadband, and therefore suitable for integration with other microwave components and devices.     

折叠波导慢波电路的传输特性

研究了新型慢波结构折叠波导慢波电路的传输特性 ,利用等效电路法计算了折叠波导电路的色散特性、耦合阻抗和止带。分析和计算表明 ,该电路很适合用作短厘米波和毫米波大功率行波管的慢波结构。     

含正负材料的一维光子晶体的光学特性研究

为了得到新的传输性质,把具有负介电常数和磁导率的负折射率材料引入到光子晶体当中,运用Maxwell电磁波方程和Bloch理论得到的含正负折射率材料的色散关系的解析式,分别分析一维无限周期且正折射率材料和负折射率材料交替组成的一维光子晶体的禁带结构和色散特性,并与常规的正折射率材料的光子晶体比较,发现含正、负折射率材料且呈周期性重复的双层结构的复合光子晶体其光子具有较宽禁带,为设计超宽禁带的光子带隙结构提供了一定的理论可能性。     

A simple numerical analysis of planar optical waveguides using waveimpedance transformation

A simple numerical approach for studying arbitrary profile planar optical waveguides based on wave impedance transformation is presented. The only mathematics involved in this approach is the wave impedance transformation formula, which has been widely used in the field of microwaves. Because of its simplicity, the method can be implemented in short but effective computer codes. The method is exact when the index profiles are of step-index shapes and is shown to be very accurate in comparison with the exact analytical solutions for graded refractive index profiles