Analysis of Transmission Characteristics for NRD/Microstrip Line Hybrid Integrated LSE and LSM-Mode Baluns*

The NRD/microstrip line hybrid integration structure shows good behavior for millimeter wave applications. This paper applies the integral equations method to analyze the transmission characteristics of the NRD/microstrip line hybrid integrated baluns coupling through slot and operating in LSE or LSM modes. To apply this method, a new Greens’ function of microstrip line is presented and the slot coupling problems between NRD guide and microstrip line and the practical LSE and LSM-mode baluns are analyzed respectively. The availability of the present approach is validated by rather good agreement between the theoretical results and the experiment data given in the literature.* Supported by the National Natural Science Foundation of China (No. 60371010) (No. 60471037)     

红敏聚乙烯醇/丙烯酰胺体系光致聚合物全息记录材料的空间分辨力增强研究

针对目前聚乙烯醇/丙烯酰胺体系光致聚合物材料的空间分辨力不高的问题,提出了一种采用低相对分子质量的聚乙烯醇作为成膜剂来改进光致聚合物分辨力的新方法.采用不同相对分子质量(72000,15000,9000)的聚乙烯醇成膜剂制成光致聚合物,对其衍射效率和空间分辨力等指标进行了对比实验.实验表明选用低相对分子质量(9000)的成膜剂可将该体系光致聚合物的分辨力提高到3000 line/mm以上,实验中仅需40 mJ/cm2左右的曝光量即可获得85%的衍射效率.另外,还对该材料的全息存储特性及其在角度复用全息存储方面的初步应用结果进行了报道.     

新型复合左右手传输线及其在滤波器设计中的应用

开环谐振器阵列由于结构庞大, 难以实现小型化, 而逆开环谐振器则由于刻蚀在接地板上, 容易对微波电路中其他部件造成干扰. 针对上述问题, 提出了一种新型双层介质复合左右手传输线结构, 并提取了其等效相对介电常数和等效相对磁导率, 然后分析了新结构的尺寸参数对其传输特性的影响程度, 最后将一种新型Minkowski分形曲线应用于该结构, 设计和制作了两款双频滤波器, 验证了该复合左右手传输线的双频特性.     

Accurate Design of Finline Tapers for Millimeter Wave Applications

The design of nonuniform bilateral finlines on anisotropic substrates for millimeter wave applications is presented. The taper consists of a planar circuit with smooth variation of the slot width profile along the structure. The spectral domain method and Galerkin procedure are combined with the transmission line theory for studying the behavior of tapered bilateral finlines and evaluation of their design parameters. The influence of the substrate anisotropy on the propagation characteristics of these structures is also examined. This technique is general and can be applied to investigate a broad class of planar transmission line tapers.     

Scattering theory and discrete-time quantum walks

We study quantum walks on general graphs from the point of view of scattering theory. For a general finite graph we choose two vertices and attach one half line to each, and consider walks that proceed from one half line, through the graph, to the other. The probability of starting on one line and reaching the other after n steps can be expressed in terms of the transmission amplitude for the graph.     

87Rb D1线法拉第反常色散光学滤波

为了得到在高背景噪音下对弱信号光的提取,实验研究了基于⁸⁷Rb D₁线5S_1/2F=2→5P_1/2 F'=1跃迁的795 nm法拉第反常色散光学滤波器.充铷的样品池所含⁸⁷Rb的比例高于自然铷,样品池处在均匀的磁场中并且夹在两个相互正交的偏振片之间.入射的探测光通过样品池,与原子相互作用,由于法拉第旋转效应实现滤波功能.改变实验条件,透射结果随之明显变化.当温度从340 K升高到360 K,透射谱的变化情况被细致记录,并且分析了导致透射情况变化的原因.在适当的工作温度以及磁场条件下,得到线宽为约220 MHz的超窄带透射谱线,谱线透过率约为48%.⁸⁷Rb D₁线的实验结果优于⁸⁵Rb的吸收线.     

Ferrimagnetic damping of epitaxial garnet film Yb1.7Eu1.3Ga0.5Fe4.5O12

The criterion for selecting rare-earth ions in iron garnet to achieve low damping and high magnetic mobility is established using the slow ferrimagnetic relaxation theory of Van Vleck and Orbach. Ytterbium and europium are excellent candidates to form mixed rare-earth iron garnet for magnetic bubble applications. An epitaxial film of Yb_1.7Eu_1.3Ga_0.5Fe_4.5O₁₂ was grown on a {111} gadolinium gallium substrate, and its low Landau-Lifshitz damping parameter λ/γ² = 1.1 × 10^?7 oe²-sec-rad^?1 was demonstrated by measuring the ferrimagnetic resonance line width.     

Conversion from constitutive parameters to dispersive transmission line parameters for multi-band metamaterials

Abstract

In this study, we explain an approach including conversion from constitutive parameters to dispersive transmission line parameters using the double-band DNG (double-negative) properties of the circular type fishnet metamaterials. After designing the metamaterial structure, the numerical calculations and the composite right/left-handed (CRLH) modeling of circular-type metamaterials are realized in free space. Detailed dispersion characteristics give us the opportunity to explain the true behavior of the inclusions during the analysis stage. By combining the results coming from the standard retrieval procedure with the conventional CRLH theory, we calculate the actual values of the transmission line parameters for all frequency regimes. The constitutive parameters of an equivalent CRLH transmission line are derived and shown to be negative values. It is shown that the constitutive parameters present the same behavior for all negative refractive index regimes. The double-negative properties and the phase advance/lag behavior of metamaterials are observed based on the dispersive transmission line parameters.     

Investigating the validity of existing definitions and empirical equations of effective length/area of grounding wire/grid for transient studies

There are various definitions for effective length/area of grounding wire/grid for lightning transients [A.S. Farag, T.C. Cheng, D. Penn, Grounding terminations of lightning protective systems, IEEE Trans. Dielectics, Elect. Insul 5(6) (1998) 869–877; B.R. Gupta, B. Thapar, Impulse impedance of grounding grid, IEEE Trans. Power Apparatus Syayem PAS-99(6) (1980) 2357–2362; Y. Liu, N. Theethayi, R. Thottappillil, An engineering model for transient analysis of grounding system under lightning strikes: non–uniform transmission line approach. IEEE Trans. Power Delivery 20 (2) (2005) 722–730; M.I. Lorentzou, N.D. Hatziargriou, Modelling of long grounding conductors using EMTP, in: IPST’99, International Conference on Power System Transients, Budapest, 20–24 June, 1999; L.D. Grcev, M. Heimbach, Frequency dependent and transient characteristics of substation grounding system, IEEE Trans. Power Delivery 12 (1997) 172–178.]. The present work investigates and discusses the validity of those existing definitions. Further, practical methods for estimating the effective length/area of different grounding structures are proposed for engineering applications. The calculations for effective length/area based on non-uniform transmission line approach (Liu et al., 2005) show that, for a single grounding wire, the empirical equation for effective length in Farag et al. (1998) is not valid when the injection current has very fast rise time. Also, the empirical equation for effective length of grid edge in Gupta and Thapar (1980) is not applicable for grids with large inner mesh size.     

基于光电反馈环单元时钟提取与解复用的160 Gb/s OTDM 信号100 km传输

提出了一种能够同时对高速光时分复用技术信号解复用与时钟提取的光电反馈环单元.在接收端,采用光电反馈环单元,信号单次通过即可同时完成160 Gb/s到10 Gb/s的解复用与时钟提取：两级电吸收调制器级联工作方式缩减了采样窗口宽度,满足了解复用小于6.25 ps超窄采样窗口的要求|而闭合环路的锁相同步工作方式,使所提取的时钟信号抖动（Jitter RMS）由2.4 ps降至450 fs.基于该结构,实验上成功实现了无误码的100 km 160 Gb/s光时分复用技术传输及传输后无误码地解复用与时钟提取,功率代价小于3 dB.     

Long period grating in/on planar and channel waveguides: A theory description

A comprehensive, complete theory suitable for a long period grating (LPG) on/in a planar or channel waveguide is described on the basis of coupled mode theory. The theory aims at key characteristic parameters with respect to the effect of the LPG, including resonance wavelength, transmission power of the guided mode in the waveguide, full-width at half-maximum (FWHM) of the power attenuation band in transmission spectrum of the guided mode, and coupling coefficient between a guided and a coupled mode. The type of the grating including relief and index modulation, different polarization state combinations of the guided mode and the resonant mode, and slanted grating structure are considered in this theory. The influences of the coupling between two guided modes and between a guided mode and a substrate mode are discussed. The role of cladding layer in a long period waveguide grating is demonstrated in particular. Finally, the expressions for the sensitivity of resonance wavelength as a function of external temperature, pressure and surrounding refractive index are derived.     

Effect of the Dielectric Anisotropy on the Propagation Properties of Microstrip Tapers with Height Variations

This paper deals with the design and application of nonuniform microstrip transmission lines on anisotropic substrates. A rigorous analysis is based on the use of Hertz vector potentials, moment method and transmission line theory to determine the dispersion characteristics of single and coupled tapered microstrip lines for accurate performance prediction. Results are presented for the main parameters providing the necessary information to design several devices on tapered microstrip, with variation on the strip width and dielectric height, for (M)MIC and antennas applications. A good agreement was observed with the results available in the literature for tapered lines on isotropic substrates.     

Theory of collision effects on atomic and molecular line shapes

A review of recent developments in the theory of the effects of binary collisions on the spectral profiles associated with atomic and molecular systems is presented. To consistently account for collisional perturbations of both the internal energy levels and the velocity of active (emitting or absorbing) atoms or molecules, one must use a theory in which the center-of-mass motion of the active atoms has been quantized. Following this procedure general equations for absorption or emission line shapes are obtained. The line shapes may exhibit narrowing or broadening with increasing perturber pressure, depending upon the nature of the collision interaction. The physical significance of the collision mechanisms giving rise to such behavior is discussed, as is the experimental evidence in support of the theory. Various applications of the theory are presented.     

ps脉冲传输线的多容性负载阻抗匹配模型和计算

 指出提高微带横截面取样速率的关键问题是传输线多容性负载阻抗匹配，根据分布参数理论和微波传输线理论，提出局部匹配模型，推导出阻抗匹配计算公式。数值模拟和电路仿真结果表明，局部补偿匹配法对不同工作频率下的多负载电容ps脉冲传输线均可进行较好的补偿，传输线上的各点取样波形失真度很小，补偿效果明显，可以提高微带横截面取样速率。     

可调谐一维特异材料(Metamaterial)的微波传输性质

利用变容二极管制作了可调谐一维左右手组合材料.并对其进行了传输系数测量.实验发现当电压升高时，左手通带将向高频方向移动，而禁带的终止频率保持不变.基于微波传输线理论，给出了这种左右手组合材料的色散方程，实验曲线与理论曲线能够很好地符合. 关键词： 调谐 特异材料 传输系数 变容二极管     

用改进的传输线算法计算水平层状横向同性地层中海洋可控源电磁响应

利用二维Fourier变换与电磁场分解技术将层状横向同性地层中Maxwell方程转化成两个独立的关于横磁(TM)波和横电(TE)波的传输线方程; 借助传输线理论与叠加原理, 仅利用电流源传输线Green函数得到TM波和TE波的解, 改进传输线算法, 建立横向同性地层中频率-波数域电流源电场和磁场并矢Green函数的新算法与新的解析表达式, 提高海洋可控源电磁响应数值模拟效率. 在此基础上, 利用传输线Green函数的基本解以及边界条件, 推导出广义反射系数与振幅递推公式, 得到各个地层中传输线Green函数的解析解; 然后利用Fourier逆变换与Bessel公式将海洋可控源电磁响应表示为Sommerfeld形式的积分, 借助三次样条插值与Lommel积分公式快速计算其数值解. 通过数值模拟结果考察工作频率以及地层各向异性电阻率变化等对海洋电磁响应的影响. 关键词： 传输线法 横向同性地层 海洋可控源电磁 Sommerfeld积分     

Control of the sensitivity of CRLH interdigital microstrip balanced structures using a co-design genetic algorithm approach

A fully automated tool for designing CRLH interdigital microstrip structures using a co-design synthesis computational approach is proposed and demonstrated experimentally. This approach uses an electromagnetic simulator in conjunction with a genetic algorithm to synthesize and optimize a balanced CRLH interdigital microstrip transmission line. The high sensitivity of a long balanced transmission line to fabrication tolerances is controlled by the use of a high precision 3D simulator. The 2.5D simulator used was found insufficient for a large number of unit cells. A 13 UC CRLH transmission line is designed with the proposed approach. The response sensitivity of the balanced transmission lines to the over/under-etching factor is highlighted by comparing the measurements of four lines with different factors. The effect of over/under-etching is significant for values larger than 10 μm.     

Hadron spectroscopy and structure from AdS/CFT

The AdS/CFT correspondence between conformal field theory and string states in an extended space-time has provided new insights into not only hadron spectra, but also their light-front wave functions. We show that there is an exact correspondence between the fifth-dimensional coordinate of anti-de Sitter space z and a specific impact variable ζ which measures the separation of the constituents within the hadron in ordinary space-time. This connection allows one to predict the form of the light-front wave functions of mesons and baryons, the fundamental entities which encode hadron properties and scattering amplitudes. A new relativistic Schr?dinger light-front equation is found which reproduces the results obtained using the fifth-dimensional theory. Since they are complete and orthonormal, the AdS/CFT model wave functions can be used as an initial ansatz for a variational treatment or as a basis for the diagonalization of the light-front QCD Hamiltonian. A number of applications of light-front wave functions are also discussed.     

Synthesis and structure determination of bimetallic Au/Cu nanoparticles

The synthesis of bimetallic nanoparticles has become so important in recent times due to its multi-faceted applications. The structure of the synthesised particles influences directly their properties. In this paper, we report the synthesis of Au/Cu nanoparticles by a simultaneous reduction method, considering three different molar concentrations (AuCu, AuCu₃ and Au₃Cu) of the components. In order to determine the size and structure of the obtained clusters, the particles were examined by optical spectroscopy, transmission electron microscopy and high-resolution transmission electron microscopy. One of the major factors, the minimum bimetal formation energy, was calculated by an embedded-atom method. The relation between the Au/Cu proportions has been demonstrated to affect the size of the particles and the corresponding structures. From the basic structural analysis it is found that the particles were fcc-like, multiple twin or multiple defect particles for the different Au/Cu concentrations. The smallest particles were identified for the Au/Cu sample with 50% of each, and the most crystalline structures were also obtained in the same sample. PACS 61.46.+w; 61.16.-d; 31.15.Qg