An overview of near-field antenna measurements

After a brief history of near-field antenna measurements with and without probe correction, the theory of near-field antenna measurements is outlined beginning with ideal probes scanning on arbitrary surfaces and ending with arbitrary probes scanning on planar, cylindrical, and spherical surfaces. Probe correction is introduced for all three measurement geometries as a slight modification to the ideal probe expressions. Sampling theorems are applied to determine the required data-point spacing, and efficient computational methods along with their computer run times are discussed. The major sources of experimental error defining the accuracy of typical planar near-field measurement facilities are reviewed, and present limitations of planar, cylindrical, and spherical near-field scanning are identified.     

Shorted fractal Sierpinski monopole antenna

A novel configuration of a shorted fractal Sierpinski gasket antenna is proposed. Using only half the structure of a conventional Sierpinski gasket, the antenna is folded over to be parallel to the ground plane, to form an element that is, in some ways, similar to the inverted L antenna. A shorting pin is then placed at the far end of the antenna. A quasi log periodic resonance behaviour is observed     

Generalized Sierpinski fractal multiband antenna

A new set of fractal multiband antennas called mod-p Sierpinski gaskets is presented. Mod-p Sierpinski fractal antennas derive from the Pascal triangle and present a log-periodic behavior, which is a consequence of their self-similarity properties. Mod-p Sierpinski fractal antennas constitute a generalization of the classical Sierpinski antenna     

新型RF-MEMS可重构分形天线

设计了一种新型的集成RF-MEMS开关的混合分形可重构天线,该天线为加载了1阶Koch曲线的1阶Sierpinski三角垫片结构.仿真结果表明:所设计的天线在MEMS开关全闭合和全断开的状态下分别具有多个不同的工作频带.详细地分析了天线的重构特性,按照仿真模型在高阻硅片上运用微电子工艺制作出了天线样品.对样品进行了测试,最后比较和分析了测试结果.     

Shorted fractal Sierpinski monopole antenna

This paper describes novel configurations of shorted fractal Sierpinski gasket antenna. The antenna uses half the structure of a conventional Sierpinski gasket antenna and is folded over to be parallel to the ground plane, to form an element similar to that of the inverted L antenna. A quasi log periodic resonance behavior is obtained with a shorting pin placed at the far end of the antenna. Several configurations are shown and a design using two shorting pins which improves the bandwidth at the fundamental band is also demonstrated.     

Design of miniaturised ISM-band fractal antenna

Miniaturisation techniques for antenna designs based on fractal geometries are of growing interest in wireless communications. Described is the design of a miniaturised fractal antenna prototype. To this end, a particle swarm optimiser is used to optimise simultaneously the fractal shape and the input impedance by acting on the thickness of the antenna segments to avoid matching networks. The effectiveness of the approach is confirmed by simulated and experimental results.     

加短路过孔的谢尔宾斯基毯式分形贴片天线研究

在传统谢尔宾斯基（Sierpinski）毯式分形贴片天线的基础上,加上两个短路过孔,使天线能够工作于更多的频段,并且在保持天线体积不变的情况下,使天线的第一频点降低到原来的一半。对所加短路过孔的位置和直径与天线的工作频点之间的关系进行了研究。使用高频电磁仿真软件（HFSS）仿真软件给出了天线S11和方向图的仿真结果,制作了实际的天线,给出了S11实验结果。实验结果与仿真结果基本吻合。     

A new ultra-wideband fractal monopole antenna

The paper focuses on the peculiar dynamic behaviour of the recently developed 8 mm² TO-220-packaged, high-voltage, double-interdigitated (or rwo interdigi-tation levels—TIL) GTO thyristor. This novel power device was rated under both slightly and heavily inductive resistive loads, i.e. close to the real conditions encountered in practical power circuits employing GTO thyristors. Emphasis is laid on the ability of TIL GTOs to switch safely, with minimum power losses, a certain amount of anode current under high-voltage conditions and high commutation frequencies. The merits of TIL GTO thyristors are analysed in terms of their reliability and switching efficiency, which include the total power losses (conduction and switching losses), turn-on and turn-off gains and the switching speed. It is shown that thanks to their built-in self-protective features, these novel GTOs possess an enhanced current-handling capability at commutation frequencies up to 50kHz under extremely tough load conditions. The main implications of the results for power applications are outlined.     

Compact CPW-fed Sierpinski fractal monopole antenna

A novel compact and uniplanar CPW-fed Sierpinski fractal monopole antenna is presented. A fractal radiating element represents the fourth iteration of the Sierpinski gasket with scale factor /spl delta/=1.5. The antenna is printed on a single layer dielectric substrate and fed by 50 /spl Omega/ CPW transmission line. The multiband operation of the planar fractal structure is confirmed experimentally.     

Broadband circularly-polarised Spidron fractal slot antenna

A broadband circularly-polarised fractal antenna is proposed, designed, and tested. The concept of a novel Spidron fractal system is employed to achieve both broadband and circular-polarisation characteristics. Presented is the first known application of a Spidron fractal to antenna design. A simple 50 ω microstrip line is used to excite the Spidron-shaped slot. The total dimensions of the fabricated antenna are 40 X 40 X 1.52 mm³. The measured -10 dB return loss bandwidth and the 3 dB axial ratio bandwidth are 78.3 and 15.2%, respectively. The peak gain of the antenna is 4.3 dBi.     

An iterative model for fractal antennas: application to theSierpinski gasket antenna

A simple model that explains the behavior of the Sierpinski fractal antenna is presented. This model shows that the multiband behavior of the Sierpinski fractal antenna is a consequence of its fractal nature. The model is applied to predict the behavior of the Sierpinski fractal antenna when the flare angle is modified and its validity is assessed by comparing its predictions with measured data     

An overview of routing optimization for internet traffic engineering

Traffic engineering is an important mechanism for Internet network providers seeking to optimize network performance and traffic delivery. Routing optimization plays a key role in traffic engineering, finding efficient routes so as to achieve the desired network performance. In this survey we review Internet traffic engineering from the perspective of routing optimization. A taxonomy of routing algorithms in the literature is provided, dating from the advent of the TE concept in the late 1990s. We classify the algorithms into multiple dimensions: unicast/multicast, intra-/inter- domain, IP-/MPLS-based and offline/online TE schemes. In addition, we investigate some important traffic engineering issues, including robustness, TE interactions, and interoperability with overlay selfish routing. In addition to a review of existing solutions, we also point out some challenges in TE operation and important issues that are worthy of investigation in future research activities.     

分形倒L天线的研究

构建了一种紧凑结构的分形倒L天线,用矩量法对天线的阻抗特性、辐射方向图特性和天线电流分布作分析研究,并进行实验验证.结果表明,分形倒L天线不仅大大降低了天线的高度,而且有效地缩减了天线的水平长度,是天线小型化设计的重要方法.     

Microstrip fractal patch antenna for multiband communication

A novel square microstrip fractal patch antenna in a Sierpinski carpet is proposed for three-band operation. Measured results indicate that the return loss is better than 10 dB and that the gain is greater than 7 dB in each band. This antenna is an attractive candidate for wireless, satellite and mobile communication applications     

具有三陷波特性的类Sierpinski分形超宽带天线

为避免窄带通信系统对超宽带(ultra-wideband,UWB)系统的干扰冲突,提出一款具有三陷波特性的类Sierpinski分形UWB天线.辐射贴片采用圆环与五角星形嵌套迭代的2阶类Sierpinski分形结构,并采用缺陷地结构接地板以实现良好的UWB特性.通过在分形结构的上部添加对称倒L形开路枝节,在微带馈线两侧添加对称L形开路枝节,并在馈线处刻蚀倒π形窄缝隙产生了4.5～4.8 GHz、7.2～7.8 GHz和8.0～8.5 GHz三个频段的陷波特性.仿真和实测结果表明,天线在3.1～18.1 GHz的频段内,可有效抑制国际卫星波段、X卫星波段和国际电信联盟波段等窄带系统的干扰.该天线除滤波频段内,在通带频段内有较稳定的增益和全向辐射特性,可用于各种UWB系统中.     

具有三陷波特性的类Sierpinski分形超宽带天线

为避免窄带通信系统对超宽带(ultra-wideband,UWB)系统的干扰冲突,提出一款具有三陷波特性的类Sierpinski分形UWB天线.辐射贴片采用圆环与五角星形嵌套迭代的2阶类Sierpinski分形结构,并采用缺陷地结构接地板以实现良好的UWB特性.通过在分形结构的上部添加对称倒L形开路枝节,在微带馈线两侧添加对称L形开路枝节,并在馈线处刻蚀倒π形窄缝隙产生了4.5～4.8 GHz、7.2～7.8 GHz和8.0～8.5 GHz三个频段的陷波特性.仿真和实测结果表明,天线在3.1～18.1 GHz的频段内,可有效抑制国际卫星波段、X卫星波段和国际电信联盟波段等窄带系统的干扰.该天线除滤波频段内,在通带频段内有较稳定的增益和全向辐射特性,可用于各种UWB系统中.     

High directivity fractal boundary microstrip patch antenna

A novel patch antenna with a fractal boundary condition is proposed. Experimental and numerical results corroborate the fact that the fractal characteristic of the perimeter produces localised modes. This property is utilised in the design of a microstrip patch antenna with a measured directivity of 12.7 dB     

An overview of optical device research in China

An overview of research activities in China on the following optical communications devices is presented: quantum-well semiconductor lasers; distributed feedback laser diodes; wideband, tunable, narrow-linewidth, external-cavity laser diodes, semiconductor and doped-fiber amplifiers; laser-diode-pumped solid state and single-crystal fiber lasers; doped fiber ring lasers, optical modulators; switches; bistable devices; experimental wavelength-division-multiplexed (WDM) systems; and time-division photonic switching systems. The most important of these technologies are highlighted with respect to demonstrated achievements in China. The potential uses of these technologies in future telecommunications systems are discussed     

一种二叉树状分形偶极子天线的设计

提出了一种基于二叉树状分形结构的分形偶极子贴片天线。该天线的介质基片采用相对介电常数为4.4,介电损耗角正切为0.02的FR4介质板,由微带线经阻抗变换后进行馈电。该天线利用分形技术实现了33%的尺寸缩减;通过平行双线结构和开U型槽技术,优化了阻抗匹配,降低了天线的谐振频率。通过仿真分析与模型优化,天线的最终尺寸为35 mm×22 mm×1.6 mm,中心工作频率为2.87 GHz,工作频率为2.77~2.97 GHz,-10 dB阻抗相对带宽为6.9%,工作频带内最小回波损耗可达-49 dB,最大增益可达2.36 dB。该天线具有小型化、阻抗匹配良好的优点,在当代小型化通信系统中具有良好的应用前景。