Science Letters: Lattice type transmission line of negative refractive index

In this letter, we introduce a novel passive transmission line of negative refractive index (i.e., left-handedness) based on identical symmetrical lattice type structures [thus called "lattice type transmission line" (LT-TL)]. The dispersion characteristic and the transmission response of the proposed LT-TL are analyzed. While all the other left-handed passive transmission lines are of high pass, the present passive left-handed transmission line is of low pass. Compared with a conventional transmission line, the LT-TL has a phase shift of 180° in the entire wide pass-band.     

Review: Research progress on Fabry-Perot resonator antenna

The Fabry-Perot resonator (FPR) antenna has found wide applications in microwave and millimeter waves and recently attracted considerable interest, in this paper, a summary of planar and cylindrical structures, analytic models and research development is presented, and a comparison between these structures and analytic models is made, showing that such analytic models as the FP cavity mode, electromagnetic band gap (EBG) defect mode, transmission line mode, and leaky-wave mode are consistent when applied to analyze this type of resonator antenna. Some interesting topics under recent research, including dual or multi-band, improvement of gain bandwidth, low profile and beam control, are surveyed.     

Science Letters: Lattice type transmission line of negative refractive index

In this letter, we introduce a novel passive transmission line of negative refractive index （i.e., left-handedness） based on identical symmetrical lattice type structures [thus called ＂lattice type transmission line＂ （LT-TL）]. The dispersion characteristic and the transmission response of the proposed LT-TL are analyzed. While all the other left-handed passive transmission lines are of high pass, the present passive left-handed transmission line is of low pass. Compared with a conventional transmission line, the LT-TL has a phase shift of 180° in the entire wide pass-band.     

Research progress on Fabry-Perot resonator antenna

The Fabry-Perot resonator （FPR） antenna has found wide applications in microwave and millimeter waves and recently attracted considerable interest. In this paper, a summary of planar and cylindrical structures, analytic models and research development is presented, and a comparison between these structures and analytic models is made, showing that such analytic models as the FP cavity mode, electromagnetic band gap （EBG） defect mode, transmission line mode, and leaky-wave mode are consistent when applied to analyze this type of resonator antenna. Some interesting topics under recent research, including dual or multi-band, improvement of gain bandwidth, low profile and beam control, are surveyed.     

Transmission line realization of subwavelength resonator formed by a pair of conventional and LHM slabs

INTRODUCTION Left-handed materials (LHMs), first investigated theoretically by Veselago (1968), have received sub- stantial attention in the scientific and engineering communities. The unique properties of these meta- materials are promising for a diversity of microwave applications, such as new types of beam steerers, modulators, filters, superlens (Pendry, 2000), cou- plers and antenna radoms (Smith et al., 2004). Re- cently, a transmission line (TL) approach has been successfully in…     

Broad-bandwidth and low-loss metamaterials： theory, design and realization

In this paper, we summarize some recent activities in the field of metamaterial research at the National University of Singapore （NUS）. Integral equations are applied for electromagnetic modelling of supernatural materials. Some special characteristics of the metamaterials are shown. Moreover, quasi-static Lorentz theory and numerical method （i.e., the method of moments for solving the electric field integral equation） and the transmission line theory are both presented to obtain the effective constitutive relations of metamaterials, respectively. Finally, feasibility of fabricating metamaterials based on analysis of equivalent transmission line model in the microwave spectrum and even higher is also shown and correspondingly some broad-bandwidth and low-loss metamaterial structures are designed and synthesized.     

Review:Broad-bandwidth and low-loss metamaterials:theory, design and realization

INTRODUCTION Conventional materials have positive magnetic permeability and mostly positive electrical permittiv- ity. Veselago (1968) initially assumed a material with negative permittivity and permeability simultane- ously and theoretically demonstrated the abnormal electromagnetic properties. This material, referred to as left-handed material (LHM) or metamaterial, re- verses a basic feature of light, such as, the reversal of the Doppler shift for radiation, and negative refractive in…     

超高压输电线路方向高频保护新原理(英文)

利用载波或微波通道实现的方向保护最适用于远距离超高压输电线路,在电力系统中得到广泛应用,这种保护的关键元件是用于判别故障方向的方向继电器．为了克服传统方向元件的缺点,提出基于人工神经网络的方向高频保护,通过电磁暂态仿真程序（ＥＭＴＰ）的广泛测试,证明基于人工神经网络的方向高频保护在任何运行状态和故障条件下都能正确识别被保护输电线路的各种故障模式（如故障方向和相别）,完全满足超高压输电线路对保护的要求．     

A new class of negative refractive index transmission line

We propose a new class of negative refractive index transmission line in which ideal operational amplifiers are applied to form the periodically loaded negative-impedance-converted inductors and capacitors. The phase response of the new trans-mission line is opposite to that of a positive refractive index conventional transmission line. Unlike the existing negative refractive index transmission line,the new negative refractive index transmission line is non-dispersive and thus can lead to many novel applications such as designing new broadband devices.     

平面天线阵列馈电网络应用教学探讨

在综合分析了微带平面天线阵列馈电网络的两种传统馈电方式的基础上,提出了一种在微波工程应用中实际使用的一种新型馈电网络,提高学生理论知识与实践相结合的能力,更好的掌握最新技术发展。其新型馈电网络由一种左-右手混合微带传输线构成,可以获得高于传统并联馈电网络的天线阵列增益;同时,可以修正传统串联馈电网络的天线阵列辐射方向图的波束偏移,给出了一个工作频率为35GHz的2×2微带面阵的馈电网络设计案例,验证了其理论的正确性。     

电容器在配电网输电线路上的无功补偿分析

随着城乡配电网的改造,大量用电负荷的出现导致输电线路上无功不足、电压偏低,进而影响到居民用电的质量。本文以江夏大桥新区某线路为例进行分析,确定电容器如何在线路上进行无功补偿。     

电磁场传输线理论仿真实验的设计与实现

通过对传输线理论教学内容及教学中存在问题的分析,针对传输线3种工作状态、行驻波瞬态分布以及基于Smith圆图的阻抗匹配等教学内容,设计并实现了传输线理论仿真实验。该实验内容突出知识的综合性与应用性,以达到良好的教学效果。     

Effects of un-transposed UHV transmission line on fault analysis of power systems

The conventional fault analysis method based on symmetrical components supposes that the three-phase parameters of un-transposed transmission line are symmetrical in case of fault. The errors caused by the method with the symmetrical distributed parameter circuit model as the equivalent circuit of the un-transposed ultra high voltage (UHV) transmission line were studied under both normal operation and fault, and the corresponding problems arising were pointed out. By contrast with electromagnetic transient and power electronics (EMTPE) simulation results with the asymmetrical distributed parameter circuit model of un-transposed line, it is shown that the conventional method cannot show the existence of negative and zero sequences before fault happening and there are many errors on voltage and current after fault happening which are different with fault types. The error ranges of voltage and current are 2.13%-81.13% and -7.82%-86.15%, respectively.     

电力线上的家电网络控制系统的设计

介绍了利用电力线MODEM芯片ST7536，采用电力载波形式，设计出了一个家电网络控制系统，对家电网络进行远程集中控制，可以对多路家用电器的运行情况进行实时监测和控制。     

Science Letters:Dual structure of composite right/left-handed transmission line

INTRODUCTION An artificial dielectric medium that exhibits si- multaneously negative electric permittivity and magnetic permeability, also known as a left-handed (LH) material, was first envisaged by Veselago, who theoretically predicted that such a medium would exhibit a negative refractive index (NRI) (Veselago, 1968). An artificial NRI medium exhibiting back- ward-wave propagation characteristics (and therefore a negative refractive index) was first realized ex- perimentally in (She…     

Modern travelling wave based fault location techniques for HVDC transmission lines

The modern travelling wave based fault location principles for transmission lines are ana-lyzed. In order to apply the travelling wave principles to HVDC transmission lines, the special tech-nical problems are studied. Based on this, a fault locating system for HVDC transmission lines is developed. The system can support modern double ended and single ended travelling wave princi-ples simultaneously, and it is composed of three different parts: travelling wave data acquisition and processing system, communication network and PC based master station. In the system, the fault generated transients are induced from the ground leads of the over-voltage suppression ca-pacitors of an HVDC line through specially developed travelling wave couplers.The system was applied to 500 Kv Gezhouba-Nanqiao(Shanghai)HVDC transmission line in China. Some field op- eration experiences are summarized, showing that the system has very high reliability and accu- racy,and the maximum location error is about 3 km(not more than 0.3% of the total line length). Obviously, the application of the system is successful, and the fault location problem has finally been solved completely since the line operation.     

双折射作用下横向受力光纤光栅反射谱的仿真研究

仿真分析了光纤布拉格光栅(FBG)横向受力时的双折射现象及其光纤光栅横向局部受力时的光谱变化,并进一步分析了双折射对横向局部受力光纤光栅的影响。当FBG横向局部受力部分较大时,光纤双折射对反射光谱的影响较大;当受力部分较小时,双折射的影响较小,此时可以把横向局部受力FBG结构看作法布里-珀罗(F-P)腔。希望这能对此类传感系统的光谱检测具有一定的参考价值。     

基于传输线理论电缆特性变化对负载影响的研究

基于长线传输理论 ,研究变频调速系统中电机端过电压的产生机理 ,分析电缆长度和特性阻抗变化对过电压的影响 .并根据阻抗匹配原则 ,设计一套安装在电机端的阻抗匹配网络 ,经实验证明能有效地抑制电机端过电压     

Discussion on coupling mechanism of asymmetric CRLH/RH TL coupler

INTRODUCTION In recent years metamaterials, more commonly referred to as left-handed materials, have stimulated great interests in the scientific and engineering field. These artificial materials, which were first theorized by Veselago (1968) and experimentally realized by Shelby et al.(2001), can exhibit specific electromag- netic properties not commonly found in nature. The approach of using transmission line theory was veri- fied to be an efficient design tool for metamaterials applica…     

Dual structure of composite right/left-handed transmission line

A dual structure of composite right/left handed （CRLH） transmission line （TL） is analyzed in which an inductance LR is in parallel with a capacitance CL and a shunt capacitance CR is in series with an inductance LL. Both the distributed and lumped cases are considered. The dispersion diagram and transmission properties of the dual CRLH TL are given and compared with those of a standard CRLH TL. Contrary to the frequency response of a standard CRLH TL, a dual CRLH TL has a left-handed （negative phase shift） band at higher frequencies and a right-handed （positive phase shift） band at lower frequencies. A novel dual-band balun is presented as an application.