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1.
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… 相似文献
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INTRODUCTION Veselago (1968) theoretically analyzed the wave propagation in a left-handed (LH) material which has simultaneously a negative magnetic permeability and a negative electric permittivity. The electric field, the magnetic field, and the wave vector of an electro-magnetic wave propagating in such a material obey the left-hand rule (instead of the right-hand rule for usual materials). Such an LH material was first real-ized in 2001 in microwave region with an array of metallic … 相似文献
3.
HU Xin ZHANG Pu HE Sailing 《浙江大学学报(A卷英文版)》2006,7(10):1777-1780
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. 相似文献
4.
INTRODUCTION Wave propagation in a material with negative magnetic permeability and negative electric permit- tivity was first theoretically analyzed by Veselago (1968). In such a left-handed material (LHM), the electric field E, the magnetic field H and the wave vector k of electromagnetic wave propagation obey the left-hand rule (instead of the right-hand rule for usual materials). After Smith et al.(2000) demon- strated simultaneously negative permeability and permittivity, using cop… 相似文献
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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… 相似文献
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INTRODUCTION Left-handed materials (LHMs) are characterized by simultaneously negative permittivity and perme- ability. It was first investigated theoretically by Ve- selago (1968). The experimental realization of LHM with resonance structures was demonstrated by Smith et al.(2000). Since then, LHM has gained significant interest and started to be integrated into novel mi- crowave and optical applications. The transmis- sion-line (TL) approach was recently proposed to realize LHMs … 相似文献
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Broadband phase shifters are mostly proposed and fabricated based on the scheme proposed by Shiffman, which uses a coupled line with far ends connected together and a uniform transmission line to give a differential phase shift. Based on the unique dispersion property of the composite right/left-handed (CRLH) metamaterial structure, a new configuration is presented in this paper for fabricating the broadband differential phase shifter, which employs a novel CRLH metamaterial structure as one of the differential phase-shift arms, instead of the conventional coupled line. The new circuit can achieve a phase shift of 90° in an operational bandwidth as broad as one octave and its phase deviations are quite small. An original design of the novel broadband phase shifter is presented, in which the artificial CRLH structure was implemented by microstrip quasi-lumped elements. Both the simulated and measured results of the 90° broadband differential phase shifter are presented. 相似文献
8.
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. 相似文献
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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. 相似文献
10.
Combining the modified Bethe small holes coupling theory with McDonald thickness theory and field averaging correction factor,
it is accurate to design the weak coupling waveguide directional coupler. While the coupling is tight, the decrease of the
field strength in the main waveguide caused by aperture should not be neglected. For a −6 dB directional coupler is described
in this article, the theoretical value of coupling is good agree to the simulation value, by simulated and optimized with
the professional software computer simulation technology (CST). In the designed waveband, the error of coupling between theoretical
value and simulating one is less than 0.25 dB. The error of coupling between simulation value and designed value is less than
0.5 dB. To improve the isolation, some spaces between two adjacent holes are turned from the traditional ? centre guided wavelength.
The performance of isolation has 5 dB improvement, and length of the coupling area is only 51.06 mm. 相似文献
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INTRODUCTION Left-handed materials (LHMs) with negative permittivity and negative permeability, first theo- retically investigated by Veselago (1968), have at- tracted much interest in the past few years (Smith et al., 2000; Pendry, 2000). Such materials were first implemented using a structure which combined pe- riodic arrays of metallic lines and split ring resonators (SRRs) (Shelby et al., 2001). Since then much work has been dedicated to fabricating such materials. These new artif… 相似文献
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贾振安 《陕西理工学院学报(社会科学版)》1998,(3)
用加电场两步离子交换工艺对掩埋式自聚焦光波导定向耦合器进行了研究和制作,制成了1对1定向耦合器样品,拍摄了样品耦合传输的端面显微照片,研究了耦合光能量随耦合长度变化的特性． 相似文献
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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。 相似文献
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借助于数值分析软件MATLAB,利用传输线理论对二平行印制线间的串扰耦合进行分析,得出耦合响应与传输线参数的定量关系,给出电子电路设计中PCB印制线布设的原则. 相似文献
16.
A new approach to the design of the optical fiber direction coupler by using neural network is proposed. To train the artificial neural network, the coupling length is defined as the input sample, and the coupling ratio is defined as the output sample. Compared with the numerical value calculation of the theoretical formula, the error of the neural network model output is 1% less. Then, through the model, to design a broadband or a single wavelength optical fiber direction coupler becomes easy. The method is proved to be reliable, accurate and time-saving. So it is promising in the field of both investigation and application. 相似文献
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针对广泛关注的左手材料(负折射率媒质),对电磁波穿过左手材料(Left-handedm aterial)构成的平行板时的传播特性做了理论分析;采用FDTD方法对正弦电磁波穿过了LHM的平行板的传播过程进行了数值建模,数值模拟的结果证明了正弦电磁波在穿过平板状的左手材料,会有类似一般凸透镜的聚光效果,以及负折射特性,为LHM的广泛应用提供了理论基础. 相似文献
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研究了光脉冲通过光子晶体线缺陷波导的透射特性.分析发现光子晶体线缺陷波导的透射行为与波导的几何尺寸有关.通过调制波导的几何结构可以获得较平坦的透射谱.另外发现耦合线缺陷所选择的点缺陷是影响线缺陷波导透射特性的重要因素,通过调节点缺陷的尺寸,缺陷间可以很完美的耦合并获得超平坦的杂质带.该分析结果为光子晶体线缺陷波导的设计提供重要参考. 相似文献
19.
光电耦合器及其应用 总被引：2，自引：0，他引：2
唐红 《贵阳学院学报(自然科学版)》2006,1(4):7-10
半导体光电耦合器现已发展成为一类特殊的半导体隔离器件.它体积小、寿命长、无触点、抗干扰、能隔离,并具有单向信号传输等特点.本文介绍了光电耦合器的特点、典型结构及应用,以及简易测试方法. 相似文献
20.
XIAOYan－ping WUYa－ming 《上海大学学报(英文版)》2001,5(1):48-52
Narrow bandwidth is a crocial factor in a high-performance wavelength-selective device(WSD).There are many different expressions to estimate bandwidths of many different WSDs.In this paper,we derive an important rule that the differential time delay between two coupling modes is the most important factor deciding the wavelength channel bandwidth for several different WSDs.This rule reveals that larger differential time delay between two coupling modes results in higher discrimination level of the operating wavelength.Based on the rule .a novel design of wavelength-selective coupler that has a bandwidth narrower than normal couplers is presented. 相似文献