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INTRODUCTIONInvestigationofphotonicbandgap(PBG)materialsiscurrentlyoneofthemostactivefron-tiersinengineeringandphysics.PBGmaterialshaverecentlyemergedasanewmultidisciplinaryfieldofstudy(Kesleretal.,1996;Yablonovitch,1994;SimovskiandHe,2001).APBGstructurecanhaveabandgapwithinwhichelectromagnetic(EM)wavepropagationispreventedinalldirec-tions(Joannopoulosetal.,1997;Ozbayetal.,1994).Foratwo-dimensionalPBGmaterial,thepropagationofanEMwavewithinitsbandgapispreventedinalldirectionswithin… 相似文献
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ZHU Fang-ming HU Jun 《浙江大学学报(A卷英文版)》2007,8(2):192-196
INTRODUCTION Metamaterials are periodic metallic structures exhibiting unique properties not existing in natural materials. They are also called backward wave mate- rials, double negative materials, or left-handed mate- rials (LHM) in particular, in which the vectors E, H and k form a left-handed system. Since the idea pro- posed by Veselago (1968), metamaterials have at- tracted great interest in the last years (Smith et al., 2000; Pendry, 2000; Smith and Kroll, 2000; Shelby et al., … 相似文献
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A new patch antenna with metamaterial cover 总被引：6，自引：0，他引：6
INTRODUCTION Investigation of metamaterials is currently one of the most active frontiers in engineering and physics. Metamaterials are also called backward-wave mate- rials, double-negative materials, or left-handed mate- rials. Left-handed materials were proposed by Vese- lago (1968). The applications of metamaterials are widely spread in many fields (Pendry, 2000; Grbic and Eleftheriades, 2003; Foteinopoulou et al., 2003), such as imaging apparatus, planar light wave circuits, optica… 相似文献
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用于通信的超宽带印刷天线 总被引：1，自引：1，他引：1
1IntroductionUltra-wideband(UWB)microwave antennas are ofinterest for a variety of applications such as electroniccountermeasure,transient radars,mine detection,andunexploded ordnance(UXO)location and identifica-tion.In the early2002,the release of the UWB forcommercial communications by the Federal Communi-cation Commission(FCC,USA)sparked renewed in-terest in the subject of UWB antennas.Conventional UWB antennas such as log-periodic orspiral antennas exhibit good UWB characteristi… 相似文献
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为了有效地计算非矩形光子晶体带隙结构,将非正交坐标系用于时域有限差分(FDTD)方法中,在非正交坐标系下离散麦克斯韦方程组,重新推导了FDTD递推公式。将本征色散变量表达方法应用到非正交坐标系,提高了计算的准确性。用这种非正交的FDTD方法研究了非矩形光子晶体横磁场模的带隙结构。数值模拟结果验证了上述计算方法的有效性。 相似文献
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HUANG Biao YAN Guo-zheng LI Qian-ru 《浙江大学学报(A卷英文版)》2007,8(10):1560-1567
Antenna is very crucial to radiotelemetry capsules which can measure the physiological parameters of the gastroin- testinal (GI) tract. The objective of this paper is to design a novel spiral slots microstrip patch antenna for the radiotelemetry capsules communicating with external recorder at 915 MHz located in ISM (Industry, Science, and Medical) bands. The microstrip patch antenna is designed and evaluated using the finite-difference time-domain (FDTD) method. Return loss characteristics and the effect of the human body on resonant frequency are analyzed, and the performances of radiation patterns at different positions of the human alimentary tract are also estimated. Finally, specific absorption rate (SAR) computations are performed, and the peak 1-g and 10-g SAR values are calculated. According to the peak SAR values, the maximum delivered power for the designed antenna was found so that the SAR values of the antenna satisfy the ANSI (American National Standards Institute) limitations. 相似文献
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为提高圆形微带贴片天线的性能,提出将一种新型圆柱电磁带隙(EBG)结构应用于天线中,这种柱形EBG基片由两种不同周期单元组成,分别是金属环和接地过孔,形成一种辐射状的圆形周期结构.首先设计了一个圆形微带贴片天线,然后应用电磁仿真软件HFSS对两种周期结构的参数进行了优化分析,最后对加载EBG结构前后微带贴片天线的辐射方向图和回波损耗进行了比较.结果表明,在阻抗匹配良好的前提下,天线增益增强了4.6dB左右,提高了天线的应用性. 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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把时域有限差分方法用于二维正方介质柱组成光子晶体传输函数理论研究,计算了若干情况下二维光子晶体的透射率即光传输函数随频率的变化。计算结果表明:对于一定的入射方向,某些频率的光不能在光子晶体中传播即出现所谓的禁带,禁带的宽度、频率范围与晶格结构、柱体截面大小及放置方位有关。 相似文献
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Novel circularly-polarized ceramic dielectric resonator antenna excited by a corner-cut square patch
A ceramic dielectric resonator antenna excited by a corner-cut square patch for the circularly-polarized operation is introduced.
The effect of patch size and cut size is investigated, showing that the resonant frequency of the antenna can be changed by
simply changing the patch size. The reflection, axial ratio, and radiation characteristics of the antenna are found. Measurements
were carried out to verify the design. The antenna is compact in structure, which is attractive in the application as the
satellite communication terminals. 相似文献
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为了适应卫星通信系统终端的需求,设计了一种三频段天线,辐射贴片的基本形状为四周圆角的矩形,在贴片上分别开T形槽和L形槽,使天线产生3个工作频点。通过对辐射贴片的电流分布和槽形结构进行分析,发现开槽可使电流路径增加,在所需的频段范围内能有效降低回波损耗;同时发现,减小天线的接地面宽度,可减小天线尺寸,从而提高天线的辐射效率。实测结果表明该天线能满足设计要求。 相似文献
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It is a challenge for passive RFID tags to be mounted on the surface of metal because the parameters of tag antennas, such as the impedance matching, the radiation efficiency and the radiation pattern, are seriously affected by the metallic surface. This paper presents the characteristics of the dipole-like antennas of ultra high frequency （UHF） radio frequency identification （RFID） tags that are placed close to metallic surfaces. The finite element method （FEM） and method of moment （MoM） were used to simulate the changes of the antenna parameters near the metallic surface. Two typical dipole-like antennas close to the metallic surface, a closed loop antenna and a loaded meander antenna, were modeled, and the performance was evaluated. Experiment was carried out and the results were in good agreement with the simulation, showing that a distance of 0.05λ-0.1λ （λ is the free space wavelength） from the metallic surface could make the dipole-like UHF RFID tag performance be acceptable. 相似文献
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为了实现双频天线的小型化,对平面倒F形天线给出一种改进,在辐射贴片上开一个T形槽．再将它的尾部向内折叠。通过与L形开槽的倒F形天线相比表明：改进后天线的结构更加紧凑,尺寸减小30％以上,且在给定的工作频段具有良好的辐射特性。 相似文献
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THz频域层状一维光子晶体光纤的设计 总被引：1，自引：0，他引：1
黄艳月 《赣南师范学院学报》2008,29(3):61-65
针对传统金属微波波导和介质光波导难以解决飞秒激光脉冲作用于光电导天线或光整流晶体产生的0.1-4THz脉冲辐射传输中的群速色散问题,光子晶体光纤在色散设计方面具有很强优势.本文利用光在多层介质中传输的传输矩阵法对层状一维光子晶体光纤进行数值计算,并通过对THz频域材料特性的研究,设计出适合于传输0.1-1THz频段的层状一维光子晶体光纤. 相似文献
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文章通过时域有限差分(Finite-Difference Time-Domain,FDTD)方法分析3维(three dimensional)微带天线的散射参数和远场主极化方向图和交叉极化方向图,仿真结果(simulation results)与文献及ansoft软件的仿真结果进行了对比,证实了采用2阶Mur吸收边界条件的FDTD算法的有效性. 相似文献
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阐述了光子带隙的基本概念,以及微结构光纤中存在光子带隙的理论基础．用基于透射谱的方法测试了近红外波段800-3200nm范围内的三种微结构光纤,从透射谱图中发现有多条透射带,验证了光子带隙的存在． 相似文献
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温煜东 《晋城职业技术学院学报》2013,(6):59-61
本文设计了一种应用于无线局域网的电磁带隙结构(EBG)的微带天线。通过在微带贴片天线的辐射单元周围加载蘑菇型EBG结构,使得天线的带宽、增益性能得到了显著改善。仿真结果表明,与普通贴片天线相比,加载EBG结构时天线带宽增加了6%,主辐射方向上增益增大了1.98dB。 相似文献
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一种平面倒F型三频手机天线设计 总被引：1，自引：0，他引：1
为了实现手机内置天线的小型化和多频段,提出了一种平面倒置F型三频段天线.结构采用空间折叠实现了小型化,开双L型槽实现了多频段工作.测试结果表明,其尺寸和频率都能满足现代无线通信系统对移动终端的要求. 相似文献