共查询到19条相似文献,搜索用时 218 毫秒
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研究了线电流源平行放置在有耗异向介质层覆盖的无限长介质圆柱附近模型的电磁特性.首先,提出电磁模型并给出此电磁模型的精确解.其次,利用精确解进行数值计算,得到不同电磁参数情况下该电磁模型的近场分布图形,并通过方向性系数和归一化辐射阻抗研究其远场特性.由于有耗异向介质的负折射特性和损耗的同时作用,相比于无耗异向介质层以及有耗普通介质层,得到了有耗异向介质层覆盖普通介质圆柱模型在近场和远场特性上极为不同的电磁特性.
关键词:
线电流源
异向介质
方向性系数
辐射阻抗 相似文献
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提出一种单元电尺寸小、工作频带宽、损耗小、结构简单的异向介质设计方案,在1.7—2.7 GHz上所设计的异向介质结构单元电尺寸小于0.035,相对带宽达到45.5%,在整个工作频带上单个结构单元传输损耗小于0.75 dB.对由上述异向介质单元构成的半无限大异向介质平板的电磁波反射、透射特性进行了数值仿真分析,并提取出了电磁波在该异向介质平板中传播时的波数、相速、折射率以及该异向介质平板的有效介电常数和有效磁导率等一系列电磁特性参数,仿真与计算结果表明复波数的实部、相速以及折射率的实部在1.7—2.7 GHz的范围上为负值,并且在相同频带上,有效介电常数和有效磁导率的实部同时为负值,从而有效地验证了“后向行波效应”、“负折射效应”、“双负效应”等异向介质特有的电磁特性,对上述异向介质的存在性给予有力证明.
关键词:
异向介质
宽频带
小单元
介质参数 相似文献
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研究了THz波段强降雨环境下电磁源的辐射特性。基于通用的麦克斯韦方程组和解析分析,提出了各向异性介质中的洛仑兹规范,得到了矢量势的非齐次波动方程及矢量势的精确表达式,并证明了它们的有效性。获得了各向异性介质中电偶极子的辐射场,将各向异性介质退化为各向同性时,得到的辐射场与已有资料中的辐射场一致。基于石膏晶体和强降雨介质的各向异性参数,对电偶极子的辐射特性进行了物理模拟和分析,结果发现:介质的各向异性对其中电磁源辐射有着显著的影响,强降雨中电磁源的辐射具有较弱的各向异性。 相似文献
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通过求解沟道的二维泊松方程得到沟道表面势和沟道反型层电荷,建立了高k栅介质小尺寸绝缘体上锗(Ge OI)p型金属氧化物半导体场效应晶体管(PMOSFET)的漏源电流解析模型.模型包括了速度饱和效应、迁移率调制效应和沟长调制效应,同时考虑了栅氧化层和埋氧层与沟道界面处的界面陷阱电荷、氧化层固定电荷对漏源电流的影响.在饱和区和非饱和区,漏源电流模拟结果与实验数据符合得较好,证实了模型的正确性和实用性.利用建立的漏源电流模型模拟分析了器件主要结构和物理参数对跨导、漏导、截止频率和电压增益的影响,对Ge OI PMOSFET的设计具有一定的指导作用. 相似文献
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Q. Wu H.-L. Wang F.-Y. Meng L.-W. Li J. Wu 《Applied Physics A: Materials Science & Processing》2007,87(2):335-341
This work concentrated on an ELS (electric line source) radiating parallel to a lossless metamaterial covered infinitely long
conductor cylinder. First, the exact analytical solution of the electromagnetic model is derived. Second, the numerical results
based on the solution are given. Under different geometric and electromagnetic parameters, the patterns of the near field
are obtained; the directivity and normalized radiation resistance are presented to discuss the properties of the far field.
Because of the negative refraction of the metamaterial, it can be seen that there is a distinct “focus” in the metamaterial
layer from the near field pattern, which does not exist in conventional material layer. The presented electromagnetic model
is compared with the former, simpler model through the directivity and its validity is proven.
PACS 78.70.Gq; 81.05.Zx; 84.40.Ba 相似文献
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Hai-Long Wang Qun Wu Le-Wei Li Jian Wu 《International Journal of Infrared and Millimeter Waves》2008,29(4):373-384
The electric field properties of the electric line source radiation in the presence of a lossy metamaterial covered dielectric
cylinder are investigated. Firstly, the electromagnetic model configuration is given. The exact solution of the electromagnetic
is presented. Secondly, the near field and the far field properties are investigated according to the electromagnetic and
geometrical parameters. The different “focus” phenomenon, the directivities and the normalized radiation resistance are discussed
and important conclusions are obtained. During all the numerical computation, the lossy conventional material covered dielectric
cylinder is utilized as the reference. 相似文献
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Hai-Long Wang Qun Wu Hang Su Fan-Yi Meng Jian Wu 《International Journal of Infrared and Millimeter Waves》2008,29(2):157-166
The electric field properties of the horizontal dipole radiation in the presence of a lossless metamaterial sphere are investigated.
First, the solution of the electromagnetic field of the model could be obtained. Second, the near field properties are investigated
according to the electromagnetic and geometrical parameters. It could be seen that in the metamaterial sphere, the focusing
phenomenon is obviously observed. It is in consistent with the analysis. Throughout the article, the conventional sphere is
utilized as reference. No focus is observed in the conventional material sphere as it does not have the characteristic of
negative refraction. 相似文献
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主要围绕磁导率接近0的MNZ超材料,通过理论分析和数值模拟方法对MNZ材料的电磁特性进行了研究。针对线源置于二维MNZ材料内部的情况,通过理论详细分析了在MNZ材料和空气交界处的阻抗匹配特性和传播常数的连续性,基于有限元数值方法模拟验证了电磁场在MNZ材料边界处的等幅同相特性,从而实现了均匀平面波的传播特性。同时,考虑到将线源置于空气中有助于辐射出电磁能量,通过数值模拟分析了电磁波由空气入射到MNZ材料的电磁特性,发现在特定极化条件下,只能当电磁波波前与MNZ材料边界平行时,才能较好地实现阻抗匹配,从而基于MNZ材料实现新颖的辐射特性。 相似文献
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光学双稳态的阈值取决于非线性材料中的场局域程度, 场局域越强阈值越低. 而材料的损耗是影响场局域强弱的重要因素. 之前, 人们普遍认为, 增加损耗会削弱场局域, 不利于降低阈值. 本文研究了由磁单负材料和电单负材料组成的异质结构中光学双稳态现象, 发现随着损耗的增大, 其阈值可以呈现先降后升的非单调变化. 进一步研究表明, 异质结构界面处的电磁场强度随着损耗增大呈现先降后升的非单调变化, 即增加损耗也有可能增强场局域. 研究结果揭示了场局域程度与材料损耗之间的非单调依赖关系, 为设计开发非线性功能器件提供了新的思路. 相似文献
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A biharmonic differential equation for 3D thin microcavities with uniform thickness is investigated by use of electromagnetic theory, whose exact solution is determined to govern the electromagnetic field distribution inside the thin microcavities. The resonant field patterns of a thin microdisk and thin rectangular microcavity are obtained accordingly. The governing equation can be verified by comparing the results of the thin microdisk presented with the approximate ones in the literature. The fourth-order partial differential equation and its exact solution should be useful in possible applications of the thin microcavities for optical resonators in laser optics and optical devices. 相似文献
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数值仿真研究了一种可调谐的双开口谐振环(DSRR)超材料.在平行入射的电磁波激励下,这种DSRR单元可以在不同的频段分别表现出磁谐振和电谐振.当外加电场E与DSRR的双开口平行时,DSRR受激励得到的磁谐振和电谐振强度最大.随着DSRR超材料沿外加磁场H方向顺时针旋转,其磁谐振和电谐振频率基本保持不变,但谐振强度均发生显著下降,同时对应透射相位的突变也逐渐降低.提出的超材料调谐方法只需要简单地旋转材料,而不需要改变原有超材料单元的结构或者增加额外的激励场,极大地简化了可调谐超材料的制备及应用,在电磁开关、相位调制等方面具有潜在的应用.同时,这种简单的方法有希望应用于更高频段的超材料调谐,可以有效地拓展太赫兹频段和光频段超材料的实际应用. 相似文献