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1.
Weihai Fang Shanjia Xu 《International Journal of Infrared and Millimeter Waves》2006,27(12):1683-1694
The effects of left-handed materials (LHM) on frequency selective reflection and transmission characteristics of dielectric
periodic structures are carefully investigated using a method which combines the multimode network theory with the rigorous
mode matching method. In addition, the effects of LHM dielectric loss on the selective properties are also given. It has been
shown that the selective behavior of periodic structures can be modified by adding LHM layers above and below the periodic
layer.
Supported by the National Natural Science Foundation of China (No. 60171037) (No. 60371010) and (No. 63531020) 相似文献
2.
Scattering Characteristics of Dielectric Periodic Structure Composed of Left-handed Materials with Arbitrary Oblique Incidence 总被引:1,自引:0,他引:1
Weihai Fang Shanjia Xu 《International Journal of Infrared and Millimeter Waves》2008,29(11):1060-1069
Scattering characteristics of monolayer and multilayer dielectric periodic structure composed of left-handed materials (LH-DPS)
with plane wave arbitrary oblique incidence are carefully analyzed using a method which combines multimode network theory
with the rigorous mode matching method. Our analysis results reveal that the arbitrary oblique incident angles and relative
position between different LH-DPS have great effects to the scattering characteristics of LH-DPS which different from the
situation of dielectric periodic structure composed of right-handed materials (RH-DPS). The reasons why the reflection characteristics
of the LH-DPS are totally different from those of the RH-DPS with arbitrary oblique incidence are also given. The present
quantitive investigation provides guidelines for the design of the monolayer and multilayer dielectric frequency selective
surfaces for millimeter wave applications. 相似文献
3.
A new dielectric slab waveguide with a left-handed material (LHM) cover and substrate is proposed. The dispersion relations
and normalized effective thickness of the asymmetric LHM slab waveguide are investigated, in view of the normalized parameters.
A number of unusual properties are found, for example, the fundamental and first-order modes do not exist and higher-order
modes have double degeneracy. The propagation modes are absent at the low normalized frequency, and the cutoff frequencies
of some LHM slab waveguide modes decrease with increase in the asymmetry measure. Unlike traditional slab waveguides, the
V –H curves of the LHM slab waveguides are in one-to-one correspondence. Both TE and TM modes are discussed; in addition, the
dispersion relations and normalized effective thicknesses of the TM modes are discussed in detail, when the difference in
refractive indices of the film and the substrate is small. The results show that the region of mode coexistence taking place
near the cutoff frequency becomes narrower with increase in the difference in refractive indices of the film and the substrate.
The influence of this difference on the normalized effective thickness curves is different, and becomes smaller and smaller
with increase in the value of the asymmetry measure, if different values of the refractive indices are employed. 相似文献
4.
左手介质矩形波导导模和表面模的场分布 总被引:2,自引:0,他引:2
从麦克斯韦方程组出发,结合电磁场的边界条件,推导出介质矩形波导导模的一般色散方程.对普通介质矩形波导和左手介质矩形波导的导模场分布分别进行了数值模拟.通过对比两种介质矩形波导的导模场分布的模拟结果,发现左手介质矩形波导Ex22模的场分布比普通介质波导Ex00模的场更集中在波导中部.同时,根据处理普通介质矩形波导的Marcatili方法.类比得到左手介质矩形波导表面模的色散方程,并数值模拟了低阶模的场分布,结果表明,能量主要集中在波导的四个角区以及波导的边缘. 相似文献
5.
为了满足现代通信设备多频带及集成化要求,基于耦合机理和谐振机理,在实心半波壁雷达罩和A 夹层雷达罩等效平板基底上设计了一种由容性表面(内嵌谐振单元)-感性表面-容性表面(内嵌谐振单元)-等效基底级联而成的Ku/Ka波段双通带频率选择表面结构. 根据FSS的物理结构建立了等效电路模型,分析了滤波机理,利用全波分析软件计算了两种FSS雷达罩的传输特性. 该结构基于容性表面与感性表面的耦合作用在Ku波段形成具有微型化特性的第一通带,基于两个容性表面内嵌的方环单元谐振在Ka波段形成第二通带,两通带透过率分别为89%,94.7%(实心半波壁FSS雷达罩)、88.2%/93.7%(A夹层FSS雷达罩),在0°–45°扫描范围内,两通带传输特性稳定. 在半波壁雷达罩的等效平板上制作了Ku/Ka双通带实验样件,利用自由空间法测试其传输特性,在制作误差允许的范围内,测试结果与仿真结果基本一致. 为研究通带间隔较宽的多频FSS 提供了理论和实验依据.
关键词:
雷达罩
频率选择表面(FSS)
双通带 相似文献
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7.
Design of a tunable frequency selective surface absorber as a loaded receiving antenna array 下载免费PDF全文
An effective approach to designing a tunable electromagnetic absorber is presented and experimentally verified; it is based on an idea that an existing frequency selective surface (FSS) absorber is regarded as a loaded receiving antenna array. The existing absorber is effectively simplified by withdrawing half of the loaded resistors; a more compact one is obtained when lumped capacitors are introduced. Building on this, a varactor-tunable absorber with a proper bias network is proposed. Numerical simulations of one tunable absorber with 1.6 mm in thickness show that a wide tuning range from 3.05 GHz to 1.96 GHz is achieved by changing the capacitance of the loaded varactor from 0.5 pF to 5.0 pF. An experiment is carried out using a rectangular waveguide measurement setup and excellent agreement between the simulated and measured results is demonstrated. 相似文献
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用新局域模型计算高Z靶的溅射产额 总被引:1,自引:0,他引:1
用ACAT模拟程序计算了不同离子碰撞在单原子材料上的溅射产额。计算中采用山村等人提出的包括壳效应的新电子能量损失局域模型 ,原子间作用势使用Moli啨re势?扑愕玫降慕峁胧笛槭莺蜕酱宓鹊木楣浇斜冉?,符合得很好 相似文献
11.
周炎如 《光谱学与光谱分析》1992,12(6):33-36
应用光谱减(Subtract)程序,将混合化合物中的“标志谱带”进行光谱自身加减,从而使不等厚度涂片样调整到等厚度。然后用Specfit程序定量,其均方误差在0.0011~0.0193之间。 相似文献
12.
In this work,we propose an all-dielectric frequency selective surface(FSS) composed of periodically placed highpermittivity dielectric resonators and a three-dimensional(3D) printed supporter.Mie resonances in the dielectric resonators offer strong electric and magnetic dipoles,quadrupoles,and higher order terms.The re-radiated electric and magnetic fields by these multipoles interact with the incident fields,which leads to total reflection or total transmission in some special frequency bands.The measured results of the fabricated FSS demonstrate a stopband fractional bandwidth(FBW)of 22.2%,which is consistent with the simulated result. 相似文献
13.
The TE/TM polarization conversion characteristics of dielectric grating composed of left-handed materials for the case of
plane wave oblique incidence are carefully investigated by a method which combines the multimode network theory with the rigorous
mode matching method. It is indicated that complete polarization conversion between TE and TM modes can be realized using
left-handed gratings. This can hardly achieve in the conventional right-handed gratings. Comparisons of polarization conversion
properties between right-handed gratings and left-handed gratings are given with physical explanations. This unique merit
of left-handed periodic structure is of important significance for accurate design of new millimeter wave TE/TM polarization
converters. 相似文献
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In a planar lens made of left-handed material (LHM), the rays converge to a focal point in the material and once again in
free space. The problems exhibited by the planar lens are its great thickness, the long optical path length, and energy concentration
in the LHM. We examine a bowl-shaped LHM lens with an index n = −1. In this lens, the back is a concave hemispherical surface and the rays never converge in the LHM, but in free space
only. We also designed a quantized bowl-shaped LHM lens composed of multiple layers of thin LHM plates of uniform thickness.
A bowl-shaped LHM lens quantized with more than 4 bits has a lens function similar to that of a smooth curved lens. The bowl-shaped
lens is characterized by its thinness, its short optical path length, and the absence of energy concentration in the LHM.
Furthermore, the quantized bowl-shaped LHM lens can be fabricated. Wave propagation through these lenses is numerically simulated
using the finite difference time domain (FDTD) method. 相似文献
16.
利用分形单元的自相似性将分形结构应用于频率选择表面(FSS)领域使单屏FSS具有多频谐振的特性,在各波段实现简易、多频带通滤波器的设计.以易加工的十字单元为例,经过递归、迭代产生二阶十字分形单元,给出描述单元几何分布的公式;应用周期矩量法结合Floquet定理及阻抗边界条件得到描述FSS表面电流分布的电场积分方程,对FSS传输特性规律进行数值分析,采用遗传算法对分形单元参数进行全局优化得到了在9.2 GHz和29.4 GHz谐振的单屏FSS设计;最后采用成熟的镀膜、光刻工艺制备十字分形FSS样件并在微波暗
关键词:
频率选择表面(FSS)
分形单元
多频段
周期矩量法(PMoM) 相似文献
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Microwave and optical properties of lithium niobate electrooptic modulators are investigated in this paper. The effect of simultaneous matching of optical and microwave velocities and impedance matching, conductor loss, dielectric loss on the optical bandwidth of an ultra-high-speed lithium niobate modulator are presented here. The metal electrode design, buffer thickness, ridge depth, and the gap between electrodes at different operating frequencies on device performance are thoroughly investigated by using the finite element method. 相似文献
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