非均匀介质球颗粒的等效介电常量

从求解拉普拉斯方程的边值问题出发,讨论了非均匀介质球颗粒的等效介电常量,给出了多种介质组成的多壳层介质球颗粒的等效介电常量的一般递推公式,推导了壳层的介电常量随半径连续变化的梯度介质球的等效介电常量的微分方程．并以壳层的介电常量为幂函数为例,得到了梯度壳层介质球的等效介电常量．     

带壳介质椭球的等效介电常量

通过引入椭球坐标系,求解满足给定边界条件的拉普拉斯方程,得出了带壳介质椭球内外的电势分布,从而进一步讨论了带壳椭球的等效介电常量.     

相对介电常量实验研究

利用冰作介质，在低频范围内研究了相对介电常量随频率变化的规律。     

用晶体管开关电路测量电容和介电常量

介绍一个实用的晶体管开关电路，用它能够较准确地测定电容和介电常量。     

含有偏心球形微粒介质球的有效介电常量

对于处在均匀外电场中含有偏心球形微粒的介质球,利用分离变量法求出球内外的电场,给出了球外电偶极矩和电四极矩的近似表达式.首次引入含有偏心球形微粒介质球的有效介电常量,它不同于同心多层介质球的等效介电常量,不仅与介质球内的介质有关,而且与球外介质有关.数值结果显示了有效介电量数随偏心距和球外介质介电常量的变化情况.     

电介质的极化机制与介电常量的分析

在简介电介质极化机制的基础上,通过Lorentz振子模型及其修正,分析电介南的极化机制与介电常量,比较分析了一些电介质介常量有规律的变化,分析了一些电介质介电常量与光频介电常量相等的微观机制。     

用天平测定电介质的相对介电常量

利用分析天平，测出了带电平行板电容器两金属板间的相互吸引力F，根据F与两极板间电压U的函数关系，对测量数据进行回归计算，得出平行板电容中电介隔片的相对介电常量。     

真空介电常量和真空磁导率在高斯单位制中的数值

首先由ε 0和μ0在国际单位制中的数值得出其在高斯单位中的数值, 然后利用之, 把电磁学公式由S I制 化到G a u s s制, 并利用它解释了存在真空极化的合理性, 及“ 真空磁化”的存在     

频率相关材料的计算模型分析

系统地介绍了Debye、Drude、Lorentz模型相对介电常量的推导过程,并给出了其相应结果;再用有损耗的Drude模型讨论了当前引起广泛关注的左手介质的性质;最后通过推导和举例,进一步揭示了各种模型在实际研究中的重要作用.     

具有复介电常量一维光子晶体的特性研究

利用传输矩阵法计算了一维光子晶体的能带结构和光传输特性,重点讨论了介电常量的虚部为负值时对传输特性的影响。当在介质中掺入具有增益特性的介质时,靠近光子带隙边缘就会出现较强的受激辐射放大。同时,光子晶体的长度和介电常量虚部的大小都会影响晶体的受激辐射。随着虚部数值的增加,受激增强并不是单调递增,而是存在一极值点。     

Rain induced attenuation of millimeter waves radio link in Indian continent

The performance and reliability of millimeter wave radio link is degraded mainly by rain. In the present paper the aspect of rain induced attenuation with respect to raindrop is described. How the microstructure details of rain are necessary for estimating the rain induced attenuation in millimeter wave region are explained on the basis of the rain data for different stations of India.     

System Identification Models of the Equivalent Permittivity for Rain Medium

The dielectric constant for rain medium is investigated by utilizing the system identification method. The rain rate model and frequency model of permittivity in millimeter waves band for rain medium are presented. The results obtained with models are in very good agreement with references in calculating the attenuation of electromagnetic waves induced by rain, which Shows that the obtained models are valid and practicable. The cross-polar discrimination gotten with rain rate model is in agreement with references.     

Measurement of Low-Loss Dielectric Materials Using Dielectric Rod Resonator

To obtain the complex permittivity of low-loss dielectric materials at 60 GHz, a measurement method is developed. Using a dielectric rod resonator excited by a dielectric waveguide, effective conductivity of conducting plates for short circuiting the resonator is determined. The complex permittivity of the dielectric rod is determined by the resonant frequency and unloaded quality factor of the TE_0m1-mode resonator. Moreover, the complex permittivity of single crystal sapphire, polycrystalline ceramics, and cordierite has been investigated in virtue of numerical simulation. For all the measured specimens in this study, the proposed method is seen to provide much better accuracy for values. This work was supported in part by the National Nature Science Foundation of China, under Grant NSFC 60671009.     

A Method for Determining the Dielectric Constant of Microwave PCB Substrates

This paper presents a simple method for determining the dielectric constant of microwave PCB substrates. In the presented method, a bandpass microstrip filter designed on the PCB substrate with a user-predicted dielectric constant value is implemented for a given center frequency. The simulation results of the designed bandpass filter are obtained by the help of microwave design software; XFDTD?. Experimental results regarding the filter frequency characteristic are accomplished by means of a vector network analyzer. The simulation results of the designed filter are modified to overlap with the experimental ones by varying the dielectric constant value. When the simulation and experimental results are overlapped, the value of dielectric constant is accurately selected. In order to illustrate the validity of proposed method, the dielectric constant values of flame resistant-4 (FR4) substrates are acquired at IEEE 802.11b/g and IEEE 802.11a wireless local area network (WLAN) application frequencies. The results obtained by using the presented method agree with the previous studies in the literature.     

外围介质介电常数对金纳米棒光学性质影响的数值模拟

采用电化学方法制备出悬浮胶体金纳米棒。在室温下测得其紫外-可见吸收光谱和荧光发射光谱。结合准静电场理论与散射理论对金纳米棒的光学特性进行了数值模拟。计算结果表明,由于金纳米棒形状的各向异性,吸收截面与散射截面均出现两个共振峰,分别对应于横截方向与长轴方向的表面等离子共振。对于几何形状一定的金纳米棒,在外围介质介电常数从1.5增加到2.5的过程中,两个共振吸收峰均增强并非线性红移。然而对于散射光谱,短波方向的共振峰线性红移,强度变化微弱;长波方向的共振峰减弱并非线性红移。     

Attenuation of Centimetre, Millimetre and Sub-Millimetre Waves Due to Rain Over Tropical Indian Stations

The results on attenuation of the radio wave due to rain at frequencies lying in the centimetre, millimetre and submillimetre wave bands for different rain rates over three Indian tropical stations are presented in this paper. The study is possible due to the availability of the rainfall rates measured by rapid response rain gauges and rain height over these stations. The results on attenuation were deduced by taking both 0° C isotherm height and effective height. The Stutzman and Dishman model with -value of 0.033 which is found suitable for the estimation of rain attenuation over the Indian stations has been critically examined in comparison with the attenuations deduced from CCIR (presently known as ITU-R) method.     

Rain Rate Statistics and Fade Distribution of Millimeter Waves in Indian Continents

For any communication service operating in the Microwave/ Millimeter wave region, statistical information characterising the attenuation due to rain along satellite slant path would be required for the design of satellite communication links and for the broadcasting network above 20 Ghz. It is necessary to have a prior knowledge of the probability of exceeding different levels of rain attenuation in order to design appropriate fade margins into systems and establishing estimates of the year to year variability of rain fade margin for particular geographic regions of India so that the communication system reflects the extremes of these variabilities. Direct measurement of beacon signals from geostationary satellites have been a mean to determine the above information and experiments can be pursued with satellite such as INSAT. [1]Attenuatiuon of Millimeter Waves by rainfall restricts the path length of a communication system. A knowledge of the rain attenuation at such frequencies is therefore desirable in designing a reliable communication system. Signal level fading over line-of-sight links strongly depends on the hop length, frequency and climate. For short hops, the probability of occurance of deep fades becomes diminishingly small. However, since an extended hop length is possible for regions with little rain activity, clear weather fading can affect the link reliability in a similar way ti a rain.[2]     

聚合物及其混合物的太赫兹介电性质测定与分析方法

聚合物材料因其对太赫兹波的高透过率以及良好的塑形能力在太赫兹研究中扮演了重要的角色,由于材料的介电特性直接关系着折射率、极化率等重要性质,不同的应用场合通常需要材料呈现出特殊的太赫兹介电响应,一方面可以选取不同的聚合物材料,另一方面可以通过多种聚合物的混合实现材料介电性质的调制。聚合物材料合理的选取和设计建立在材料太赫兹介电精确表征之上,然而利用太赫兹时域光谱系统(THz-TDS)对聚合物材料进行透射式太赫兹介电表征时,材料内部空气孔隙的存在会影响表征结果的复现性,同时也会影响共混聚合物介电性质的分析和预测。因此以Landau, Lifshitz, Looyenga(LLL)模型为基础提出了考虑空气影响的介电分析模型,并选取了在太赫兹研究中广泛使用的聚合物材料聚乙烯(PE)和聚四氟乙烯(PTFE)对模型的有效性和稳定性加以验证,展开了两种材料单质和混合物两方面的介电分析。在太赫兹波透射样品之后的相位变化信息中提取出样品的介电常数,同一种物质制备的样片间太赫兹介电谱存在明显差异,使用包含气隙影响的LLL模型处理实验数据后,样品介电常数中空气的介电影响被移除,从而得到了两种材料的本征介电常数,在此基础上,使用测得的本征介电常数和混合物样品中两种材料的体积占比信息代入包含气隙影响的LLL模型计算得到了不同配比混合物的太赫兹介电常数的模拟值,并与THz-TDS实验获取的实验值进行了对比。利用所提出的有效介质模型,聚乙烯和聚四氟乙烯在10～40 cm-1波段内移除空气影响后的平均介电常数为2.315±0.003（±0.13%）和2.109±0.003（±0.14%）,在不同重量、不同厚度的单组份样品间模型测定的聚合物介电常数保持了良好的重复性,在对混合物的太赫兹介电性质测定与分析中,利用模型计算的混合物介电常数模拟值与THz-TDS测定的介电常数实验值保持了高度线性相关,其相关系数为0.964 3,全局相对误差为1.08%,体现了模型的可靠性。提出的介电分析模型可以扩展到更多的高分子材料单质及其混合物的太赫兹介电性质表征中,对太赫兹波段的共混聚合物材料设计具有参考价值。     

金属介电常数的色散模型对光学Tamm态的影响

比较银介电常数三种色散模型对光学Tamm态的影响,根据三种色散模型的复折射率随波长的变化研究银-光子晶体-银结构TE波和TM波的光学Tamm 态随入射角、银层厚度及周期数的变化.得出：三种色散模型下银-光子晶体-银结构中都会出现两个光学Tamm 态（OTS1和OTS2）.三种色散模型下的光学Tamm 态的波长随入射角、银层厚度及周期数的变化规律一致.但是光学Tamm 态的透射峰值随入射角、银层厚度及周期数的变化规律不一致.Drude-Lorentz模型和Lorentz模型能够描述银的特征,而Drude模型不能.     

Analysis of Frequency Selective Surfaces with Metallic and Dielectric Losses at Millimeter Wave Range

In this paper, a theoretical analysis of scattering from a doubly frequency selective surfaces (FSS) with dielectric and metallic losses in the millimeter wave range is presented. The theoretical analysis involves the solution of the electric field integral equation relating the induced current in the FSS in the presence of anisotropic dielectric layers. The method of moment is employed to obtain numerical results. The frequency selective surface structure considered is composed by conducting patch elements sandwiched between two anisotropic dielectric layers. Three different anisotropic materials are considered: Epsilam-10, Alumina, and Sapphire. The sapphire presents low losses when compared with the other two dielectric materials. The most common metals, as copper and aluminum, are considered in this analysis. None significant metallic losses were observed for any considered metal. Numerical results are presented for the scattering characteristics and for dielectric and metallic losses parameters.