Optimizing VLSI interconnect model for SPICE simulation

The importance of matching the frequency range for electromagnetic analysis and circuit simulation of VLSI interconnects is discussed in this paper. The electromagnetic analysis utilizes Helmholtz equation to calculate eddy-current loss and dielectric loss. Modeling is based on assembling filters with high cutoff frequencies and small numbers of components. The performance of a gate-array interconnect at different clock frequencies is analyzed.     

基于软件无线电的灾害救援生命探测方法研究

利用电磁波进行灾害救援生命探测的过程中,探测深度与电磁波工作的频点有直接关系。不同频率的电磁波在同种介质中的传播速度不同,频率越大折射率越大,速度越小,因此在不同介质的界面上电磁波的衰减率有明显变化。但现有的地质(探地)雷达由于其硬件电路的关系,其电磁波的工作频率点相对不变,致使只能得到在单一频率下的探测信息,这样会导致探测信息不够完整。同时,在灾害救援现场由于大量使用无线通信设备,造成无线频段之间的干扰,得到的探测信息不可靠。现在用软件无线电在多频带/多模式/多功能等优势,为灾害生命救援探测提供了一种新的方法。     

周期线性变化光子晶体用于色散补偿的研究

文章研究了周期线性变化的一维光子晶体的色散补偿特性.根据周期性介质中电磁场在界面处的传递规律,利用传输矩阵方法分析了不同频率的光波在周期线性变化的一维光子晶体中的反射特性,结果表明这种光子晶体对于不同频率的光波成分具有不同的延时,利用这种延时特性,可以制作用于密集波分复用(DWDM)系统的色散补偿器件.     

Frequency-Dependent Absorption of Electromagnetic Energy in Biological Tissue

The frequency-dependent absorption of electromagnetic energy in biological tissue is illustrated by use of the Debye equations, model calculations for different irradiation conditions, and measured electrical properties (conductivity and permittivity) of different tissues. Four separate irradiation conditions are treated for calculating the power absorbed. in a given tissue when it forms a flat interface or is surrounded by another tissue. The calculations show that the greatest differential absorption occurs at frequencies between the dominant relaxation frequencies in the two tissues. From rat mammary gland tumor data, the calculations show an optimum frequency range of about 100-500 MHz for microwave hyperthermia treatment of at least these types of tumor.     

一种二维金属电磁带隙结构的电磁传输特性

采用时域有限差分法与Floquet定理相结合，对由正方形金属柱构成的二维电磁带隙结构的传输特性进行了分析和计算，得到了不同频率的平面电磁波在不同角度入射时，该结构的传输参数及电磁特性。通过改变金属方柱的边长和间距，得到了电磁带隙结构的阻带中心频率的变化规律，进而得到了拟合公式，该公式计算结果与仿真结果间最大误差不超过2％，具有较好的可靠性和较高精度，可用于EBG结构的应用研究。     

Attenuation predictions at extremely low frequencies formeasurement-while-drilling electromagnetic telemetry system

Extremely low frequencies (ELFs) are employed to transmit data from underground to the ground surface in the measurement-while-drilling electromagnetic (MWD-EM) telemetry system. Based on electromagnetic field theory, the present work is aimed at predicting the receivability of the signals at the surface. A unified analytic method that is suitable for vertical, directional, or horizontal wells is presented. Attenuation properties are examined for various parameters, including the Earth's conductivity, operating frequency and the length of the drill string. The frequency dependence of the receivability in reference to a noise level is illustrated for different depths of well and different cases. It is also demonstrated that the electric field distributions at the surface have the same features for the three types of well, and that the measurements should be carried out near the well heads for any type of well. A scale model experiment is made to test the authors' theoretical results. The measured data and the computed results are comparable     

Detection, mixing, and frequency multiplication of terahertzradiation by two-dimensional electronic fluid

We show that a short channel High Electron Mobility Transistor (HEMT) has a resonance response to electromagnetic radiation at the plasma oscillation frequencies of the two dimensional electrons in the device. This response can be used for new types of detectors, mixers, and multipliers. These devices should operate at much higher frequencies than conventional, transit-time limited devices, since the plasma waves propagate much faster than electrons. The responsivities of such devices may greatly exceed the responsivities of Schottky diodes currently used as detectors and mixers in the terahertz range. A long channel HEMT has a nonresonant response to electromagnetic radiation and can be used as a broadband detector for frequencies up to several tens of terahertz     

Electromagnetic loss of fresh ice in microwave range at a temperature of 0°C

The decay of microwave radiation in melting fresh ice is studied in the millimeter wavelength range (at frequencies of 90 and 34 GHz). It is demonstrated that ice at a temperature of 0°C may exhibit a decrease in the electromagnetic loss up to several tens of percents presumably due to the streamflow in the presence of internal mechanical stress or complete absence of loss at different stages of melting.     

加载横电磁传输室中的电场分布计算

用“准静脉法”研究了当工作频率远低于截止频率时,放置于横电磁传输室中的被测物体中的电场分布。文中使用的是有限差分法,给出了在三维空间中不同介质交界面上拉普拉斯方程的差分格式。计算结果表明当把ＥＴＵ放入ＴＥＭＣｅｌｌ的中心时,ＥＵＴ横截面上的电场分布是均匀的。     

基于FDTD的偶极子电场传感器幅频特性分析

介绍了时域有限差分(FDTD)法的理论与基本原理。利用该方法,得到了可对集成光波导偶极子电场传感器幅频特性进行理论分析的数学表达式。为优化器件性能,利用仿真,对在低频与高频电磁波入射时,不同电极长度/宽度下的器件幅频特性进行了比较。结果表明,低频电磁波入射时,采用较长或较窄的电极,均可提高器件的响应幅度;改变电极长度与宽度,对器件响应频率几乎没有影响。高频电磁波入射时,采用较长或较窄的电极,器件同样可获得较大的响应幅度;改变电极宽度,对器件响应频率的影响很小,但较长的电极会显著降低器件的响应频率。     

太赫兹波段电磁超介质的应用及研究进展

太赫兹波和电磁超介质是电磁学领域关注的热点.太赫兹波与电磁超介质相互作用可以实现对太赫兹波的操纵和调控,有望填补"太赫兹空白".介绍了太赫兹波段电磁超介质的研究进展,包括电磁超介质电磁性能可调谐的实施途径,电磁超介质在太赫兹功能器件方面的应用(调制器/开关、传感器/探测器、滤波器、偏振元件和吸波器),太赫兹波段表面等离...     

The resonant terahertz response of a slot diode with a two-dimensional electron channel

The terahertz response of a slot diode with a two-dimensional electron channel is calculated on the basis of the first principles of electromagnetism. It is shown that all characteristic electromagnetic lengths (scattering, absorption, and extinction lengths), as well as the impedance of the diode, exhibit resonances at plasmon excitation frequencies in the channel. The fundamental resonance behaves similarly to the current resonance in an RLC circuit. It has been concluded that, even at room temperature, a slot diode with a two-dimensional electron channel provides a resonant circuit at terahertz frequencies that couples effectively to external electromagnetic radiation with a loaded Q-factor exceeding unity. The diode resistance may be measured from contactless measurements of the characteristic electromagnetic lengths of the diode.     

The generation of optimal microwave topologies using time-domain field synthesis

We present a novel approach to the design of microwave structures using time-domain field synthesis. A standard transmission-line matrix (TLM) electromagnetic analysis of the starting geometry yields the structure response and the field distribution on the optimizable boundary parts. A number of characteristic frequencies equal to the number of designable parameters of the structure are determined first. For narrow-band structures, these frequencies may be natural resonance frequencies. For wide-band structures, we create appropriate resonance conditions. The target response of the structure allows us to identify the desirable values of these frequencies. For each parameter, a synthesis phase is then performed. In this phase, the optimizable boundary parts are replaced by matched TLM sources that inject sampled sinusoidal streams at the desired characteristic frequency. The TLM field model generates an electromagnetic field pattern. The synthesized geometry is obtained by examining the envelope of that field pattern. Our approach is illustrated by means of several examples.     

Shifted-frequency internal equivalence

The shifted frequency internal equivalence (SFIE) theorem involving inhomogeneous regions is introduced and proven. For a lossless inhomogeneous region using a vector Green's theorem and potential formulation, it is shown that the frequency-domain electromagnetic field at frequency ω inside the region can be obtained using a set of equivalent volume and surface currents radiating in free space and at the different frequency ω₀. The equivalent currents thus obtained are functions of the two frequencies, electric- and magnetic-volume-type sources of the original problem, material parameters, and the original field phasors at ω, and they only exist inside the region and on its boundary. A direct application of this equivalence is that it can be used to construct an internal equivalence at a shifted frequency for electromagnetic scattering problems if data are needed in a band of frequency. ω₀ can be kept constant while the incident field frequency changes and, as a result, full computation of fields at each different frequency for volume-type equivalent sources can be avoided     

MEMS Based Structurally Tunable Metamaterials at Terahertz Frequencies

We present the design, simulation, fabrication and characterization of structurally tunable metamaterials showing a marked tunability of the electric and magnetic responses at terahertz frequencies. Our results demonstrate that structurally tunable metamaterials offer significant potential to realize novel electromagnetic functionality ranging from dynamical filtering to reconfigurable cloaks or detectors. Furthermore, this approach is not limited to terahertz frequencies and may be readily used over much of the electromagnetic spectrum.     

One-directional gain and frequency selection of electromagnetic waves in a medium with a running grating of inverse population

The effects of one-directional amplification, frequency selection and transformation of time structure of electromagnetic waves (the generation of ultra-short pulses) are considered theoretically for a medium, where the creation of a running wave of atomic states inverse population is possible under excitation by coherent light beams with different frequencies and directions. These effects are due to the possibility of synchronism of a group velocity of an amplified electromagnetic wave with the phase velocity of a wave of inverse population. The general theory is applied for describing two specific cases which are observed in CdS crystals where the gain effects are caused by: 1) radiative transitions on lines generating the P-band of recombination radiation (the visible range) and 2) radiative transitions between different exciton subbands (the far IR range).     

光纤陀螺电磁干扰试验分析

为研究光纤陀螺的抗电磁干扰性,设计了电磁干扰试验,利用方差分析研究了电磁频率对光纤陀螺输出的影响.利用一元方差分析得出,单频率点电磁干扰对光纤陀螺无明显影响,而频率扫描电磁干扰对光纤陀螺的影响显著.利用二元方差分析进一步确定,频率扫描电磁干扰对光纤陀螺的影响与所加的频率段及光纤陀螺的运动状态有关.     

Simple method for investigating electromagnetic properties of high-Tc superconductors at two-millimeter wavelengths

A method for investigating the electromagnetic properties of high-T_c superconductors (HTS) in a 2-mm wavelength band has been proposed. The method is based on the use of a cylindrical tube open dielectric resonator (ODR) loaded with a HTS sample. The Josephson harmonic generation at microwave frequencies can be investigated by means of the method. A small cross section of the ODR makes it possible to investigate surface variations of HTS sample electromagnetic properties and their temperature dependencies.     

All-dielectric one-dimensional periodic structures for totalomnidirectional reflection and partial spontaneous emission control

A remarkable property of one-dimensional (I-D) alldielectric periodic structures has recently been reported, namely, a 1-D structure can totally reflect electromagnetic wave of any polarization at all angles within a prescribed frequency region, Unlike their metallic counterpart, such all-dielectric omnidirectional mirrors are nearly free of loss at optical frequencies. Here we discuss the physics, design criteria and applications of the thin-film all-dielectric omnidirectional mirror. The experimental demonstration of the mirror is presented at optical frequencies     

Twofold Mur's first-order ABC in the FDTD method

In this paper, it is shown that the reflection error of Mur's first-order absorbing boundary condition (ABC) can be canceled effectively by applying the ABC twice to an electromagnetic (EM) field on two diagonally neighboring nodes on the x-t, y-t and t-t planes. Following this idea, we have developed a twofold Mur's first-order ABC (TMFABC), which is efficient to absorb both propagative and evanescent EM waves and very convenient for implementation to multilayered structures. TMFABC improves Mur's first-order ABC more effectively at lower frequencies. This is very important because most energy of a high-speed pulse is concentrated at lower frequencies