基于半解析递归卷积的通用色散介质FDTD方法

基于数字信号处理中的半解析递归卷积（SARC）算法,提出了一种用于色散介质电磁特性分析的半解析递归卷积时域有限差分方法（SARC FDTD）. 该方法既保持了FDTD方法处理复杂目标的灵活性,又吸取了线性系统SARC算法的绝对稳定性和高精度、低内存、高效率等优点,只需给出色散介质模型的极点和对应系数,即可运用SARC FDTD递推公式和通用程序进行计算,具有较好的通用性. 通过Debye,Drude和Lorentz三种常用色散介质模型对算法进行了验证. 关键词： 时域有限差分 色散介质 半解析递归卷积     

Full-wave parallel dispersive finite-difference time-domain modeling of three-dimensional electromagnetic cloaking structures

A parallel dispersive finite-difference time-domain (FDTD) method for the modeling of three-dimensional (3-D) electromagnetic cloaking structures is presented in this paper. The permittivity and permeability of the cloak are mapped to the Drude dispersion model and taken into account in FDTD simulations using an auxiliary differential equation (ADE) method. It is shown that the correction of numerical material parameters and the slow switching-on of source are necessary to ensure stable and convergent single-frequency simulations. Numerical results from wideband simulations demonstrate that waves passing through a three-dimensional cloak experience considerable delay comparing with the free space propagations, as well as pulse broadening and blue-shift effects.     

Optics in spatially dispersive media: The energy theorem and the boundary conditions

The optics of spatially dispersive media is developed starting from a macroscopic material equation in differential form. The energy theorem is reformulated exhibiting the energy density, energy flux and the absorption density of polaritons. The 6 boundary conditions needed at an interface between to spatially dispersive media are derived.     

等离子体涂覆目标散射特性SARC FDTD方法分析

基于数字信号处理中的半解析递归卷积(SARC)算法,提出一种用于色散介质电磁特性分析的通用递归卷积时域有限差分方法(SARC FDTD),不仅具有绝对稳定性和高精度、低内存、高效率等优点,而且对于常见色散介质模型,具有统一的形式,计算时只需给出色散介质模型的极点和对应系数,使用方便,通用性好.通过算例验证了方法的有效性,并对有等离子体存在的目标电磁散射截面(RCS)进行了计算和分析.     

一种处理Cole-Cole色散媒质的FDTD改进方案

对柯尔-柯尔(Cole-Cole)色散媒质的时域有限差分(FDTD)方案尝试给出改进:(1)保留了Cole-Cole经验公式中的静态电导率项;(2)扩展到三维情形;(3)人体乳房组织的模型参数源于实验测量.数值算例结果初步证实改进方案的可行性和有效性.改进方案适用于模拟更一般柯尔-柯尔色散媒质中的电波传播.     

高斯波束在双负媒质中的传播特性分析

 提出了一种基于Drude色散媒质模型的2维TM模时域有限差分法，数值模拟了高斯波束从自由空间垂直入射和斜入射到双负媒质(介电常数和磁导率同时为负)平板后的折射现象，并给出了平板内外的电场强度分布。模拟结果显示：垂直入射时，双负媒质平板对高斯波束具有汇聚作用，通过改变媒质的折射率，可以控制高斯波束通过组合平板的传播时间而不发生衰减；斜入射时，折射波束与入射波束均位于法线的同一侧，高斯波束在双负媒质与空气交界面处发生了负折射。     

A generalized 2D FDTD model for photonic crystal fibers with frequency dependent media

A generalized model based on the two-dimensional finite-difference time-domain (2D FDTD) method for photonic crystal fibers (PCF) with frequency dependent media is presented. The Maxwell’s curl equations are formulated using flux density and the magnetic field. Auxiliary differential equations are used with complex-conjugate pole-residue pairs which incorporate the material dispersion of the dispersive media. The model is demonstrated to be a unified approach for arbitrary dispersive materials; therefore, it definitely reduces implementation cost when dealing with different frequency-dependent materials.     

等离子体的分段线性电流密度递推卷积FDTD算法

给出了一种新的色散介质的时域有限差分(FDTD)算法，称为分段线性电流密度递推卷积FDTD算法.利用电流密度和电场强度的卷积关系，给出了该算法的计算公式.通过计算碰撞冷均匀等离子体平板对电磁波的反射系数和透射系数，验证了该算法的高效性和高精度. 关键词： 色散介质 FDTD算法 电磁波     

色散媒质中的理想匹配层吸收边界及其误差分析

根据色散媒质的性质及电磁波在不同媒质交界面上的反射的机理，证明并分析了在理想匹配层吸收边界中引入色散可实现有效吸收入射到吸收边界上的电磁波，从而达到减少时域有限差分法计算区域和计算误差的目的。     

Analysis of the temperature influence on the plasma reflectance by a new FDTD method

We apply the shift-operator FDTD (SO-FDTD) method for calculating dispersive media plasmas. We write the dielectric constant of a dispersive medium as a rational fractional function and derive the relation between D and E in the time domain. For a uniform, approximately isothermic, isotropic, warm-collision-plasma slab, the reflection coefficient of electromagnetic waves can be calculated using the SO-FDTD method. We study the influence of temperature on the collisions and absorption of electromagnetic waves in the plasma and discuss the regularity of the relationships obtained.     

色散介质电磁特性时域有限差分分析的Newmark方法

根据Debye模型、Drude模型和Lorentz模型3种常见色散介质模型频域极化率的特点,利用频域到时域的转换关系jω→?/?t,将极化矢量P与电场强度E的频域关系转换成时域内关于P的二阶微分方程,其对3种色散介质模型皆适用,具有统一的形式.然后采用相比于中心差分具有更高精度的Newmark两步算法(Newmark-β-γ法)求解该方程,进而得到E→P的递推公式,再结合本构关系得到D→E的时域递推式.实现了色散介质电磁场量的时域有限差分迭代计算.数值计算结果表明该方法是适用于3种色散介质模型的通用算法,并且相比于移位算子时域有限差分方法等以中心差分为基础的离散方案具有更高的计算精度.     

复杂色散介质电磁特性分析的扩展Newmark-FDTD方法

基于有限元中的Newmark算法,提出一种新的色散介质时域有限差分（FDTD）方法,称为扩展Newmark-FDTD方法,它不仅可以用统一的方式处理Debye、Drude、Lorentz等常见色散介质问题,还可以统一处理修正Lorentz、二阶复有理函数等新的色散模型及其混合模型问题,且具有更高的计算精度和较好的稳定性.最后,通过算例对该算法的有效性进行验证.     

A novel CN–ICCG–FDTD algorithm research of plasma reflection and transmission characteristics of electromagnetic wave

The advantage of the ICCG method for solving large sparse matrix is taken in the CN–FDTD equation solving. The CN–ICCG–FDTD can accelerate iteration for numerical calculation, and reduce memory overhead. Maxwell's equation of the electromagnetic wave in dispersive medium plasma is deduced from the CN format after being differentiated in the time domain, the FDTD method become unconditionally stable. In this process, a large sparse matrix is generated. As for solving such matrix, ICCG method has sufficient advantages. In ICCG method, convergence is so fast and stable that it is quite easy for computer programming. In addition, data required by ICCG method are memorized in a computer in the format of the one-dimensional compression, which helps the computer memory save a large amount of capacity, especially when the issues are rather complex to cope with, this algorithm will display such strength. With these advantages, ICCG method is able to calculate the reflection coefficient and the transmission coefficient of electromagnetic waves in plasma as well as the phase angle of them. The calculation indicates that the time step required by CN–ICCG–FDTD method has eliminated the constraints of the CFL, thus shortening the required time, making the calculated result stable and accurate, and improving the efficiency of programming.     

An FDTD method for the simulation of dispersive metallic structures

In this paper, we present a formulation of the finite-difference time-domain method for the simulation of metallic structures. The frequency dependent dielectric function of metals is approximated by a combined Drude–Lorentzian multi-pole expansion and fitting errors of only a few percent are obtained. An auxiliary differential equation technique is used to extend the standard FDTD algorithm with the dispersive material equations. The algorithm is validated by calculating reflection and transmission coefficients for thin metal layers, elliptical nano-particles and by simulating a surface plasmon resonance device. Excellent agreement between the FDTD simulations and exact theoretical results are obtained.     

Frequency response of 1D dispersive sea surface by the ADE-FDTD algorithm

The frequency response of a one-dimensional (1D) sea surface was investigated using the finite-difference time-domain (FDTD) algorithm with pulsed wave excitation. Where the sea water is regarded as an isotropic and dispersive medium, it satisfies the single-pole Debye model. The auxiliary differential equation (ADE) technique is incorporated into the FDTD scheme to deal with the dispersive sea surface. To ensure the feasibility of our present method, the frequency response of dispersive sea surface by the ADE-FDTD method is compared with the result by the conventional method of moments (MOM), which requires an individual calculation for every frequency point of interest. Finally, the scattering characteristic of dispersive sea water is investigated for different wind speed, temperature, and salinity. The representative far zone scattered field versus time is also analyzed.     

A FDTD formulation for high order dispersive media of muscle-equivalent

In this paper, shift operator finite-difference time-domain (SO-FDTD) method is applied for the calculation of the dispersive medium. The high efficiency and accuracy of this method is verified by calculating the reflection of the plane electromagnetic wave impinging on a muscle slab. For human tissues where multiterm Debye relaxation equations must generally be used. We describe a new differential equation approach, which can be used for general dispersive media. In this method D(t) is expressed in terms of E(t) by means of a differential equation involving D, E, and their time derivatives. The method is illustrated by means of example of media for which relative permittivity is given by a multiterm Debye equation, and for an approximate two-thirds muscle-equivalent model of the human body.     

一维等离子体光子晶体的带隙研究

采用时域有限差分方法(FDTD),结合等离子体计算中的分段线性电流密度卷积技术(PLJERC)对一维等离子体光子晶体(1D-PPC)进行了数值模拟,给出了微分高斯脉冲在一维等离子体光子晶体中的传播过程。计算得到的带隙结构与K-P模型方法的结果一致。计算并分析了等离子体频率、介质介电常数、等离子体-介质层的厚度比以及周期厚度对一维等离子体光子晶体带隙结构的影响。     

磁化铁氧体覆盖二维导体目标FDTD分析的移位算子方法

采用移位算子方法把时域有限差分法推广应用于二维磁各向异性色散介质—磁化铁氧体中.证明了电磁波横向入射二维轴向磁化铁氧体目标情形下,电磁波可按目标的轴向分解为横电波(TE波)和横磁波(TM波),且TE波的散射特性与铁氧体介质无关,而TM波的散射特性与介质电磁参量密切相关,同时对其物理原因进行了分析.通过采用移位算子方法处理磁化铁氧体频域本构关系,得到该情形下目标电磁散射的移位算子时域有限差的迭代计算公式,同时解决了电磁波在各向异性和频率色散介质中传播的问题.计算了轴向磁化铁氧体涂敷VonKarman型导体柱的TM波双站雷达散射截面,分析了铁氧体参量对目标双站雷达散射截面的影响.结果表明:恰当地选择铁氧体参量能有效地减少目标的雷达散射截面,本文时谐因子取exp〔jωt〕.     

运用有限差分时域法计算具有径向色散特性的圆柱形隐形斗篷

提出了一种具有径向色散特性有限差分时域法（FDTD法）的电磁隐形斗篷建模.隐形斗篷的介电常数和磁导率是采用了drude色散模型以及相应的色散FDTD算法.数值模拟表明,在理想的条件下,隐形斗篷中的物体对外电磁场是隐形的.对于入射平面波和点声源,波前平滑地进入隐形斗篷,并绕过中心的物体区域,离开隐形斗篷后又恢复为原来的传播状态.远场散射图表明,与一个理想导体圆柱相比隐形斗篷可以减少沿各个方向的散射.     

色散周期结构的辅助场时域有限差分法分析

利用辅助场时域有限差分(FDTD)方法分析色散周期结构的斜入射问题. 主要基于Floquet定理, 在FDTD迭代式中引入辅助场量, 结合变换的周期及吸收边界条件,解决了周期结构斜入射问题的电磁特性仿真. 进一步将辅助场FDTD方法引入至色散周期结构的模拟, 结合Z变换方法,给出了基于Drude色散模型的具体迭代公式. 数值计算结果表明所构建方法的有效性及普适应.