各向异性介质在三维ADI-FDTD中的应用

该文研究一种减小三维交替方向隐式时域有限差分法(ADI-FDTD)数值色散的新方法。通过在三维空间中合理添加各向异性介质,达到调整相速的目的,从而减小数值色散,使计算结果更加精确。首先对添加各向异性介质后的三维ADI-FDTD迭代公式进行变形,并得到新的数值色散关系,从而求解得到各向异性介质的相对介电常数。以空心波导和具有介质不连续性的波导作为数值算例,分析不同的各向异性介质和添加方法对计算精度的影响,并与传统ADI-FDTD得到的结果和计算资源占用情况进行比较。结果表明通过正确选择各向异性介质和添加方法,可以有效地减小三维ADI-FDTD数值色散。     

不同抽运光分布的Nd:GGG热容激光器介质热应力分析

从固体瞬态热传导微分方程出发并结合弹性力学的基本方程,利用有限元方法对Nd:GGG热容激光器介质的瞬态温度和热应力进行了数值模拟.数值模拟并分析了介质端面抽运光为均匀分布和高斯分布两种情况下,介质的温度、应力的瞬态分布.模拟中考虑了由介质的吸收特性导致的介质热沉积功率不均匀分布和介质热容随温度的变化关系.结果表明,抽运光功率一定时,抽运光均匀分布时介质的最高温度较低,温度梯度较小,介质所受热应力较小.     

强激光非线性热像与克尔介质厚度的关系

通过理论分析与数值模拟方法,研究了高功率激光系统中非线性热像位置及光强随介质厚度的变化规律。基于角谱传输和Bespalov-Talanov小尺度自聚焦理论,在不作薄介质近似情况下得到了热像光强表达式,并用数值模拟结果进行了验证。结果表明,在一定的入射功率下,热像光强随介质厚度的增加而增大;而在一定的B积分下,热像光强随介质厚度的增加先单调增加,达到一极大值后,单调减小。此外,当模糊斑相对于克尔介质的距离的菲涅耳数远大于1时,可采用薄介质近似。数值模拟结果与解析结果吻合得很好。     

多层介质槽线的传输特性研究

本文基于严格的电磁场理论,全波分析了多层介质槽线,推导了不同介质区中电磁场的递推关系,建立了稳定的,且仅以槽中电场为未知参量的槽线传输特性的计算公式。作为示例,数值计算了双层介质槽线和夹层介质槽线,数值结果与文献中的数据相符。     

计算多介质层矩形微带天线谐振频率的解析方法

提出一种分析多介质层矩形微带天线的解析方法。首先导出了计算多介质层微带线的等效相对介电常数的显式计算公式，进而得到了多介质层矩形微带天线谐振频率的解析计算公式和一些数值结果。与精确的数值方法结果和实验值作了比较，它们吻合得很好。本方法运算简单，特别适合于ＣＡＤ应用。     

大统计斜率随机表面光散射的Monte Carlo数值模拟

本文在Ｋｉｒｃｈｈｏｆｆ近似的基础上，通过Ｍｏｎｔｅ Ｃａｒｌｏ数值模拟，分析了大统计斜率随机表面的单次和二次散射。数值结果证明了导体和介质表面均存在起因于多次散射的后向增强散射，入射光的偏振状态对介质表面散射特征有明显的影响。数值结果与实验报导有很好吻合。     

半导体侧面泵浦固体激光器均匀性的计算和分析

建立了半导体侧面泵浦固体激光介质内泵浦光能吸收分布情况的数值模型。模拟计算了不同泵浦参数下棒状介质和板条介质内泵浦光能的吸收分布,计算结果和有关实验结果符合得很好。得出了半导体侧面泵浦机构中介质尺寸、介质吸收系数和半导体激光器发光面到介质泵浦面距离这三个参数对泵浦均匀性的影响,比较了棒状介质和板条介质在半导体侧面泵浦应用中的优劣。     

各向异性丛林介质的色散关系

对任意张量的介电常数和磁导率,本文给Jj!了其色散关系;对丛林介质, 将上述关系进一步简化,导川丁各向异性丛林介质的包散关系j利用介电常数和磁导率张量进行数值计算,得到了J(色散方程小系数的数值结果。     

非均匀介质中的场与波：理论及其在电测井中的应用

本文综述了非均匀介质中场与波理论近年来的研究进展及其应用成果，着重介绍了非均匀介质中的电磁场正演分析和反演计算中的各种高效数值方法，以及它们在电法测井数值模拟和成象研究中的成功应用。     

胆甾型液晶彩色滤光片分析

计算了掺有周期性介质层的胆甾型液晶(CLC)膜的反射光色品值,分析了该膜用于滤光片的可行性。首先利用Jones矩阵法对其反射光谱进行了数值计算,然后分析和比较了掺入周期性介质前后液晶膜的CIE-1931色品图。从数值计算可知,在适当的液晶和介质厚度比例下,改变斜入射角度对掺有周期性介质层的反射式胆甾型液晶滤光片的反射光色品值改变不大,可以起到窄带滤光片的作用。     

A new algorithm for electromagnetic scattering of multilayered sphere

More stable and accurate recursive formulas and a computing procedure for scat-tering coefficient calculation of a multilayered sphere are proposed, This procedure involves threelogarithmic derivatives of Ricatti-Bessel function ψ_n~＇(z)/ ψ_n(z), X_n~＇(z)/X_n(z),ξ_n~＇(z)/ ξ_n(z), as wellas the ratioψ_n(z)/X_n(z). The asymptotic behavior, stability, and accuracy of the procedureand scattering coefficients a_n and b_n are discussed for various complex refractive indices. Thisprocedure can be applied to large and small inhomogeneous spherical particles.     

Scattering Coefficients for Wall Impedance Changes in Waveguides

The Wiener-Hopf tectilque is used to obtain an exact solution to a two-dimensional scattering problem. In the problem solved, an incident TE/sub 10/ mode, traveling from z= -/spl infin/ in the positive z direction, is confined by infinite bounding planes; these planes have infinite conductivity for z<0 and an impedance Z/sub 1/, for z>0. The scattering from the junction at z=0 gives rise to reflection and transmission coefficients that are exactly determined. An approximate solution for the reflection coefficients is also given when the TE/sub 10/ mode is incident from the opposite direction. Finally, a table is presented which lists some transmission and reflection coefficients for rectangular and circular waveguides with discontinuities in the wall impedances.     

多层球对高斯波束的散射

本文根据广义米氏理论，将入射高斯波束用矢量球谐函数展开，研究多层介质球的电磁（光）散射，提出波束因子ｇｎ的改进算法以及散射系数ａｎ和ｂｎ的迭代公式和算法，并进行了数值计算与讨论。     

The Susceptance of an Annular Metallic Strip in a Circular Waveguide with Incident TE/sub 01/ Mode

The principal aims of this paper are twofold: 1) to solve the problem of the scattering of a thin, perfectly conducting aonular strip suspended in a multimodal circular waveguide in which any number of TE/sub 0n/ modes can propagate, and with the aid of this result, 2) to give the susceptance of the thin annular strip in monomodal circular guide with an incident TE/sub 01/ mode. These are treated with a variational approach. Applying the appropriate Green's functions to the continuity equations for the transverse electric field yields a variational expansion for the scattering matrix elements. This is treated with a Rayleigh-Ritz procedure and matrix methods. Curves of normalized susceptance as a function of the free-space wavelength and the size of the annular metallic strip are shown. These results are in good agreement with experimental data. Tables of the scattering coefficients for a typical wavelength versus strip size are also included.     

Electromagnetic dyadic Green's function in cylindricallymultilayered media

A spectral-domain dyadic Green's function for electromagnetic fields in cylindrically multilayered media with circular cross section is derived in terms of matrices of the cylindrical vector wave functions. Some useful concepts, such as the effective plane wave reflection and transmission coefficients, are extended in the present spectral domain eigenfunction expansion. The coupling coefficient matrices of the scattering dyadic Green's functions are given by applying the principle of scattering superposition. The general solution has been applied to the case of axial symmetry (n=0, n is eigenvalue parameter in φ direction) where the scattering coefficients are decoupled between TM and TE waves. Two specific geometries, i.e., two- and three-layered media that are frequently employed to model the practical problems are considered in detail, and the coupling coefficient matrices of their dyadic Green's functions are given, respectively     

On the filtering problem for stationary random /spl Zopf//sup 2/-fields

It is shown that whenever a stationary random field (Z/sub n,m/)/sub n,m/spl isin/z/ is given by a Borel function f:/spl Ropf//sup z/ /spl times/ /spl Ropf//sup z/ /spl rarr/ /spl Ropf/ of two stationary processes (X/sub n/)/sub n/spl isin/z/ and (Y/sub m/)/sub m/spl isin/z/ i.e., then (Z/sub n, m/) = (f((X/sub n+k/)/sub k/spl epsi/z/, (Y/sub m + /spl lscr// )/sub /spl lscr/ /spl epsi/z/)) under a mild first coordinate univalence assumption on f, the process (X/sub n/)/sub n/spl isin/z/ is measurable with respect to (Z/sub n,m/)/sub n,m/spl epsi/z/ whenever the process (Y/sub m/)/sub m/spl isin/z/ is ergodic. The notion of universal filtering property of an ergodic stationary process is introduced, and then using ergodic theory methods it is shown that an ergodic stationary process has this property if and only if the centralizer of the dynamical system canonically associated with the process does not contain a nontrivial compact subgroup.     

Stationary expression for scattering coefficients at uniform piezoelectric waveguide junction

By using a modified expression of the orthogonality relation between normal modes, the stationary expression for the scattering coefficients at the uniform piezoelectric waveguide junction is obtained by a procedure similar to that used in electromagnetic waveguides. By the Rayleigh-Ritz method, the scattering coefficients are expressed by simple expression.     

PTD和PTDEEC算式的奇异点处理

将计算劈型目标电磁散射的ＰＴＤ绕射系统通过简单的三角变换写成另一种表达式，提高它们在奇异点邻域的数值稳定性，数值结果表明本文给出的公式在奇异点附近比原始的表达式要好。     

Improved numerical diffraction coefficients with application tofrequency-selective surfaces

A method for numerically determining diffraction coefficients for arbitrary scattering centers is described. In this method finite bodies possessing scattering centers of the type of interest are first analyzed via the moment method. The various contributions to the total scattered fields are then isolated by solving low-order simultaneous equations obtained by writing expressions for the fields in terms of unknown diffraction coefficients. The method yields numerical diffraction coefficients in angular sectors where previous methods fail (e.g., near grazing angles), and can be applied in the context of measured as well as simulated scattering data. Finite frequency-selective surfaces are shown to be amenable to analysis with ray-optics techniques, and several two-dimensional examples are given with comparisons to far- and near-field moment method results     

New technique for measuring the scattering coefficients of two-portdevices

A new technique (based on a extension of the six-port reflectometer procedure) is used to measure the scattering coefficients of two-port devices. Only six power sensors are required, as opposed to a total of eight for the dual-reflectometer scheme. Tests confirm that the nine-port instrument based on this technique is able to yield reasonably good measurement accuracies