Drawing glass fibers with complex cross section

Techniques are presented for fabrication of glass fibers with complex cross-sectional shapes by drawing from a composite preform. To prevent distortion of the fiber shape by surface tension during drawing, a soluble glass cladding is added to the preform complete its cross section to a circular shape. After the drawing process, the cladding is dissolved chemically. Fibers with zigzag and meander-like cross sections and minimum dimensions of 2 μm are demonstrated     

单轴双各向异性媒质柱体的电磁散射

采用广义多极子技术（Ｇｅｎｅｒａｌｉｚｅｄ Ｍｕｌｔｉｐｏｌｅ Ｔｅｃｈｎｉｑｕｅ,ＧＭＴ）分析了单轴双各向异性媒质任意截面柱体的电磁散射,计算结果与解析解和矩量法（Ｍｅｔｈｏｄ ｏｆ Ｍｏｍｅｎｔｓ,ＭｏＭ）所得结果一致,讨论了该方法在电磁散射应用中的优缺点。     

Modeling lossy anisotropic dielectric waveguides with the method oflines

This paper presents a new formulation useful for modeling waveguides constructed from lossy inhomogeneous anisotropic media. Our approach is based on a pair of Sturm-Liouville type wave equations that have been derived to handle inhomogeneous, diagonalized complex permittivity and permeability tensors. The method of lines is then applied to these wave equations, and related field equations, creating an indirect eigenvalue problem that correctly models this class of structure. Some refinements to the method of lines are also proposed, particularly, regarding the construction of the modal matrices found in the eigenvalue problem. Using our approach, modal dispersion curves have been computed for millimeter-wave and optical structures. Comparisons made with results available from the literature validate our approach     

Simple analysis of anisotropic microstrip lines by a transform method

For the TEM-mode investigation of microstrip lines on anisotropic substrates, a simple, but rigorous, transformation is introduced, which converts the anisotropic electrostatic field into an isotropic one with similar shape; the latter has been extensively analysed in the past. The transformation also applies to related anisotropic problems. Results for single and coupled lines are presented. Dispersion is briefly commented on.     

Quick quasi-TEM analysis of multiconductor transmission lines withrectangular cross section

This paper presents an efficient and accurate procedure for computing the quasi-static matrix parameters ([C], [L], [G], and [R]) of rectangular-shaped conductors embedded in a multilayered dielectric medium over an infinite ground plane. An additional top ground plane can also be considered., The problem is formulated in terms of the space-domain integral equation for the free-charge distribution on the slab conductor surfaces. The spatial Green's function is computed from its spectral counterpart using system identification techniques [Prony's method or matrix pencil method (MPM)]. The integral equation is solved by means of a Galerkin scheme employing entire domain basis functions. This results in a small matrix size. In addition, the quasi-analytical evaluation of the entries of the Galerkin matrix leads to a very efficient and accurate computer code. A detailed study on the convergence and accuracy of the method has been included     

Efficient and accurate modeling of planar anisotropic microwavestructures by the method of lines

A new algorithm for the analysis of planar microwave structures with anisotropic substrates is proposed and substantiated. This algorithm is based on generalized transmission-line (GTL) equations, which are developed here for numerical algorithms. For the purpose of analysis, two different modal matrices for the discretized transverse electric and magnetic fields are calculated. Furthermore, impedance/admittance transformation formulas are developed with the help of the GTL equations for longitudinal sections and general junctions. Crossed discretization lines are used in the latter case. The materials are assumed to be biaxial or specific anisotropic. Special algorithms are developed for junctions consisting of more than two waveguides in the cross section and for bends. The proposed algorithm is verified by numerical results     

Evaluation of the radar cross section of circular microstrippatches on anisotropic and chiral substrates

Galerkin's method in the Hankel transform domain (HTD) is applied to the determination of the radar cross section (RCS) of a circular microstrip patch printed on a substrate which may be an uniaxial anisotropic dielectric, a magnetized ferrite, or a chiral material. The results obtained for circular patches on magnetized ferrites show that the RCS of these patches can be substantially reduced in a tunable frequency band when a bias magnetic field is applied. It is also shown that the results obtained for the RCS of circular patches printed on chiral materials can be substantially different from those obtained when substrate chirality is ignored     

Analytic method of arbitrary cross section open groove guide

Groove guide is one of the waveguides that have been used at millimeter and submillimeter waveband. This paper analyzes arbitrary groove guides by means of the eigen-weighted boundary integral equation method that uses the eigenfunctions of a fictitious regular boundary as weighting functions. In comparison with the theoretical and experimental results published, the numerical results for rectangular, circular and V-groove guides using this method are exact enough with fast convergence and less calculation.     

Analytical solution of stresses and material birefringence inoptical fibers with noncircular cladding

An analytical method for the calculation of thermal stress in polarization-maintaining optical fibers is presented. The method is based on the thermoelastic potential and is appropriate for structures with a noncircular stress-cladding boundary. The analytical solution is compared with the results of the finite element method (FEM) for the case of an elliptical boundary     

基于图形电磁学的雷达散射截面计算方法改进

图形电磁学(GRECO)可以高效计算电大目标雷达散射截面(RCS)。但传统GRECO算法无法直接计算双站RCS和仿真多次反射,存在计算精度依赖屏幕分辨率的缺点。文中提出了基于渲染后的像素信息还原目标几何信息的方法,使其能够计算双站RCS,并结合弹跳射线法(SBR)计入多次反射的影响。同时,研究基于帧缓存对象(FBO)的离屏GRECO方法,克服了其计算精度依赖屏幕分辨率的缺点。     

Absorption and emission cross section of Er3+ dopedsilica fibers

A detailed set of measurements is presented on determining the emission and absorption cross sections of Er³⁺ doped fibers for the ⁴I_13/2→⁴I _15/2 transition. Two techniques are employed: the Fuchtbauer-Ladenberg analysis, based on spectroscopic data, and a more direct technique involving optical saturation of the transition. The cross sections, and in particular their ratio, are significantly different for the two techniques. Possible reasons for this are discussed, and it is concluded that the Fuchtbauer-Ladenberg approach is inappropriate in this situation     

一种角反射体雷达散射截面积的高频预估算法

几何光学/区域投影(Geometrical Optics/Area Projection, GO/AP)法是一种综合利用GO和AP进行电大尺寸目标单站雷达散射截面积(Radar Cross Section, RCS)预估的高频混合算法.文章推导建立了利用GO/AP法进行RCS预估的通用流程, 计算出不同入射方向下三角形三面角反射RCS的完整表达式; 将其与RCS最大值的经验公式以及FEKO软件的仿真结果进行对比, 验证了GO/AP法的可行性; 在边界入射方向对GO/AP算法进行改进, 进一步拓宽了GO/AP法对观察角的适应范围.     

单轴各向异性球对任意方向入射平面波的散射

基于球矢量波函数的正交完备性,给出了具有任意传播方向两种极化模式的平面波用球矢量波函数展开的形式,导出了其展开系数的具体表达式．研究了单轴各向异性介质球对任意方向入射平面波的散射,利用球矢量波函数及傅里叶变换方法得到了各向异性介质球的内场展开式,结合切向连续边界条件给出了散射系数．数值分析了介电常数张量元、有耗、无耗、尺寸参数、入射角和方位角等对单轴各向异性介质球的雷达散射截面的影响．     

Boundary-marching method for discontinuity analysis in waveguidesof arbitrary cross section

A recursive algorithm previously used in diffusion problems of geophysics and in electrostatics is extended to wave phenomena. It is used to construct a matrix representation for an infinitely long waveguide of arbitrary cross-sectional shape. This representation is used in finite-element analysis of waveguide discontinuities. In numerical tests, scattering matrices for the long guides converge to nearly full word-length in six to seven recursion steps, and discontinuity characteristics are within 1-2% of known results where they exist     

A hybrid method for the calculation of the resistance andinductance of transmission lines with arbitrary cross sections

The frequency-dependent resistance and inductance of uniform transmission lines are calculated with a hybrid technique that combines a cross-section coupled circuit method with a surface integral equation approach. The coupled circuit approach is most applicable for low-frequency calculations, while the integral equation approach is best for high frequencies. The low-frequency method consists in subdividing the cross section of each conductor into triangular filaments, each with an assumed uniform current distribution. The high-frequency method expresses the resistance and inductance of each conductor in terms of the current normal to the surface. An interpolation between the results of these two methods gives very good results over the entire frequency range, even when few basis functions are used. Results for a variety of configurations are shown and are compared with experimental data and other numerical techniques     

一种采用吸波透波超表面的天线RCS宽带减缩新方法

设计了一款具有吸波/透波双重特性的超表面,并将其用于微带天线的覆层,实现天线雷达散射截面(radar cross section, RCS)的宽带减缩. 将传统的结构性吸波材料金属单元用氮化钽材料置换,提升了吸波带宽. 同时,将吸波材料与频率选择表面相结合,实现了覆层对于不同来波方向的电磁波分别呈现吸波/透波两种截然不同的电磁特性. 将覆层置于天线上方,当天线工作时,天线辐射的电磁波可以完美穿过覆层,因此对于天线的辐射特性不会造成影响. 当雷达波照射至天线时,覆层所呈现的宽带吸波特性可最大程度降低天线的RCS. 仿真结果表明:使用本文所设计的吸波/透波超表面作为天线覆层时,天线的辐射特性几乎未发生变化;而天线的单站RCS最大减缩量可达20 dB以上,减缩带宽可达5～19 GHz;同时,天线的单、双站RCS在较宽的角度范围内也得到明显的缩减.     

Computerized ray optics method of calculating average value radar cross section

In attempting to estimate the radar cross section of airborne vehicles, it is often only necessary to consider average values of the radar returns. A method of providing a quick estimate of the average bistatic radar cross section of the vehicle components would be useful. Ray optics provides a method of predicting the radar cross section of electrically large, perfectly conducting, simply curved, convex bodies such as spheres, ogives, ellipsoids, etc. This paper extends the method of ray optics to the case of an arbitrary body, which may be concave and/or convex, on which doable reflection and depolarization can occur. The incident radiation on the scattering body is represented by a large number(10^{5}-10^{6})of rays. The rays reflected in a given direction with a given polarization are collected at infinity and combined by phasor addition. For the bodies investigated, this method yields results withinpm2dB of measured results except in small angular regions where trapped waves contribute significantly to the radar return.