采用保角变换求解一类TEM模传输线的衰减常数

本文提出采用保角变换法求解一类TEM模传输线的衰减常数。通过适当的保角变换能够映射成(包括数值保角变换)正规圆同轴线或平板电容的情况均可采用这种方法。文中给出了解析结果和数值实例。     

基于光学保角变换的电磁器件设计

保角变换是基于解析函数的一种非常重要的解析方法,利用保角变换可以将虚拟空间中复杂的边界曲线转化为物理空间中简单的边界曲线,从而求解二维平面场问题。文章主要综述并介绍保角变换在几何光学中的应用,通过控制光线传播来设计完美隐身衣、中继透镜、波导弯角和透镜天线等新型电磁器件。最后利用射线追踪仿真和全波仿真对设计加以证明。     

平面镜像法与有源保角变换

本文把镜像法与复保角变换有机地结合起来。指出对于实际中的一大类问题,只须采用平面镜像做基本模型,而对复杂形状作有源保角变换,就可以归结为平面镜像。特别有兴趣的是变换后的求解区域可以允许存在原问题∞处的镜像电荷,从而突破了一般镜像法的一个准则。     

DDM-CM理论及其在VLSI中的应用

阐述了保角变换理论的最新研究成果DDM-CM理论及其在VLSI中的应用。其最大的优点就是给出的结果比较简单、精确,并且在整个的计算过程中不需要求解保角变换函数,只要求得导体几何的保角模即可。     

矩量法结合保角变换求解复杂二维边值问题

本文论述矩量法结合保角变换求解复杂二维边值问题。它通过保角变换使一种结构变成另一种新的结构,通过矩量法和“Collin原则”的结合,估计了耦合线的参数的数值上下界。文中还给出了某些紧耦合情况的应用实例。     

斜平板波导的分析

应用保角变换的方法,对斜平板波导作了精确分析,导出了其分布电容及特性阻抗的求解公式,并给出 了几种不同情况的数值结果。     

全屏蔽共面波导的准静态分析

本文采用精确和近似的保角变换技术对全屏蔽共面波导结构的传输特性进行准静态分析,提供了这种结构特性阻抗的简明表达式。计算结果表明分析的正确性。     

带有小椭圆度的圆波导移相器

引言圆波导中的H_(11)模通过加载圆波导移相器后,能形成圆极化波。理论上要计算这类问题是非常困难的,而计算加载方波导的相移变化是有法可循的。于是,我们很自然的想到能否将加载圆波导保角变换为加载方波导,使问题得到简化。本文通过保角变换介绍了加载圆波导的一种近似的相移计算方法。理论计算和实测结果比较符合,误差小于1.3°。保角变换在复杂截面输传线的特性阻抗计算中的作用是     

计算复杂形状波导截止频率的高效方法

提出一种使用保角变换结合矩量法,计算复杂形状波导截止频率的新方法,该方法采用解析法或数值法,把复杂截面的波导变换为圆形区域,再采用矩量法求解波导的截止频率。实验结果验证了该方法的有效性。     

圆柱型微带线的准静态特性

本文以平面微带线为中介使用保角变换法研究了非平面圆柱型微带线的准静态特性。文中给出了特性分析公式，并确定了用二分法进行尺寸综合要求的操作区间和目标函数。最后，进行了数值结果比较，效果良好。     

基于光栅侧面耦合的宽光带集光技术

利用光栅侧面耦合技术多为单波长或窄带光耦合,用于光纤激光器泵浦、光波导集成等领域,而用于可见光宽带耦合的研究很少。通过在波导上集成亚波长衍射光栅结构,可以引导太阳光在波导的侧面进行出光汇集,作为一种新型的太阳能集光器结构。利用时域有限差分算法软件(FDTD)对光栅结构进行仿真,以获得最大衍射效率的光栅结构参数,并对不同入射角度下的衍射耦合效率进行了分析。结果显示,在宽波段的光谱范围内,以上光栅结构均达到较好的衍射效率,其中闪耀光栅衍射效率最大,其衍射效率可达48.8%。这种利用亚波长衍射光栅结构的小型集光器有望应用在有关太阳能能量的收集应用中,例如照明、太阳能电池等。     

A partial variational approach for arbitrary discontinuities inplanar dielectric waveguides

A novel approach for analyzing arbitrary discontinuities in planar dielectric waveguides is proposed that uses the finite-element method along with the frontal solution technique. On the basis of the partial variational principle (PVP), the fields interior and exterior to the discontinuity finite-element region can be treated independently and eventually can be coupled. The interior fields are expanded by the finite-element nodal values and the corresponding local bases, while the exterior ones are handled by an approach combining modal expansion and Green's function. In numerical computation, the continuous spectra of the waveguide modes are discretized by the Laguerre expansion method. To check the correctness of the present analysis, two numerical results are compared to those of other methods. The scattering characteristics of several linearly tapered discontinuities, such as transformers and feed structures, are analyzed and compared to those having step junctions     

Multilevel model order reduction

We present a multilevel Model Order Reduction scheme for enhancing numerical analysis of electromagnetic fields by means of grid based techniques. The scheme allows one to create nested macromodels and combine macromodels with the Fast Frequency Sweep. The implementation of the method is illustrated on the Finite Difference Frequency Domain technique and efficient nodal order reduction algorithm (ENOR) but the concept can easily be applied also for other mesh based methods and other order reduction schemes.     

Solution of the general Helmholtz equation in homogeneously filledwaveguides using a static Green's function

The new boundary-integral method used in this paper illustrates a novel approach to solve the general Helmholtz equation in homogeneously filled waveguides. Based on the method-of-moments Laplacian solution, the main feature of this formulation is that the Helmholtz equation is “reduced” to the Poisson's equation, which is then solved by using a static Green's function. In other words, the Green's function used in this method is frequency independent, unlike the most conventionally used Hankel functions. Hence, the computational time, while analyzing the waveguide over a range of different frequencies, is reduced considerably compared to other well-known numerical methods, since the frequency term just appears as a scaling factor in the evaluation of matrix elements. The numerical results obtained using the present method compare well with actual results (in the case of rectangular waveguides) and published results (in the ease of L-shaped and single-ridge waveguides)     

Reduced order models of refined Yee's cells

This letter introduces a new approach to increasing the accuracy of Finite Difference (FD) methods by means of local mesh refinement. The area slightly larger than single Yee's cell is covered by dense mesh and its macromodel is created by the Model Order Reduction (MOR) of state equations in the frequency domain. Such macromodels are subsequently used in the Finite Difference Time Domain (FDTD) or the Finite Difference Frequency Domain (FDFD) analysis of the entire structure. Unlike a popular subgridding technique, the model order reduction approach does not affect the stability or convergence properties of underlying numerical schemes.     

条形和脊型SOI 波导微环结构传感性能研究

使用时域有限差分(FDTD)方法研究了基于SOI微环谐振腔结构的条形和脊型波导,探究了微环谐振腔应用于生物传感的理论。分析了结构的几何尺寸对生物传感器灵敏度的影响。通过分析条形和脊型波导的模场分布图,解释了条形波导的灵敏度明显高于脊型波导的原因,且随着波导宽度的增加其灵敏度系数的变化遵循相同的趋势。并且,当条形波导取得最高的灵敏度系数时,其横截面是方形的,然而脊型波导的最大灵敏度值对应的却是不完全对称的几何结构。当条形波导的横截面全对称时,灵敏度达到最大值172.3 nm/RIU。     

Transient Analysis of Creeping Wave Modes Using 3-D FDTD Simulation and SVD Method

Creeping wave modes on smooth structures are of importance in the control of scattering properties, such as radar cross section of such structures. We have shown a novel procedure to examine the excitation of creeping wave modes by plane wave illumination of a perfectly electrically conducting (PEC) cylinder. Detailed information about transients of creeping wave modes and their spatial structure, have been obtained for the first time using Singular Value decomposition (SVD) analysis of 3D Finite Difference Time Domain (FDTD) data. The transient analysis shows how the amplitudes of different modes vary in time, and how the dominant modes eventually stabilize to the time-harmonic solution given by analytical methods. Although the method is computationally expensive, this technique will be particularly useful for purely transient signals, complex geometries and situations involving spatially-varying material properties such as a plasma shielded object.     

非线性薄膜中的导模

对于芯区为克尔型非线性介质,衬底和包层为线性介质的LNL型非线性光波导,给出了各层介质中的场分布和功率分布的数学表达式,纠正了Boardman和Egan在1986年发表的文章中的几处差错,给出了正确的色散方程,并对该文中的典型实例进行了计算,给出了数据和曲线,所得结果的正确性已采用了数值分析法进行过核验。     

A scalar variational conformal mapping technique for weakly guiding dielectric waveguides

A novel approach of combining the finite-element method with the conformal mapping technique is proposed for solving the scalar variational formulas for weakly guiding dielectric waveguides. This approach avoids spurious modes and gives satisfactory results even for modes near cutoff, requiring less computer memory and time. Various specific dielectric structures, such as the rectangular guide, channel guide, and rib guide, are considered to estimate the error associated with the scalar formulation relative to the vectorial formulation. The efficiency of this approach is demonstrated with an analysis of a directional coupler whose coupling properties are described by means of numerical results such as propagation constants, field distributions, etc.     

渐近波形估计技术加速的频域有限差分法

本文提出了一种基于三维频域有限差分法(3D-FDFD)和渐近波形估计技术(AWE)计算三维微波结构S参数的快速算法。在分析中,将输入和输出端口的电场分别展开成某抽样频率点处的泰勒级数,通过Pad逼近及奇异值分解技术求出电场与频率的有理函数解析表达式,从而获得频带内的S参数。数值计算结果与已有结果吻台良好,并且与传统FDFD法相比,计算效率提高很多。