时域有限差分法的收敛性

本文通过计算实例讨论了时域有限差分法的收敛性问题。计算了在平面波照射下无限长介质柱中的电磁场分布。把不同空间和时间步长时的计算结果,与用解析法所获得的结果进行比较,证明时域有限差分法有较好的收敛特性。对具有不同空间分辨率的人体二维非均匀块状模型中吸收电磁能量分布的计算表明,在高度非均匀介质中的场分布,仍然保持较好的收敛性。这些讨论从一个侧面提供了选取网格步长的依据。     

一种基于积分求导(DQ)的时域有限差分法(TD-FD)

本文提出用DQ(Differential Quadrature)将Maxwell方程中的部分偏微分进行近似计算,从而减少时域有限差分法(TD-FD)算法中的网络节点数目,节省计算机的内存,提高TD-FD的分析效率.     

一种分析微带贴片天线的辛时域有限差分方法

文中研究了在时间上采用5级4阶差分、空间上采用4阶差分的高阶辛时域有限差9（SFDTD）数值方法。给出其三维差分公式．将吸收边界条件应用于微带天线的计算中，计算了微带贴片天线的回波损耗及输入阻抗等．计算结果证明，该方法的精确性和正确性．     

时域有限差分法分析微带不连续性

本文采用时域有限差分（TD－FD）法分析微带不连续性问题，在研究分析方法的同时，着重分析了微带双分路线，同时还对微带阶梯，微带间隙和微带终端开路进行了分析，准确地求出了它们的散射参数，显示了TD－FD方法在解决微波电路问题上具有广泛的应用前景。     

时域有限差分法对不连续微带线的分析

不连续微带线的特性以前已由几种全波方法计算得到.本文涉及的时域有限差分法(FDTD方法)是一种独立的算法,是计算微波相关器件频域特性较新的方法.本文的目的是验证用FDTD方法分析电路组成元件特性的有效性.     

基于时域有限差分法的广义传输矩阵的研究

文章研究了基于时域有限差分法的时域广义传输矩阵方法,时域广义传输矩阵在包含散射体的惠更斯等效面上计算和提取,通过时域积分方程和时域有限差分法的混合应用计算得出。本文同样给出了一个在等效面上RWG基函数和FDTD网格上的变换算法。基于时域有限差分法的时域广义传输矩阵方法比基于时域步进法（MOT）和积分方程的广义传输矩阵方法更加稳定。     

时域有限差分法的Matlab仿真

介绍了时域有限差分法的基本原理，并利用Matlab仿真，对矩形波导谐振腔中的电磁场作了模拟和分析。     

时域有限差分法及在光电子学中的应用（一）

时域有限差分法是近几年来发展很快的一种求解电磁问题的数值方法。这种方法适应性强，所用计算机存储单元少，已在许多领域得到大量应用。介绍了时域有限差分法的基本原理和在光电子学中的一些应用。     

一种提高内存使用效率的时域有限差分算法

证明了即使在无源区域,局部一维时域有限差分法（LOD-FDTD）所给出的电磁场量也不满足零散度关系,推导了该散度关系的具体表达式。基于该非零散度关系和麦克斯韦旋度方程,将LOD-FDTD法与减缩时域有限差分法（R-FDTD）相结合,得到一种新的局部一维减缩时域有限差分法（LOD-R-FDTD）。该方法不仅具有LOD-FDTD方法的优势,计算公式简单,消除了CFL稳定条件对时间步长的限制,而且与LOD-FDTD相比平均节约了1/3内存使用量。通过仿真计算与其他方法对比,证明了LOD-R-FDTD方法的准确性和有效性。     

金属透镜的色散时域有限差分法研究

为克服传统时域有限差分法(FDTD)不能计算色散材料的困难,给出了一种基于Drude模型的色散FDTD算法,并推导出具体的差分公式。将该方法用于模拟金属透镜的聚焦功能,结果与已有理论吻合。本文方法完全适用于分析电导率与频率有关的各种色散材料所构建的光波导。     

A novel finite-difference time-domain wave propagator

A novel time-domain wave propagator is introduced. A two-dimensional (2-D) finite-difference time-domain (FDTD) algorithm is used to analyze ground wave propagation characteristics. Assuming an azimuthal symmetry, surface, and/or elevated ducts are represented via transverse and/or longitudinal refractivity and boundary perturbations in 2-D space. The 2-D FDTD space extends from x=0 (bottom) to x→∞ (top), vertically and from z→-∞ (left) to z→∞ (right), horizontally. Perfectly matched layer (PML) blocks on the left, right, and top terminate the FDTD computation space to simulate a semi-open propagation region. The ground at the bottom is simulated either as a perfectly electrical conductor (PEC) or as a lossy second medium. A desired, initial vertical field profile, which has a pulse character in time, is injected into the FDTD computation space. The PML blocks absorb field components that propagate towards left and top. The ground wave components (i.e., the direct, ground-reflected and surface waves) are traced longitudinally toward the right. The longitudinal propagation region is covered by a finite-sized FDTD computation space as if the space slides from left to right until the pulse propagates to a desired range. Transverse or longitudinal field profiles are obtained by accumulating the time-domain response at each altitude of range and by applying the discrete Fourier transformation (DFT) at various frequencies     

A finite-difference time-domain method applied to anisotropicmaterial

The popularity of the finite-difference time-domain (FDTD) method stems from the fact that it is not limited to a specific geometry and it does not restrict the constitutive parameters of a scatterer. Furthermore, it provides a direct solution to problems with transient illumination, but can also be used for harmonic analysis. However, researchers have limited their investigation to materials that are either isotropic or that have diagonal permittivity, conductivity, and permeability tensors. The authors derive the necessary extension to the FDTD equations to accommodate nondiagonal tensors. Excellent agreement between FDTD and exact analytic results is obtained for a one-dimensional anisotropic scatterer     

A finite-difference time-domain beam-propagation method for TE- and TM-wave analyses

The application of the existing time-domain beam-propagation method (TD-BPM) based on the finite-difference (FD) formula has been limited to the TE-mode analysis. To treat the TM mode as well as the TE mode, an improved TD-BPM is developed using a low-truncation-error FD formula with the aid of the alternating-direction implicit scheme. To improve the accuracy in time, a Pade (2,2) approximant is applied to the time axis. Although the truncation error in time is found to be O(/spl Delta/t/sup 2/), as in the case of the Pade (1,1) approximant, this method allows us to use a large time step. A substantial reduction in CPU time is found when compared to the conventional method in which a broadly banded matrix is solved by the Bi-CGSTAB. The effectiveness in evaluating the TE- and TM-mode waves is shown through the analysis of the power reflectivity from a waveguide facet. This method is also applied to the analysis of a waveguide grating. The accuracy and efficiency of the TD-BPM are assessed in comparison with the finite-difference time-domain method.     

A finite-difference time-domain method for solving electromagneticproblems with bandpass-limited sources

The complex-envelope representation of bandpass-limited signals is used to formulate a bandpass-limited vector wave equation and a new finite-difference time-domain (FDTD) scheme that solves the bandpass-limited vector wave equation is presented. For narrow-band electromagnetic systems, this new method allows the time step to be several orders of magnitude larger than current FDTD formulations while maintaining an amplification factor equal to one. Example results obtained by this method are presented and compared with analytic solutions     

A semivectorial finite-difference time-domain method (optical guided structure simulation)

A semivectorial finite-difference time-domain method (FDTD) that solves the vector wave equations for the transverse electric fields is presented and validated. By taking into consideration the boundary conditions for the transverse, electric fields in the finite-difference scheme, the polarization effect of the electromagnetic waves can be modeled. In comparison with the full vector FDTD, the present approach requires less memory and is more computational efficient. The method is validated by a comparison with the exact analytical solutions as well as the full vector FDTD results and is shown to be very accurate.<>     

A subgridding method for the time-domain finite-difference methodto solve Maxwell's equations

A modification to the time-domain finite-difference method (TDFDM) that uses a variable step size is investigated. The entire computational volume is divided into a coarse grid with a large step size. A fine grid with a small step size is introduced only around discontinuities. The corresponding time increments are related to the spatial increments with the same ratio in order to minimize the numerical dispersion. The fields within the coarse and fine grids are found using the TDFDM, while an interpolation in space and time is utilized to calculate the tangential electric field on the coarse-fine grid boundary. This subgridding decreases the required computer memory and therefore expands the capability of the TDFDM. The technique is shown to be numerically stable and does not entail any extra numerical error. The method is applied to the calculation of waveguides and microstrips     

A finite-difference time-domain method for the design and analysisof guided-wave optical structures

A CAD tool employing the finite-difference time-domain (FDTD) algorithm is developed for the design and analysis of optical waveguide structures. The basic formulation of the algorithm is given, and practical conditions for its application are briefly outlined. The accuracy of the numerical scheme is investigated through a study of a canonical parallel-slabs coupling structure. Both the coupling length and the field distribution are in good agreement with results in the literature. The use of the method is illustrated by an analysis of a directional coupler     

Crosstalk noise modeling of multiwall carbon nanotube (MWCNT) interconnects using finite-difference time-domain (FDTD) technique

This paper presents an accurate and efficient model for the transient analysis of multiwall carbon nanotubes (MWCNT) using finite-difference time-domain (FDTD) method. The proposed model can be essentially used to analyze the functional and dynamic crosstalk effects of coupled-two MWCNT interconnect lines. Using the proposed model the voltage and current can be accurately estimated at any point on the interconnect line and furthermore, the model can be extended to coupled-n interconnect lines with a low computational cost. Crosstalk induced propagation delay, peak voltage, and its timing instance are measured using the proposed model and validated by comparing it to the HSPICE simulations. Over a random number of test cases it is observed that the average error in estimating the noise peak voltage on a victim line is less than 1%. The proposed model is extremely useful for accurate estimation of crosstalk induced performance parameters of MWCNT interconnects.     

A conformal mesh-generating technique for the conformal finite-difference time-domain (CFDTD) method

This article presents an efficient conformal-mesh generating technique suitable for the conformal finite-difference time-domain (CFDTD) technique. We describe the mesh generation for different types of objects, including planar structures (patch antennas and microwave circuits), as well as for arbitrary three-dimensional structures created by using AutoCAD, GID, or other commercial solid modelers. The versatility of the mesh-generation tool is illustrated through several examples.     

A novel subgridding scheme based on a combination of thefinite-element and finite-difference time-domain methods

A simple and versatile local mesh refinement scheme, based on the hybridization of the finite-element (FE) and the finite-difference time-domain (FDTD) algorithms, is presented. The scheme achieves considerable flexibility in subgridding by using a transition region between the coarse and fine FDTD grids, meshed according to an unstructured grid, and solved by means of the FE method in the TD. An interpolation scheme in the time domain, which allows the use of different time steps in the coarse and fine mesh regions, is included in the paper