Modelling of coaxial-fed microstrip patch antenna by finite difference time domain method

A direct three-dimensional finite-difference time-domain (FDTD) method is applied to coaxial-fed microstrip antennas. The model is shown to be an efficient and accurate tool for modelling coaxial-fed structures. The reflection coefficient can be determined from the simulated time-domain wave that is reflected down the coaxial line. Excellent agreement over a wide frequency range is shown in two cases between the measured and FDTD derived results.<>     

FDTD法计算高频单极天线特性

用时域有限差分法（Ｆｉｎｉｔｅ Ｄｉｆｆｅｒｅｎｃｅ Ｔｉｍｅ Ｄｏｍａｉｎ Ｍｅｔｈｏｄ）计算天线阻抗特性,可以使用不同的激励方式,文章比较了采用不同激励方式时,天线的输入阻抗。文中的主要内容是将表面阻抗法用于ＦＤＴＤ中,计算架设在介质平面上单极天线的辐射特性,并用ＦＤＴＤ法计算了介质平面上铺设不同尺寸的导体平面时,单极天线的输入阻抗随导体平面尺寸变化的特性。     

基于并行FDTD方法分析表面等离子波导的特性

设计了一种双L形表面等离子体矩形环谐振器波导,采用并行时域有限差分方法,对这种波导的传输特性随几何结构参数的依赖关系进行了分析.计算结果表明通过改变输入/输出光波导的结构参数,可以调节该波导的消光比和频率选择特性.该波导结构能够有效地抑制后向辐射干扰并且大幅度地提高其场消光比,这使得此类谐振器结构更具有功能性.     

新型分裂步长时域有限差分法

提出一种新型的分裂步长时域有限差分(NSS-FDTD)法,并对其数值色散进行分析。该方法基于Split-Step方案和Crank-Nicolson方案,采用新的矩阵分解形式,与传统的FDTD算法、SS-FDTD算法相比,减少了计算复杂度。新型算法的推导程序简单,且具有良好的数值色散特性,还加入了一阶Mur吸收边界条件,给出一阶Mur吸收边界差分方程。将数值实验的结果和传统FDTD方法及理论值进行比较,数值结果一致性较好。     

Conformal hybrid finite difference time domain and finite volumetime domain

A hybrid method that combines the finite difference time domain (FDTD) and the finite volume time domain (FVTD) methods is presented. The FVTD, based on a conformal and unstructured grid is used in the near vicinity of the surface of a scatterer, and the FDTD is used to model the fields in the surrounding area. The two are coupled together through interpolation. The vertex-based FVTD allows for more convenient and accurate interpolations than a conformal FDTD method. The hybrid method is validated through two examples-the scattering by a PEC cube and sphere-by comparison with the direct FDTD solution, and with an exact Mei series solution for the spherical case     

平面波在时域有限差分法中的引入方法研究

基于角点延迟的思想,研究了时域有限差分(FDTD)法中,两种在连接边界上引入平面波的方法--一维平面波推进法和解析法.仿真结果表明:一维平面波推进法与解析法同样有效;一维平面波推进法很大程度上抵消了FDTD法的数值色散误差,溢出波较少,而解析法出现了较多的溢出波;使用一维平面波推进法时,减小网格尺寸能够进一步减小溢出波...     

细线结构时域电场积分方程的有限差分求解

提出一种求解基于细线结构的时域电场积分方程 ( TDEFIE)的方法 -有限差分方法。与传统求解时域电场积分方程的时域矩量法相比 ,该方法易于数值实现。文中还利用该方法研究了电磁辐射、散射的三个经典问题 ,并将结果与时域矩量法的结果进行了比对 ,研究表明 ,该方法求解细线结构的 TDEFIE非常有效。     

3D crank-nicolson finite difference time domain method for dispersive media

The unconditionally stable Crank-Nicolson finite difference time domain (CN-FDTD) method is extended to incorporate frequency-dependent media in three dimensions. A Gaussian-elimination-based direct sparse solver is used to deal with the large sparse matrix system arising from the formulation. Numerical results validate and confirm that the scheme is unconditionally stable for time steps over the Courant-Friedrich-Lewy limit of classical FDTD.     

Analysis of electromagnetic radiation from shaped-end radiatorsusing the finite difference time domain method

The finite difference time domain (FDTD) technique is a popular method for analyzing electromagnetic scattering, radiation, and penetration problems. Several authors have recently applied the FDTD method to antenna radiation problems. To date, the antenna structures considered have been wire and conical monopole antennas, rectangular waveguides, pyramidal horn antennas, and microstrip antennas. Results from these analysis have been in the form of normalized field patterns and no results showing absolute gain have been presented. The article demonstrates the first staircased application of the FDTD method to the analysis of radiation from circular waveguides and other shaped-end radiators. Results of absolute gain versus angle are shown for a straight-cut circular waveguide and for two different shaped-end radiators. All FDTD analyses are full three-dimensional computations and are compared in each case with measured data     

A new stable hybrid three-dimensional generalized finite difference time domain algorithm for analyzing complex structures

In this paper, we propose a new stable hybrid, three-dimensional (3-D), generalized finite difference time domain algorithm-formulated by using of the cell method (CM) (a finite volumes type method)-designed to analyze objects with fine details without using very small time steps dictated by the Courant condition. The new algorithm is an extension to the 3-D cases of an analogous hybrid two-dimensional algorithm, also formulated by the CM, and presented earlier by the authors in a previous publication. We carry out a detailed analysis of the stability of the proposed algorithm, paying special attention to the phenomenon of late time instabilities. Finally, the results of some numerical tests are provided to show the absence of instabilities and the efficiency of the hybrid algorithm.     

Cross-shaped dielectric resonator antenna analysis using conformalfinite difference time domain method

A cross-shaped dielectric resonator antenna, designed for circular polarisation, is analysed via the conformal finite difference time domain technique. The conformal technique, which can handle canted surfaces that do not conform to the Cartesian system of co-ordinates, is used to generate accurate results with a relatively coarse mesh, e.g. it is shown that the conformal FDTD offers a 2:1 advantage over staircasing, without compromising accuracy     

Coupling of methods: finite difference time domain and asymptoticmethods

The authors describe a hybrid method intended for the resolution of the electromagnetic diffraction of structures of very different sizes. The problem to be solved is divided into two subdomains: a first domain where a `rigorous formulation' method analyses the radiation of small elements, and a second domain where an `asymptotic' method analyses the diffraction on the edges of large elements     

Fast division-free parallel structure for convolution perfectly matched layer in finite difference time domain method

Parallel acceleration of convolution perfectly matched layer(CPML) algorithm suffers from massive division operation which is widely accepted as one of the most expensive operations for the equipment such as graphic processing unit(GPU), field programmable gate array(FPGA) etc. In pursuit of higher efficiency and lower power consumption, this article revisited the CPML theory and proposed a new fast division-free parallel CPML structure. By optimally rearranging the CPML inner iteration process, all the division operators can be eliminated and replaced by recalculating the related field updating coefficients offline. Experiments show that the proposed division-free structure can save more than 50% arithmetic instructions and 25% execution time of the traditional parallel CPML structure without any accuracy loss.     

Analysis of periodic structures via a time-domain finite-element formulation with a Floquet ABC

An accurate absorbing boundary condition (ABC) is presented for three-dimensional time-domain finite-element (FEM-TD) analysis of infinitely periodic structures. The proposed ABC serves to truncate the computational domain in the nonperiodic directions and it is highly effective to absorb both the fundamental and the higher order Floquet modes. The formulation is applicable both for scattering and radiation analysis. Validation results are presented that demonstrate the ability of the FEM-TD to obtain highly accurate results over a broad frequency band that includes frequencies where a higher order Floquet mode is propagating (nonevanescent).     

ANALYSIS OF OPEN MICROSTRIP STRUCTURES BY USING DIAKOPTIC METHOD OF LINES COMBINED WITH PERIODIC BOUNDARY CONDITIONS

This paper presents the analysis of open microstrip structures by using diakoptic method of lines (ML) combined with periodic boundary conditions (PBC). The parameters of microstrip patch are obtained from patch current excited by plane wave. Impedance matrix elements are computed by using fast Fourier transform(FFT), and reduced equation is solved by using diakoptic technique. Consequently, the computing time is reduced significantly. The convergence property of simulating open structure by using PBC and the comparison of the computer time between using PBC and usual absorbing boundary condition (ABC) show the validity of the method proposed in this paper. Finally, the resonant frequency of a microstrip patch is computed. The numerical results obtained are in good agreement with those published.     

A conformal finite difference time domain technique for modelingcurved dielectric surfaces

In this paper, we present a simple yet accurate conformal Finite Difference Time Domain (FDTD) technique, which can be used to analyze curved dielectric surfaces. Unlike the existing conformal techniques for handling dielectrics, the present approach utilizes the individual electric field component along the edges of the cell, rather than requiring the calculation of its area or volume, which is partially filled with a dielectric material. The new technique shows good agreement with the results derived by mode matching and analytical methods     

Hybrid technique combining finite element, finite difference andintegral equation methods in time domain

A new hybrid time domain method is presented which combines three well-known numerical techniques. i.e. the finite difference time domain (FDTD) method, finite element (FE) method and method of moments (MoM). The hybrid scheme has been designed to handle complex geometries comprising arbitrary thin-wire structures and inhomogeneous dielectric regions the shape of which can also be arbitrary. Numerical results are presented which illustrate the accuracy of the method