FDTD analysis of electromagnetic wave radiation from systemscontaining horn antennas

The application of the finite-difference time-domain (FDTD) method to various radiating structures is considered. These structures include two- and three-dimensional waveguides, flared horns, a two-dimensional parabolic reflector, and a two-dimensional hyperthermia application. Numerical results for the horns, waveguides, and parabolic reflectors are compared with results from using the method of moments (MM). The results for the hyperthermia application are shown as extensions of the previously validated models. This new application of the FDTD method is shown to be useful when other numerical or analytic methods cannot be applied     

Evaluation of antenna radiation Q using FDTD method

A new and simple method is proposed for determining the radiation Q of an antenna using the finite difference time domain (FDTD) method. The numerical results are compared with analytical formulas and good agreement is reported.     

Liquid crystal electromagnetic radiation monitor

Liquid Crystals having color play centered at different temperatures are arranged on metal coated and nonmetal coated dielectric substrates and used to monitor electromagnetic radiation. While both substrates respond to changes in ambient temperature conditions, the metallized substrate will also have temperature changes due to absorbed radiation. The temperature-dependent light scattering properties of the liquid crystals are used as both the temperature measuring mechanism and the indicating mechanism, with the difference between the temperature indications of the two substrates being a measure of the radiation. An experimental model that measures radiation of 1 to 15 mW/cm2 at 2.45 GHz is described.     

Novel FDTD simulation method using multiple-analysis-space for electromagnetic far field

Wide-band undesired electromagnetic noise near electronic systems, which includes small noise source like the printed circuit board (PCB), is a current problem in the field of electromagnetic interference. However, the estimation method for the electromagnetic noise near a system under test has not been established. This paper proposes a newly developed estimation method of the electromagnetic noise for a wide area, from near to far field, using the finite difference time-domain (FDTD) method. The proposed FDTD simulation method is an estimation technique for near to far field with multiple analysis spaces (MAS). The MAS has an internal analysis space (IAS) and an external analysis space (EAS). The analysis near a radiation source can be calculated in the IAS. The EAS is the outside space from IAS, which is for calculation of the far field. It is expected that the proposed FDTD method by MAS (FDTD-MAS) decrease in the calculation cost in terms of computational time and memory costs, especially for estimation of radiation from PCB. The principle procedure of the FDTD-MAS method is described in the first part of this paper. As example of advantages of the calculation and confirmation of the calculation accuracy, the electric field distributions radiated from a 1-GHz half-wavelength dipole antenna in an IAS of 0.3/spl times/0.3 m/sup 2/ area and an EAS of 7/spl times/7 m/sup 2/ area are used as examples. When the cell size ratio of IAS to EAS is changed from 6 to 20, the FDTD and theoretical values show good agreement. It is indicated that the FDTD-MAS simulation method is one of the most powerful tools for the estimation of electromagnetic noise from near field to far field from small and thin source.     

基于石墨烯一维太赫兹光子晶体电磁特性研究

采用时域有限差分(Finite Difference Time Domain FDTD)和表面边界条件对单层石墨烯的太赫兹电磁特性进行研究.首先计算了其反射和透射系数, 并与解析解对比验证了该理论的正确性.接着研究了一维光子晶体表面石墨烯在太赫兹光谱范围的吸收.通过改变模型中石墨烯的位置, 得到了一维石墨烯吸收特性与石墨烯位置的关系.结果表明:当石墨烯位于光子晶体表面时, 由于石墨烯和间隔层在光子晶体表面构成了表面缺陷, 从而导致光的局域化, 这种局域化增强了石墨烯对太赫兹范围光的吸收.     

基于FDTD方法的同轴电缆孔缝辐射效应研究

利用时域有限差分法(FDTD)研究了同轴电缆传输数字脉冲信号时的孔缝辐射效应。文中首先推导了三维柱坐标系下完全匹配层(PML)的差分表达式，并给出保证其解稳定性的更为严格的时间步长公式。然后利用FDTD法分析了数字信号经同轴电缆孔缝的辐射效应，对孔缝内外的电磁场及其远场进行了数值分析和计算。处理孔缝边界时，用级数展开和积分方程得到金属拐角处电磁场的近似解。最后对结果进行了分析。     

基于GPU的并行FDTD方法在二维粗糙面散射中的应用

利用显卡(Graphics Processing Unit, GPU)加速时域有限差分(Finite-Difference Time Domain, FDTD)法计算二维粗糙面的双站散射系数, 介绍了FDTD的理论公式以及计算模型.采用各向异性完全匹配层(Uniaxial Perfectly Matched Layer, UPML)截断FDTD计算区域.重点讨论了基于GPU的并行FDTD计算粗糙面双站散射系数的并行设计方案计算流程.在NVIDIA GeForce GTX 570显卡上获得了50.7×的加速比.结果表明:通过对FDTD计算粗糙面散射问题的加速, 极大地提高了计算效率.     

Efficient analysis of electromagnetic radiation from microstrip antenna using volume-surface current contunuity method

The Volume-Surface Current Continuity Method (VSCCM) is presented to analyze electromagnetic radiation from microstrip antenna. The microstrip antenna is discretized into small triangular patches on conducting surface and tetrahedral volume cells in dielectric region. The Method of Moments (MoM) is applied to solve the integral equation. An equation contains the restriction relation between the volume and surface current coefficient is derived from the current continuity equation at those parts where the conducting surface is in contact with the dielectric material. A simple equivalent strip model is introduced in the treatment of the feeding probe in VSCCM. The VSCCM can reduce the unknowns required to be solved in MoM, as well as the condition number of the matrix equation. Numerical results are given to validate the accuracy and efficiency of this method.     

场路结合法分析设备电磁辐照效应

电子设备机壳内部往往会内置多层印制电路板,外界电磁干扰很可能通过设备的外接导线进入设备内部进而对电路板造成损坏。针对这种情况,采用全波分析法获得受干扰设备的相关参数,利用该参数建立等效源模型;等效电路法分析内部电路板上电路的电磁特性。通过全波分析法和等效电路法相结合的方式来分析外界电磁干扰进入设备内部时所造成的影响,为处于高频电磁干扰环境中的电路工作特性研究提供新思路和参考。     

基于FDTD的太赫兹光导天线三维辐射特性计算方法

光导天线是目前产生和探测太赫兹波最常用的辐射源之一,在太赫兹成像、光谱检测等诸多领域有着广泛的应用前景。本文介绍了基于时域有限差分(FDTD)的太赫兹光导天线三维辐射特性计算方法,在分析光导天线辐射原理的基础上阐述了半导体漂移电流、扩散电流对电场及磁场的作用,并根据实际运用情况对漂移方程、连续性方程进行简化,最终求得电流密度、电场、磁场的迭代方程,给出了光导天线辐射特性计算流程。     

用数值方法分析室内电磁环境

提出了利用数值方法计算钢筋混凝土墙包围的室内电磁环境的方法.在该方法中,首先要将整个墙体的复杂结构分成若干小的单元块.对于每个小的单元块而言,针对其具体结构的细节计算其电磁特性,并记录在相对应的特性矩阵中.基于这些矩阵建立表面积分方程进行求解,将大大提高计算的效率.     

基于高阶时域有限差分算法的电磁波传播计算

利用FDTD(2,4)高阶时域有限差分(Finite-Difference Time-Domain,FDTD)算法并结合滑动窗口的思想,对电磁波传播特性进行了仿真计算. 采用的高阶FDTD算法在空间上达到四阶精度,与二阶精度的传统FDTD算法相比,在相同每波长采样数的条件下,数值色散误差能得到进一步的减少. 在源脉冲传播较长距离时,数值色散的减少使得时域下脉冲扩展现象得到改善,滑动子窗口仍然能包含着激励源脉冲的全部信息,从而可更加准确地计算长距离电波传播特性. 另外,在相同的数值色散误差容限下,每波长采样数比传统二阶FDTD方法有所减少,从而节省存储空间,加快计算速度.     

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     

光子晶体波导的FDTD分析

介绍了光子晶体波导的原理,然后运用时域有限差分方法(FDTD法)分析了二维光子晶体波导的传输特性,最后运用Matlab语言实现了二维光子晶体波导的仿真,使用的是TM模.     

基于移位算子法双负介质散射的FDTD分析

双负介质的介电系数和磁导系数均为频率的函数,使本构关系在时域成为卷积关系,这就给应用时域有限差分(FDTD)方法计算双负介质中波的散射和传播带来困难.文中以相对磁导系数为例,引入Padé近似和离散时域移位算子,推导了处理双负介质本构关系的移位算子法.移位算子法数值仿真双负介质负折射效应的结果与文献辅助差分方程法的结果吻合,证明了算法的有效性.最后,用移位算子法计算了金属柱覆盖不同参数双负介质时的后向散射,探讨双负介质在隐身方面的应用前景.     

FDTD modeling of common-mode radiation from cables

Radiation from cables attached to printed circuit boards and shielding enclosures is among the primary concerns in meeting FCC Class A and B limits. The finite-difference time-domain (FDTD) method can be employed to model radiation from printed circuit boards and shielding enclosures with complex geometries, but difficulties in modeling wires and cables of arbitrary radii are encountered. Modeling the wire by setting the axial component of the electric field to zero in the FDTD method results in an effective wire radius that is determined by the mesh discretization. Neglecting the wire radius in applications, such as electromagnetic interference (EMI) or printed circuit board modeling, may result in gross errors because near-field quantities are typically sensitive to wire thickness. Taflove et al. (1988) have developed a subcellular FDTD algorithm for modeling wires that has been shown to work well for plane wave scattering. The method uses a quasistatic field approximation to model wires with a well defined radius independent of the mesh dimensions. The wire model is reviewed and investigated for application to common-mode radiation from cables attached to printed circuit boards, where the source is often a noise voltage at the connector. Also investigated is energy coupling to attached cables through enclosure apertures resulting in common-mode radiation from the cable. The input impedance for a center-fed dipole antenna, as well as a monopole connected to a conducting half-sheet, is computed with FDTD methods and compared to moment method input impedance results. A simulation of a shielding enclosure with an attached cable demonstrates the utility of FDTD analysis in modeling common-mode radiation     

FDTD分析准八木天线的算法实现

介绍时域有限差分（FDTD）法计算准八木天线驻波比的算法实现方法。文中利用模型描述文件对天线进行了建模和网格划分;将各向异性完全匹配层（UPML）吸收边界分区编写,并利用区域的对称性简化了程序;采用带内阻的电压源作为激励源;最后从总电压中分离出入射电压和反射电压,得到了准八木天线的驻波比。实际制作了一个准八木天线并进行了测试,计算结果与实测结果基本一致,表明该实现方法是正确和有效的。     

Analysis of electromagnetic scattering from anisotropic cylindrical structures using state space method

Scattering of the electromagnetic waves from anisotropic cylindrical structures (ACS) is investigated using an exact and analytical frequency domain method in the most general case. The state space approach is used for analyzing of wave propagation in cylindrical structures for the first time. The validity of the proposed method is verified for the anisotropic cylindrical structures which have closed-form solutions. Comparing the results obtained by closed-form solution, the proposed approach and other commonly used methods in literature shows that the method is accurate, fast and simple. The presented study is covered all practical considerations in the field of electromagnetic scattering from ACS's such as polarization and incident angle of excitations, the geometry and configuration of the structure. This comprehensiveness is one of the biggest advantages of the investigation. Regarding the applications of the state space method in parameters retrieval of planar structures, the present study can be effective as the first and basic step in opening a new way toward further studies on inverse scattering of the cylindrical structures consisting complex media.     

Surface integral representation radiation boundary condition forthe FDTD method

A radiation boundary condition for the finite-difference-time-domain (FDTD) method is presented. It is based on a time-domain integral representation of the electromagnetic fields outside the calculation volume in terms of the known fields on a surface surrounding that volume. Numerical evaluation of the method shows that its performance is superior to that of existing radiation boundary conditions     

FDTD方法在磁共振射频线圈仿真中的应用

本文提出了磁共振射频线圈电磁场仿真计算的FDTD方法,并对该方法中的仿真计算稳定性和边界吸收条件等关键技术的实现进行了详细阐述.利用这种方法,本文对磁共振鸟笼线圈的电磁场进行仿真计算分析,并给出了电磁场分布的仿真计算结果,仿真结果与鸟笼线圈的实际电磁场分布相吻合.