横电磁波传输室谐振频率的有限元分析

采用三维有限元法分析了TEM传输室的高次模截止频率和谐振频率.在有限元分析软件ANSYS下进行了建模求解,提供了一种快速、准确求解TEM传输室谐振频率的有效方法.通过实验分析,证实了对场分布影响较大的第一阶谐振频率是TE101模,TE101模的谐振频率是TEM传输室的上限使用频率.     

三导体TEM cell的场分布研究

本文采用时域有限差分（FDTD）法模拟了电磁波在三导体模电磁波室（T－TEM cell）中的传播,给出了T－TEM室在不同芯板加载情况下的横向场分布和纵向均匀性,并对其三维场分布进行了实际测量;将理论计算值与实测值进行比较后证实,芯板接地状况对场分布具有较大的影响,所得结果对T－TEM室的工程设计具有重要的指导意义。     

一种圆锥形横电磁波传输室的分析

给出一种新型横电磁波传输室－圆锥菜横电磁波传输室,并在球坐标系下采用时域有限差分（FDTD）法对其场分布进行计算,分析了高阶模的影响,确定了传输室的上限工作频率范围。分析和计算结果表明,圆锥形横电磁波传输室的电场极化方向可任意改变,上限工作频率可达4GHz,具有广泛的应用前景。     

吉赫横电磁波传输室传输特性的宽频带分析

吉赫横电磁波传输室(GTEMcell)上限工作频率可达几个吉赫,因而在电磁兼容测量中得到越来越广泛的重视和应用。本文在非正交坐标系下采用FDTD(时域有限差分)法求解电磁波在GTEMcell中的传输特性,给出了GTEMcell中TEM模的横向分布和纵向分布,分析了高阶模对场分布均匀性的影响,由此确定了GTEMcell的上限工作频率范围。计算及分析结果对GTEMcell的设计和使用具有重要意义。     

吉赫横电磁波传输室传输特性的宽频带分析

吉赫横电磁波传输室（ＧＴＥＭ ｃｅｌｌ）上限工作频率可达几个吉赫,因而在电磁兼容测量中得到越来越广泛的重视和应用。本文在非正效坐标系下采用ＦＤＴＤ（时域有限差分）法求解电磁波在ＧＴＥＭ ｃｅｌｌ中的传输特性,给出了ＧＴＥＭ ｃｅｌｌ中ＴＥＭ模的模向分布和纵向分布,分析了高阶模对场分布均匀性的影响,由此确定了ＧＴＥＭ ｃｅｌｌ的上限工作频率范围。计算及分析结果对ＧＴＥＭ ｃｅｌｌ的设计和使用具有重要     

一种圆锥形横电磁波传输室的分析

给出一种新型横电磁波传输室－圆锥形横电磁波传输室,并在球坐标系下采用时域有限差分(FDTD)法对其场分布进行计算,分析了高阶模的影响,确定了传输室的上限工作频率范围。分析和计算结果表明,圆锥形横电磁波传输室的电场极化方向可任意改变,上限工作频率可达4GHz,具有广泛的应用前景。     

基于遗传算法的横电磁波传输室芯板优化设计

采用遗传算法,对横电磁波传输室(TEM CELL)内的芯板结构参数做了优化,优化结果增加了横电磁波传输室(TEM CELL)的测试区域,提高了传输室的效费比。同时也验证了遗传算法解决此类问题的有效性。     

TEM传输室置入金属EUT后场分布的边界元分析

横电磁波传输室广泛应用于电磁兼容试验中，当置入受试设备后，其中的场分布会发生扰动。本文采用边界元法分析了横电磁波传输室中置入金属箱体的受试设备后场分布的规律，对受试设备所受暴露场的场强进行了计算，并提出了具体的估算方法。对空载时横电磁波传输室的场分布进行了测量，测量结果证实了计算方法的正确性。     

横电磁波传输室的性能评估

为了对横电磁波传输室的性能做出评估,分别使用HFSS仿真软件和测试仪器对TEM Cell的电压驻波比和插入损耗进行了分析,通过两种方法得到的结论符合性较好,证明了仿真模型的有效性.通过仿真分析得到了TEM Cell的电磁场分布,找到了TEM Cell中场分布均匀的区域,为今后的实际使用提出了建议.     

随钻中继式电磁波传输技术及应用研究

针对随钻条件下无线电磁波传输技术信号衰减大、传播距离短、信号频率低以及传输速率慢的难题,文章设计了基于准横电磁波（Transverse Electromagnetic Wave,TEM）激励模式的随钻中继式电磁波传输技术。该技术以钻杆作为传输载体,将电磁波在井内的随钻传输模型类比同轴线传输模型,通过使用多组载波频率,在提高传输速率的同时,利用中继接力扩展传输距离。该技术已通过不同地层环境的现场验证,是井下数据传输未来发展的重要方向。     

The theory of chirowaveguides

The theory of chirowaveguides is discussed, and their salient features are analyzed. It is shown that the Helmholtz equations for the longitudinal components of electric and magnetic fields in chirowaveguides are always coupled and that, consequently, in these waveguides individual transverse electric (TE), transverse magnetic (TM), or transverse electromagnetic (TEM) modes cannot be supported. As an illustrative example, the parallel-plate chirowaveguide is analyzed in detail and the corresponding dispersion relations, cutoff frequencies, and propagating and evanescent modes are obtained. In the dispersion (Brillouin) diagram for a chirowaveguide, three regions are identified: the fast-fast-wave region, the fast-slow-wave region and the slow-slow-wave region. For each of these regions, the electromagnetic field components in a parallel-plate chirowaveguide are analyzed and the electric field components are plotted. Potential applications of chirowaveguides in integrated optical devices, communications systems, and printed circuit antennas are mentioned     

Finite-element analysis of a triple-TEM cell

The triple-TEM (TTEM) cell offers the possibility of alternative exposures of the electric field on the equipment under test in one setup. Traditional TEM cell design approaches cannot be applied to the TTEM cell because of the special geometric arrangement of the inner conductors. Several important characteristics of the TTEM cell, such as TEM field distributions, characteristic impedance, and cutoff frequencies of higher order modes (TE and TM) are analyzed by using the finite-element method (FEM). The high-frequency performance of the TTEM cell is investigated using a novel FEM approach-the Laplace domain finite-element method (LDFEM). Numerical results obtained thereupon are useful in the engineering design of the TTEM cell     

Electromagnetic Fields in Complementary and Self-Complementary Structures

Electromagnetic fields are analyzed in complementary and self-complementary structures. As is well known, Maxwell's equations exhibit a complementary (duality) symmetry between the electric and magnetic fields. Self-complementary field solutions (when these exist) on self-complementary structures have particular properties of constant impedance (resistance) associated with certain pure traveling wave fields. The contribution of this paper is that it rigorously treats the electromagnetic field in a self-complementary waveguide. It shows a self-complementary field solution is a pure traveling wave. A particular waveguide structure is selected that illustrates circumstances when a self-complementary field solution fails to exist in a self-complementary structure. A computer model was developed to analyze a family of waveguide structures that differ only in an aspect ratio parameter, an aspect ratio of 1.0 corresponding to the self-complementary case. The original structures and the corresponding complementary structures are analyzed independently. Results are presented for a wide range of frequencies and aspect ratios. At low frequencies, when only one TEM mode propagates, field solutions for the input TEM mode exhibit discontinuous behavior as the aspect ratio approaches one from above and below. In this frequency range, no time harmonic self-complementary field solution exists for the precisely self-complementary waveguide structure.     

加载横电磁传输室中的电场分布计算

用“准静脉法”研究了当工作频率远低于截止频率时,放置于横电磁传输室中的被测物体中的电场分布。文中使用的是有限差分法,给出了在三维空间中不同介质交界面上拉普拉斯方程的差分格式。计算结果表明当把ＥＴＵ放入ＴＥＭＣｅｌｌ的中心时,ＥＵＴ横截面上的电场分布是均匀的。     

Electromagnetic-Field Distortion Due to a Conducting Rectangular Cylinder in a Transverse Electromagnetic Cell

This paper deals with the distortion effects in a TEM cell resulting from loading by the object under test. To insure that higher order modes are ruled out as contributing factors, a brief discussion of the cutoff frequencies of these modes is presented. The paper then proceeds to a theoretical and experimental analysis of the loading effects. In the theoretical analysis for the loading effects, i.e., the electromagnetic-field distortion caused by an object under test in a TEM cell, the frequency-domain integral equation for the magnetic field, or equivalently, the current density on the surface of a perfectly conducting cylinder in a parallel-plate waveguide, is solved by the method of moments to predict the degree of magnetic-field distortion. The experimental investigations are performed by mounting a number of electrically small half loops on the surface of the conducting cylinder in a TEM cell. The loading effects in terms of magnetic-field distortion are analyzed as the ratio of one of the object dimensions (height) to the separation distance between the inner conductor and the ground plane of the TEM cell. Also, the response of an electrically small loop to both the magnetic and electric components of the electromagnetic field is used to measure the phase relation between the magnetic and electric fields, which in turn can be used to determine the degree of degradation of the TEM mode due to the presence of the conducting cylinder. These theoretical and experimental results are compared with the available quasi-electrostatic results.     

横电磁波传输室电场纵向不均匀性分析

本文导出了横电磁波传输室(TEM Cell)电场的纵向不均匀性表达式。数值结果与M.L.Crawford(1977)的实验值吻合较好。该结果可用于校正测量探头位置偏差带来的测量误差,从而提高用TEM Cell进行电磁兼容性试验和天线探头校准的测量精度。     

Theoretical modeling of longitudinal variations of electric fieldand line impedance in TEM cells

Longitudinal variations of the electric field inside a TEM cell have been observed in an in-depth experimental investigation and reported by M.L. Crawford et al. (see IEEE Trans. Instrum. Meas., vol.26, pp.225-230, Sept. 1977). Here, the authors present a theoretical approach to modeling these variations using standard transmission-line techniques, since only the dominant mode, TEM mode, is considered in this analysis. In addition, longitudinal variations of line impedance in the TEM cell are modeled. Their relations with voltage standing wave ratio (VSWR), losses, cell dimensions, and terminal load impedance are reflected in the expressions derived. Numerical results agree well with the reported experimental data at some frequencies. Concepts concerning longitudinal nonuniformity of both the field and the line impedance are proposed     

A simple method for calculating electric and magnetic fields inGTEM cell

A method based on coordinate transformation is presented to calculate the electric and magnetic field distributions in gigahertz TEM cells (GTEM cells). Here quasi-static approximations are employed, therefore the results are valid once operational frequencies well below the cutoff frequency of the cell. The method is illustrated by calculating the fields in a typical test structure. The results indicated here are useful in radiated emission and susceptibility studies     

A Method for Calculating Electric And Magnetic Fields in TEM Cells at ELF

A method is presented whereby the electric and magnetic field distributions within rectangular-strip transmission lines (TEM cells) can be calculated. Quasi-static approximations are employed, thereby restricting the validity of the results to operational frequencies well below the cell cutoff frequency. The method is illustrated by calculating the fields within an existing structure used in biological experimentation. Where possible, calculations are compared with measured data.