ESD field penetration through slots into shielded enclosures: atime domain approach

This paper presents a time domain approach for the analysis of the coupling between an electrostatic discharge (ESD) current and the internal region of a shielded enclosure with a slot. The application of the equivalence principle allows us to obtain an integro-differential equation for the unknown distribution of the aperture electric field. The numerical solution is obtained by an iterative procedure developed by the method of moments (MoM) in the time domain. The approach is also applied at the case of a transient incident field of a plane wave impinging on the enclosure. The use of proper impulse responses for the space and cavity regions make the model efficient from a computational point of view, without loss in accuracy. Theoretical results are validated by measurements     

ESD辐射场测试研究

测试一直是静电与电磁防护研究的瓶颈.针对ESD辐射场测试问题,提出了能量有效带宽和动态范围有效带宽的概念,并根据IEC61000-4-2标准规定的ESD电流波形,采用数值方法估算了ESD辐射场的带宽以及上升时间对带宽的影响.在此基础上成功研制了带宽为3.5Hz~1GHz(±1.5dB),动态范围60dB,测试灵敏度可调的ESD辐射场测试系统,并实际测试了IEC61000-4-2标准规定的水平和垂直耦合电场.     

Field penetration into metallic enclosures through slots excited byESD

The coupling through apertures between an electrostatic discharge (ESD) current flowing on the external shield of a metallic enclosure and the electromagnetic field of its internal region is analyzed; the excitation of the electric field on the apertures by the ESD and then the evaluation of the internal field are calculated separately, by means of the finite difference time domain (FDTD) technique and the modal expansion, respectively. All the numerical results obtained with this simple and numerically efficient approach have been validated by measurements     

Transient response of the infinite cylindrical antenna and scatterer

The transient response of an infinite cylindrical antenna and scatterer is obtained by time gating a time-dependent electric-field integral equation for thin wires of finite-length. The driving point current and broadside radiated field approximate the driving point voltage in the antenna case, while the current excited in the scattering case approximates the time integral of the incident field. This approximate integral relation is used to estimate currents excited on cylindrical structures without employing the complete integral equation solution procedure.     

Optimal Radiated Waveforms From an Arbitrary UWB Antenna

Solutions are presented for the optimal electric field waveforms radiated by an arbitrary ultrawideband (UWB) antenna. Optimization criteria include maximization of the electric field amplitude at a particular time and location, or maximization of energy density over a specified time interval at a particular location. Assuming bandpass signals, constraints are placed on the total radiated energy, the Q of the antenna, and the size of the antenna. The solution is developed using a spherical mode expansion of the fields radiated by an arbitrary antenna enclosed by a spherical mathematical surface, and optimized using variational methods. A closed-form result is obtained for the case of amplitude maximization, while an integral equation must be solved numerically for the case of energy maximization in a time interval. An interesting result from these solutions is that the shapes of the optimal radiated field waveforms are largely independent of the size of the antenna. The solutions also indicate that the antenna characteristics that provide optimum field amplitude or energy in the transient case are identical to those associated with maximum gain in the CW case.     

电磁场积分方程时间步进解法稳定性的研究

本文对用三角片状单元剖分及做相应的矢量基函数展开,采用空间域的Galerkin矩量法,时间域采用步进递推方法解电磁场时空积分方程并进行了程序实现.研究了这种方法的优缺点,分析了计算中出现的振荡发散现象,与细线栅网结构剖分方法进行了比较,从中得到关于时空积分方程时间步进解法稳定性的一些结论.     

Transient emission from microstrip interconnects: theoreticalformulation and CAD modeling

A hybrid technique suitable for the space-time analysis of the transient spurious emission from microstrip interconnects is presented. The proposed technique requires the preliminary evaluation of the surface current excited on the microstrip interconnecting lines by means of a transmission line model accounting for dispersive effects. The radiated field is then computed in the frequency domain by applying the saddle-point asymptotic technique to the integral expression of the electric field involving the dyadic Green's function. The transient signals excited along the interconnects, and the corresponding radiated field, are finally determined by using the IFFT. Radiation mechanisms are investigated, and the influence of the structure's electrical and geometrical parameters is discussed     

Numerical simulation of electromagnetic fields radiated by lightning return stroke channels: a wavelet-based approach

The antenna theory model is widely employed to numerically simulate the propagation of current wave along lightning return stroke channels and compute the radiated electromagnetic fields. In this model, the channel is approximated as a vertically straight or a horizontally bent thin-wire antenna above perfectly conducting ground for which the numerical solution of the governing electric field integral equation in frequency domain by the conventional method of moment is prohibitively slow. This paper proposes an efficient algorithm to substantially reduce the computation time of the numerical process for the entire frequency components of the excitation current. In this algorithm, a class of predefined wavelet packet transform is first used to effectively sparsify the resulting moment matrix equations. A proper iterative solver is then utilized to take the full advantages of manipulatory sparse matrices. To accelerate the construction of the original moment matrix, the reciprocal closed-form mutual impedance of sinusoidal electric dipoles and the symmetry of the model are fully exploited. A good agreement is observed with computed data found in technical literature while the overall computational time is reduced remarkably.     

Induced current in and scattered field from a finite cylinder with arbitrary conductivity and permittivity

A finite cylinder with arbitrary conductivity and permittivity is illuminated by an EM wave. The induced current in and the scattered field by the cylinder are determined based on the numerical solution of a tensor integral equation. An experiment has been conducted to verify the theory. Biological and metallic cylinders are emphasized in the study.     

Numerical Prediction and Measurement of ESD Radiated Fields by Free-Space Field Sensors

This paper describes the evaluation of electric and magnetic fields due to electrostatic discharges (ESDs) using an efficient numerical prediction model and measurements obtained with simple field sensors. The numerical prediction model is implemented using software based on the finite integration technique (FIT). The ESD generator is efficiently modeled, and the contact-mode discharge current is well reproduced taking into account the loading effect of the generator. Simple free-space field sensors are effectively used to measure the fields from an ESD event. Suitable numerical and theoretical characterizations of these sensors are proposed to derive a sensor transfer function that permits the fields to be reconstructed from the measured voltage. The numerical characterization is performed by Microwave Studio (MWS), while the theoretical characterization is based on lumped element circuit models of the sensors. The validation of both the proposed procedures indicates good accuracy up to 2 GHz as required by the International Electrotechnical Commission standard for ESD measurements.     

Exact solutions of electromagnetic fields in both near and farzones radiated by thin circular-loop antennas: a general representation

This paper presents an alternative vector analysis of the electromagnetic (EM) fields radiated from thin circular-loop antennas of arbitrary radius a. This method, which employs the dyadic Green's function in the derivation of the EM radiated fields, makes the analysis more general, compact, and straightforward than those two methods published recently by Werner (1996) and Overfelt (1996). Both near and far zones are considered so that the EM radiated fields are expressed in terms of the vector-wave eigenfunctions. Not only the exact solution of the EM fields in the near and far zones outside the region (where r>a) is derived by the use of the spherical Hankel function of the first kind, but also the closed-series form of the EM fields radiated in the near zone inside the region 0⩽r   

加载介质覆盖层的圆柱共形微带天线的全波分析

基于严格的全波方法分析计算了介质薄层覆盖下由探针激励的圆柱共形微带天线的输入阻抗和辐射方向图.首次详细地推导出了此结构下适于数值计算的微带帖片上的表面电流形式,并通过矩量法求解电场积分方程得到感应电流的分布.最终,通过数值结果揭示出了覆盖介质层对天线特性的影响并且与已发表文献及其他数值方法的结果进行对比,证明了方法的正确性.     

Numerical Solution of Coupling Between Two Collinear Parallel-Plate Waveguides

The problem of coupling between two collinear parallel-plate waveguides is investigated numerically using moment methods. The exciting mode in the waveguide is assumed as the incident field, and the integral equation for the induced current is expressed in terms of the reflected, transmitted, and evanescent currents on the waveguides. The integral equation is then solved numerically by a point-matching method and the reflection and the transmission coefficients and the radiated fields are obtained. To examine the accuracy of the results, the special case of a semi-infinite exciting waveguide coupled to a finite coupled waveguide is also considered and is solved numerically by treating the singularities of the induced currents using a transformation method. For a TE/sub 0,1/ excitation of the exciting waveguide, the results of both numerical methods are compared with the analytical results obtained previously using the Wiener-Hopf technique, and are found to be in good agreement. The methods are then used to study the effect of the coupled waveguide on the radiation field.     

Computer simulation of ESD from voluminous objects compared totransient fields of humans

Computer simulation of electrostatic discharge (ESD) for simplified objects is described and compared to measured transient fields of human/metal ESD. The simulation algorithm uses the method of moments in time domain, coupled with nonlinear arc resistance model. Transient currents and fields are analyzed from the electromagnetic compatibility (EMC) point of view. Validation of the numerical simulation is done by comparison to experimental data. The simulated structure models the human/metal ESD in its peak current and field values and their derivatives reasonably well     

Analysis of lightning-radiated electromagnetic fields in the vicinity of lossy ground

An antenna theory (AT) approach in the frequency domain is presented to compute electromagnetic fields radiated by a lightning return stroke. The lightning channel is modeled as a lossy-wire monopole antenna (a wire antenna with distributed resistance) energized by a current source at its base, and the ground is modeled as a lossy half-space. The method of moments is used for solving the governing electric field integral equation (EFIE) in the frequency domain. The resultant current distribution along the channel is used to calculate electromagnetic fields at different distances from the channel. All field components are evaluated using a rapid but accurate procedure based on a new approximation of Sommerfeld integrals. In contrast with the previous models, the approach proposed here is characterized by a self-consistent treatment of different field components in air or on the surface of a lossy half-space. It is shown that the omission of surface wave terms in the general field equations, as done in the perfect-ground approximation, can strongly affect model-predicted field components.     

导体目标瞬态电磁散射的时空矩量法研究

时域积分方程的矩量法是求解瞬态电磁散射的方法之一。研究了基于加权Lagurre函数和RWG基函数分别作为时间、空间基函数的时空矩量法,给出了时域磁场积分方程时空矩量法的全部计算公式,编制了相应串行和并行计算程序。计算结果表明：该方法具有很好的时域稳定特性,为宽带电磁散射分析提供了可能,同时也指出了其应用的局限性,为改进其方法提供了参考。     

A stable solution of time domain electric field Integral equation for thin-wire antennas using the Laguerre polynomials

In this paper, a numerical method to obtain an unconditionally stable solution of the time domain electric field integral equation for arbitrary conducting thin wires is presented. The time-domain electric field integral equation (TD-EFIE) technique has been employed to analyze electromagnetic scattering and radiation problems from thin wire structures. However, the most popular method to solve the TD-EFIE is typically the marching-on in time (MOT) method, which sometimes may suffer from its late-time instability. Instead, we solve the time-domain integral equation by expressing the transient behaviors in terms of weighted Laguerre polynomials. By using these orthonormal basis functions for the temporal variation, the time derivatives can be handled analytically and stable results can be obtained even for late-time. Furthermore, the excitation source in most scattering and radiation analysis of electromagnetic systems is typically done using a Gaussian shaped pulse. In this paper, both a Gaussian pulse and other waveshapes like a rectangular pulse or a ramp like function have been used as excitations for the scattering and radiation of thin-wire antennas with and without junctions. The time-domain results are compared with the inverse discrete Fourier transform (IDFT) of a frequency domain analysis.     

Ultrawide-band modeling of transient radiation from aperture antennas

A new method for the numerical calculation of transient field radiated through aperture-type antennas (slot, open-ended waveguide, and horn) is described. The finite-difference time-domain method is applied for the near-field prediction in the close surrounding of the antenna and a proper data-fitting procedure of the aperture field, involving interpolating functions with separation of space- and time dependence, permits: 1) to calculate "off-line" the radiated field without the need to store a great amount of data; 2) to avoid, in the case of far field, the numerical evaluation of radiation integral; and 3) to obtain approximate far field formulas which are still separable with regard to space and time. The method enables a full data reusability in calculation of field pattern over a wide angular range at a same time, or of the transient response at fixed observation points.     

渐近波形估计技术用于介质柱宽角度RCS的计算

基于渐近波开估计（AWE）技术和矩量法（MOM）快速预测任意形状非均匀介质柱体的单站雷达散射截面RCS方向图,采用矩量法求解介质柱的电场积分方程,得到介质柱在某一给定方向入射波照射下的极化电流,然后利用AWE技术将任一角度入射波照射下的极化给定角度附近展开成Taylor级数,通过Pade逼近将Taylor级数转化为有理函数,由此可获得介质柱在任一角度入射波照射下的极化电流,进而计算出RCS方向图。计算结果表明AWE完全能逼近MOM精确计算的曲线,同时可加快计算速度。     

EM fields associated with lightning channels: on the effect oftortuosity and branching

Usually the electric and magnetic fields associated with lightning have been computed by assuming the lightning current to be contained in a straight vertical channel of negligible cross section above a flat perfectly conducting plane. Such a model, which does not take into account that real lightning is characterized by tortuosity and branching, is not able to justify the fine structure of the fields radiated by lightning discharges whose time-domain behavior exhibits a jagged shape with remarkable spectral content in several bands of practical interest. In this work the effect of channel tortuosity and branching is investigated by adopting a suitable numerical technique. The discharge channel has been regarded as a fractal antenna whose associated EM field has been evaluated by superimposing the contribution of the single line radiators composing the whole channel. Such a field has been compared with that generated by a simple dipole antenna in order to study the influence of the fractal nature of the channel on the generated EM fields. The relationship between the fractal dimension of the discharge channel and the fractal dimension of the generated time domain EM fields has been considered and the influence played on such a relationship by the distance between EM source and observation point has also been studied by analyzing the fields evaluated at far and close distances