Localizing the spatial and temporal electromagnetic fields on theaxis of a lossy cylinder

Given a specified form, both in time and space, for the electromagnetic fields on the axis of a lossy cylinder, the authors determine, analytically, the required azimuthally symmetric source distribution on the surface of the cylinder that generates such internal fields. They then show that this source is equivalent to an array with finite number of cylindrical slots in a metal encasing that are impulsed by specified voltages at a finite sequence of discrete times. A confirming forward calculation exhibits excellent agreement between the specified field form and that generated by the array of cylindrical slots. Potential applications are to hyperthermic cancer therapy, bioelectromagnetics and nondestructive testing     

Preforming an electromagnetic pulse in lossy medium

Plane wave propagation of a transient signal in a lossy homogeneous medium is considered. It is shown that it is possible to prescribe a source signal waveform which will produce a Gaussian signal waveform after propagating a specified distance.<>     

Subsurface electromagnetic fields of a circular loop of current located above ground

The electromagnetic fields produced by a circular loop of current is considered for a homogeneous half-space model of the earth. The integral representations for the subsurface field are evaluated numerically and presented in graphical form.     

Enhanced electromagnetic power deposition in a lossy medium

It is demonstrated that an aperture antenna, excited by a leaky wave, will transfer power into an homogeneous lossy half-space at levels exceeding expectation. However, such local enhancements are only possible in the near-field region in the central part of the array. With the proper choice of parameters, enhancements of the order of 15 dB can be achieved. The calculated results are relevant to hyperthermic heating in cancer therapy and to related problems in biological hazards     

Numerical solution of fields in lossy structures using MAGY

Lossy structures are used in vacuum electronic devices to control and suppress modes. Numerical simulation of the effect of these lossy structures is critical to the design and optimization of devices. The gyrotron simulation code MAGY makes use of the generalized telegraphist's equations in which the transverse structure of fields is represented as a sum of local modes of a metallic waveguide. If the wall is not a perfect conductor then sum over modes is not uniformly convergent. We have developed an algorithm to deal with this problem and allow for the simulation of structure with highly lossy walls. The theory and implementation of this algorithm are presented     

Contribution of resonance to ground bounce in lossy thin filmplanes

This paper discusses the pulse propagation effects on lossy thin film planes. The ground bounce phenomena produced by the resonance on planes has been captured using a combination of modeling techniques and measurements. Macromodeling method has been used to explain the transient phenomena on planes by using the dominant poles and residues of the system     

有损土壤上的多导体传输线的时域分析

将多导体传输线（ＭＴＬ）的土壤复数阻抗拓展为土壤运算阻抗,采用Ｐａｄｅ展开法,提出了计及土壤影响的多导体传输线的时域模型,建立了该模型的时域有限差分（ＦＤＴＤ）算法。通过对计及土壤影响的架空单导体和双导体传输线的波过程计算,表明本文方法的正确性,并可以应用于超高压变电站高压母线和超高压输电线路的瞬态电磁干扰计算。     

FDTDSIBC混合方法计算近地导线表面电流

通过在FDTD方法中引进时域表面阻抗界条件来研究瞬态电磁脉冲对有耗地面附近电缆线耦合问题。由频域表面阻抗出发通过拉氏变换得到时域表面阻抗边界条件（SIBC）,并将这种边界条件应用于FDTD方法中来模拟有耗地面的反射。计算结果表明了些方法的有效性。     

Rigorous analysis of radiation properties of lossy patch resonatorson complex anisotropic media and lossy ground metallization

An extended spectral-domain immittance approach for the rigorous analysis of resonant frequencies and radiation characteristics of microstrip resonators is presented. The dyadic Green's function in the spectral domain is modified to include a complex anisotropic substrate with both permeability and permittivity tensors, lossy ground metallization, and a lossy conducting patch of conventional or superconducting material. Closed-form expressions for the transverse propagation constants and related immittances of TE and TM waves in the spectral domain lead to a CPU-time efficient algorithm that is operational on standard workstations. Numerical results show how the radiation characteristics are affected by losses as well as uniaxial and biaxial anisotropies     

Riemann-Green function solution of transient electromagnetic plane waves in lossy media

B. Riemann's (1953) solution of the Cauchy problem for the linear wave equation is used to find a closed-form solution for the problem of transient nonsinusoidal waves is lossy media. A method for finding the required Riemann-Green function is discussed. The evolution of a wavefront propagating in a semi-infinite lossy medium is studied, and a series solution for the corresponding electric field is obtained.<>     

Robust finite-element solution of lossy and unbounded electromagnetic eigenvalue problems

An efficient algorithm is presented for the finite-element solution of electromagnetic eigenvalue problems associated with lossy and unbounded structures. The algorithm is based on the E/spl I.oarr/ - B/spl I.oarr/ formulation of the finite-element approximation of the electromagnetic equations. The special relationship between the vector bases used for the expansion of the electric field vector E/spl I.oarr/ and the magnetic flux density vector B/spl I.oarr/ is used to reduce the computational complexity of the proposed formulation. The occurrence of spurious DC modes is avoided through the careful selection of divergence-free initial vectors in the Lanczos-Arnoldi-based iterative schemes used by the proposed algorithm. The resultant algorithm is only marginally more expensive than standard finite-element-based algorithms used for electromagnetic eigenvalue problems involving lossless structures. Numerical experiments from the application of the proposed algorithm to the eigenvalue analysis of both lossless and lossy cavities are used to demonstrate its accuracy, computational efficiency, and robustness.     

Characterisation of electromagnetic fields in buildings

Cumulative distributions of both electric and magnetic fields are given for the indoor environment in Canada. The statistics indicate that an E-field strength susceptibility limit of 3 V/m corresponding to a cumulative probability level of 95.0%, and a susceptibility limit of 5 V/m, with a cumulative probability level of 99.2%, would be adequate for the territory covered. A gamma distribution model of the data is found to be superior to a Gaussian model.<>     

Influence of a lossy ground on lightning-induced voltages onoverhead lines

A comprehensive study on the effect of a lossy ground on the induced voltages on overhead power lines by a nearby lightning strike is presented. The ground conductivity plays a role in both the evaluation of the lightning radiated fields and of the line parameters. To be calculated by means of a rigorous theory, both fields and line constants need important computation time, which, for the problem of interest, is still prohibitive. The aim of this paper is to discuss and analyze the various simplified approaches and techniques that have been proposed for the calculation of the fields and the line constants when the ground cannot be assumed as a perfectly conducting plane. Regarding the radiated electromagnetic field, it is shown that the horizontal electric field, the component which is most affected by the ground finite conductivity, can be calculated in an accurate way using the Cooray-Rubinstein simplified formula. The presence of an imperfectly conducting ground is included in the coupling equations by means of two additional terms: the longitudinal ground impedance and the transverse ground admittance, which are both frequency-dependent. The latter can generally be neglected for typical overhead lines, due to its small contribution to the overall transverse admittance of the line. Regarding the ground impedance, a comparison between several simplified expressions used in the literature is presented and the validity limits of these expressions are established. It is also shown that for typical overhead lines the wire impedance can be neglected as regard to the ground impedance     

Pattern matching and lossy data compression on random fields

We consider the problem of lossy data compression for data arranged on two-dimensional arrays (such as images), or more generally on higher dimensional arrays (such as video sequences). Several of the most commonly used algorithms are based on pattern matching: Given a distortion level D and a block of data to be compressed, the encoder first finds a D-close match of this block into some database, and then describes the data by describing the position of the match. We consider two idealized versions of this scenario. In the first, the database is taken to be a collection of independent realizations of the same size and from the same distribution as the original data. In the second, the database is assumed to be a single long realization from the same source as the data. We show that the compression rate achieved (in either version) is no worse than R(D/2) bits per symbol, where R(D) is the rate-distortion function. This is proved under the assumptions that (1) the data is generated by a Gibbs distribution, and (2) the distortion measure is a metric, generalizing the corresponding one-dimensional bound of Steinberg and Gutman (1993). Using large deviations results by Dembo and Kontoyiannis (see ibid., vol.48, p.1590-15, 2000) and by Chi (2001), we are able to give short proofs for the present results.     

Unrelated illumination method for electromagnetic inversescattering of inhomogeneous lossy dielectric bodies

A method aimed at reconstructing the complex permittivities of inhomogeneous lossy dielectric bodies is proposed. The method is based on the principle that sufficient information about a dielectric body can be obtained from the scattered field when the body is illuminated by an incident field composed of unrelated components. The derivations of the formulas are presented, and some numerical examples are given. The accuracy of the results show that the method has great potential in electromagnetic inverse scattering and microwave imaging     

Guided quasistatic fields in electromagnetic measurement-while-drilling

The quasistatic fields of extremely low frequencies (ELF) employed to communicate from underground to the ground surface in the electromagnetic measurement-while-drilling (EM-MWD) system are investigated. Three types of well, the vertical well, directional well, and horizontal well are considered. Computed results are obtained for various parameters, including the operating frequencies and the Earth's conductivities. It is demonstrated that long drill strings have a guiding effect which is advantageous to the data transmission.<>     

Experimental study of lightning-induced voltage on an overhead wireover lossy ground

Experiments on the lightning-induced voltage on an overhead wire with a simulated lightning channel and a 1/20 reduced-scale model have been carried out on a lossy ground. This method is quite useful in testing various coupling models as repeated measurement along with a simple simulated lightning channel is possible. The electrical characteristics of the ground, indispensable in the calculation of the induced voltage over lossy ground, are evaluated through the comparison of the measured and the calculated horizontal electric field waveforms. The coupling model adopted in the numerical calculation of the induced voltage, including the terminations of a finite line, is verified by the good agreement of the measured and the calculated voltage waveforms. This result also verifies the usefulness of the measurement of the horizontal electric field waveform in assessing the ground conductivity in the frequency range of interest     

核电磁脉冲地波传播规律

介绍了核电磁脉冲地波传播的理论计算方法,研究了当大地电导率大于0.005 S/m时,地波传播函数随频率及传播距离的变化规律,并计算了不同传播距离核爆电磁脉冲的地波电场。结果表明,频率越高,传播距离越远,传播函数的幅值越小;核爆电磁脉冲的传播距离为500 km时,电场的幅度会有大于一个量级的衰减。