General solutions of Maxwell's equations for signals in a lossymedium. II. Electric and magnetic field strengths due to magneticexponential ramp function excitation

For pt.I see ibid., vol.30, no.1, p.29-36 (1988). Solutions for the electric and magnetic field strengths in a lossy medium due to a magnetic exponential ramp function excitation are presented. The solutions are in integral form and are evaluated by numerical integration methods using a digital computer. Computer plots for the electric and magnetic field strengths at different locations in the propagation medium are given. The plots obtained for the transients can be used to represent solutions in lossy media for signals that can be represented in terms of a time-series expansion of the transients     

General solutions of Maxwell's equations for signals in a lossymedium. I. Electric and magnetic field strengths due to electricexponential ramp function excitation

Modification of Maxwell's equations to obtain general solutions for a lossy medium is reviewed. It is done by adding an extra term, referred to as the fictitious magnetic charge density. The solutions, which are in integral form, are solved numerically by computer for an exponential ramp function excitation. Computer plots for the electric and magnetic field strengths as functions of time at different locations in a lossy transmission medium are presented     

Maximum electric and magnetic field strengths at a given distance from some ideal antennas

This paper is about the computation of the maximum electric and magnetic field strengths at a given distance of an antenna, close to the antenna, the maximum being taken over all orientations. We provide closed-form expressions for the maximum field strengths produced in free space by three important ideal antennas: the electric Hertzian dipole, the magnetic Hertzian dipole, and the half-wave dipole.     

Remark on Harmuth's `Correction of Maxwell's equations for signals.I' [and response]

The commenter maintains that the claims made by H.F. Harmuth in the above-titled paper (ibid., vol.EMC-28, p.250-8, Nov. 1986) that a satisfactory condition for the existence of solutions for transients in lossy media is the modification of Maxwell's equations by the addition of a magnetic current density is not valid. In his reply, Harmuth states that if the commenter's claim holds true regardless of the method of solution, he will have contributed an important simplification to the problem of transient solutions of Maxwell's equations. He provides further discussion of the commenter's point     

Simple expressions for the electric and magnetic field strengths between the elements of an infinite array

Suitable engineering expressions for the electric- and magnetic-field strengths between the elements of an infinite array are derived by employing finitely conducting earth image-theory techniques.     

Comments on `Correction of Maxwell's equations for signals I andII' [by R.J. Mohr]

The commenter states that Harmuth's (see ibid., vol.28, no.4, p.250, 1986) characterization of Godel's (1931) work is incorrect, or, at the very best, extremely misleading. He also states that Godel did not show, as Harmuth claims, that every statement cannot be proven and that they can only be disproven using counterexample     

An analytical model to predict the electric field and excitationzones due to magnetic stimulation of peripheral nerves

The main unknown factor in understanding magnetic stimulation of peripheral nerves is the distribution of the induced electric field. The authors have applied the so-called reciprocity theorem and developed an analytical model to compute the electric field and its spatial derivatives inside pseudocylindrical structures. The results can be used to predict the site of excitation in magnetic stimulation of peripheral nerves     

A technique for solution of Maxwell's equations in a moving dielectric medium

A simple technique is presented for converting a known solution for the electric and magnetic vector fields in a dielectric medium at rest into the corresponding fields in a moving dielectric medium. The technique combines methods presented by Tai [1] with a scaling procedure developed by Clemmow [2]. Tai's work reduces the moving medium problem to the solution of Maxwell's equations in a uniaxial medium, and Clemmow's procedure enables one to convert a known solution in an isotropic medium to the corresponding solution in a uniaxial medium. Thus by first solving for the fields in the medium at rest, then following Clemmow's procedure to obtain the fields in Tai's uniaxial medium, and finally applying Tai's reasoning, one may easily obtain the solution of Maxwell's equations in the moving medium.     

Electric current and electric field induced in the human body whenexposed to an incident electric field near the resonant frequency

The electric field and current density induced in the human body when this is exposed to electric fields near the resonant frequency, 53 MHz, are determined analytically. Since this frequency range includes an important amateur radio band of 50-60 MHz and exposure to electric fields at this frequency has been shown to be hazardous, the study has a specific motivation. A cylindrical model of the body is used to derive formulas for the total axial current and current density induced in the body subject to skin effect. Tabulations and graphical representations illuminate the results     

Density matrix solutions for the susceptibilities of a three-level system with arbitrary relaxation rates and field strengths

The susceptibilities for a three-level system with arbitrary pump and signal field strengths are derived for the case of arbitrary longitudinal and transverse relaxation rates.     

并矢格林函数法求解海水中电偶极子电场

海水中电偶极子的电磁场是目前水下通讯和水中目标探测方面的研究重点。利用并矢格林函数法对海水中电偶极子产生的电场进行求解,得到的解的形式简洁,且易于求解任意电流分布所产生的场。     

Two types of mesoscopic fluctuations in a high magnetic field due to bulk and boundary diffusion

The fluctuation properties of a mesoscopic sample have been studied in high magnetic fields. In the microwave photo e.m.f. vs magnetic field dependence there are mesoscopic fluctuations, their correlating magnetic field increasing with magnetic field at ω_cι ≥ 1. At still higher fields, as one approaches the quantum Hall regime, one finds mesoscopic fluctuations of two distinctly different types arising at alternating intervals of the magnetic field and corresponding to the two principal types of electron transport in the sample: the bulk diffusion and the edge current transport.     

Electric/magnetic field ratios of ground waves in a realistic terrain

An investigation of ground waves at low and medium frequencies has shown that in cluttered or undulating terrain the electric field is reduced relative to the magnetic field. This reduction applies to the median value over large areas and has different characteristics dependent on type of terrain factor (buildings, trees or undulatlons).     

Determination of the electric field in a Hall generator under influence of an alternating magnetic field

A method is described to calculate the electric field in a Hall generator under influence of an alternating magnetic field. The problem is divided into two separate problems, the first of which describes the Hall effect while the second gives the behaviour of the eddy currents. Each of these problems can be reduced to an integral equation, which is easily solved on a digital computer. The method is illustrated for a rectangular Hall generator.     

LC circuits designed for excitation of turnstile radiators consisting of three electric and three magnetic dipoles

Circuits from lumped LC elements for excitation of turnstile radiators consisting of three electric and three magnetic dipoles in the meter and decimeter wave bands are proposed. A calculation technique is developed and examples on calculation of the elements of these circuits ensuring control of the shape and spatial position of the pattern maximum are presented.     

Applications of cumulants to array processing. III. Blindbeamforming for coherent signals

For pt.II see ibid., vol.43, no.7, p.1663-7, 1995. We provide a cumulant-based blind beamforming method for recovery of statistically independent narrowband source signals in the presence of coherent (or perfectly correlated) multipath propagation. Our method is based on the fact that for a blind beamformer, the presence of coherent multipaths is equivalent to the case of independent sources with a different steering matrix. Our approach is applicable to any array configuration having unknown response. Signal sources must have nonzero fourth-order cumulants. There is no need to estimate the directions of arrival. Our method maximizes signal-to-interference plus noise ratio (SINR). A comparable result does not exist using just second-order statistics     

Comparison of asymptotic solutions for the surface field excited by a magnetic dipole on a cylinder

In the analysis of mutual coupling in apertures on a convex surface, the surface field due to a magnetic dipole on a large conducting cylinder is an important canonical problem. Over the years a number of approximate asymptotic solutions have been described in the literature. In this paper the accuracy of five of the best solutions currently available is tested by comparing them with the exact modal solution. This comparison is accomplished by placing the modal solution in a more efficient form for numerical evaluation. From a study of four ray trajectories on cylinders of radius 1.5171 and four wavelengths it is concluded that two complementing solutions due to Boersma and Lee and the author have best overall accuracy. The former solution is most accurate near the source and in the paraxial region while the Latter is best far from the source and off axis. The worst case errors observed for the test trajectories on the four wavelength cylinder were approximately 1 dB in magnitude and3degin phase for the Boersma-Lee solution and 0.5 dB and4deg, respectively, for the author's solution. Generally the errors arc considerably less than these values.     

Power enhancement in argon II narrow-tube lasers due to zeeman effect by a transverse magnetic field

The role of the Zeeman effect for the power enhancement of a small-bore argon ion laser (488.0 nm) by applying the transverse magnetic field has been investigated both experimentally and theoretically. The σ-polarized laser has a larger output power than the π-polarized laser in the wide range of magnetic field strength. Specifically, at weak magnetic fields, enhancement occurred only for the σ-polarized laser. The experimental results are interpreted in terms of the semiclassical theory of the Zeeman laser. A narrow spectrum envelope is observed in the σ-polarized laser. In the case of internal mirrors without Brewster window, it is demonstrated experimentally that π and σ polarization coexist and compete with each other.     

Model for the excitation of 1/f noise by high-frequency a.c. signals

A model is presented for the excitation of 1/f noise in carbon and semiconductor resistors by high-frequency a.c. signals. The model does not require special theories on 1/f noise; the observed 1/f noise is attributed, as usual, to resistance fluctuations.     

有限差分法在静态电磁场计算中的应用

介绍了采用有限差分法求解特殊边界条件下二维静态电场问题,并将电磁场数值方法的思想体现在处理过程中。对场域中的电势、电位进行了具体的分析和计算,给出了用C语言进行编程计算得到场量数据的流程图,最后利用MATLAB强大的绘图功能对结果进行可视化。由文章研究问题所得图形结果可以清晰的看出静电场中的电势线及电场线的分布,同时也验证了电场线与等电位线相互垂直,以及电势在媒质分界面连续的经典理论。