Measured currents and charges on thin crossed antennas in a plane-wave field

Measured distributions of current and charge per unit length on electrically long and thin crossed antennas over a ground plane are displayed for five sets of lengths that locate the junction at minima and maxima of charge and include resonant and antiresonant combinations of lengths. The currents are induced by a normally incident plane electromagnetic wave with its electric vector parallel to one of the mutually perpendicular antennas. Attention is given to the behavior of currents and charges near the junction where Kirchhoff's current law and equality of charges per unit length are observed. For purposes of physical understanding a zero-order explanation of the distributions of charge per unit length and current is given in terms of resonant and forced components.     

Induced Currents and Charges on Thin Cylinders in a Time-Varying Electromagnetic

The distributions of current and charge induced on the surface of electrically thin metal cylinders by an external electromagnetic field are described by means of theoretically and experimentally determined graphs. Various possible standing-wave patterns are shown including some with unexpected properties such as the coincidence of current and charge minima. A knowledge of these distributions is essential to the determination of the shielding properties of imperfectly conducting cylinders and cylinders with small aperttires. It is also a prerequisite o an understanding of currents and charges on crossed metal cylinders including aircraft exposed to an electromagnetic pulse. The significance of the location of the junction in the standing-wave patterns is pointed out.     

Current induced on single and crossed electrically short and thin tubular cylinders by a normally incident plane electromagnetic wave

The currents induced in electrically thin conducting tubes are evaluated from the general solution of the coupled integral equations derived by C. C. Kao [5] in the form of transverse Fourier components. It is shown that on a single cylinder of length2hand radiusain a normally incidentE-polarized field with wavenumberk, the rotationally symmetric zero-order term dominates forka leq 0.1and increases in magnitude askais reduced, but only whenkh > 1. Under these conditions, supplemented with the inequalitya ll h, thin-cylinder theory is valid. The relatively small first-order term produces small departures from rotational symmetry that increase or decrease the current on the illuminated side depending on the condition of axial resonance and the location of the cross section in the standing-wave pattern. Askhis reduced so thatka < kh ll 1, the rotationaily symmetric part of the axial current decreases and becomes negligible compared to the first-order current which is proportional tocos theta. Thin-cylinder theory is then no longer useful. When two electrically thin tubes intersect, thin-wire theory and junction conditions determine only the rotationally symmetric part of the axial currents in the arms. These dominate only when the arms of the cross are not electrically short. The fast-order nonrotationally symmetric components of the axial current and the transverse currents can be determined from the incident magnetic field. They dominate when the arms of the cross are electrically short. The significance of the surface currents and charges on aircraft illuminated by an electromagnetic wave or pulse at low frequencies is pointed out.     

Diakoptic theory for multielement antennas

A theory is presented for the analysis of multielement antennas which consist of interconnected, conductive structure elements of electrically small dimensions. The theory is based on the retarded electromagnetic potentials which permit a diakoptic approach to the problem. The antenna is broken up into its individual structure elements. Each element is assumed to be excited by currents which are impressed at its terminals, i.e., junctions with adjacent elements (current coupling) and by the electric fields of the currents and charges on all the other elements (fieid coupling). Both excitations are treated independently. Each impressed current produces a "dominant" current distribution, a characteristic of the element, which can be readily computed. Current coupling is formulated by "intrinsic" impedance matrices which relate the scaler potentials at the terminals of an element, caused by its dominant current distributions, to the impressed currents of the element. Field coupling produces "scatter" currents on all the elements and is formulated by a "fieid-coupling" matrix which relates the scalar potentials at the terminals, caused by field coupling, to the impressed currents at all the terminals. Intrinsic and "field-coupling" matrices are combined to form the "complete" impedance matrix of the diakopted antenna. Enforcing continuity of the currents and equality of the scalar potentials at all the interconnections between the elements yields a system of linear equations for the junction currents and the input impedance of the antenna. Current coupling dominates field coupling. Fieid coupling is primarily affected by the dominant current distributions of the elements, and in general the scatter currents have negligible effect on it. Although detailed numerical investigations will be presented in another paper, a simple example is included here to demonstrate that the diakoptic theory yields very good results even if greatly simplified assumptions are made.     

The effect of material stresses on electromagnetic boundary conditions

The appearance of a layer of charge or current on the boundary of a material usually implies that a discontinuity in an electromagnetic field occurs at that boundary. The converse is not necessarily true. The reaction of the electromagnetic field to the charge or current layer is a stress communicated across the boundary. Determination of the charge or current on a boundary must take all the stresses and electromechanical interactions at the boundary into account. Calculating surface currents or charges derived from electromagnetic field quantities alone, ignoring mechanical stresses, may lead to wrong answers at material boundaries. In short, the occurrence of charge or current on material in the presence of an electromagnetic field is intimately related to momentum conservation. A postulate equivalent to identifying the Poynting vector with energy flow is introduced, linking surface currents and charges to momentum balance at the surface. A formally correct method for calculating surface currents and charges based on momentum balance is described.     

Efficient method of moments formulation for large PEC scatteringproblems using asymptotic phasefront extraction (APE)

A method is introduced for reducing the exorbitant dependence on computer storage and solution time in the method of moments (MoM) for electrically large electromagnetic (EM) scattering problems. The unknown surface currents on large, smooth parts of a perfect electrical conductor (PEC) scatterer are expressed by an efficient set of linearly phased surface current basis functions. The phasefront characteristics of the surface currents are numerically extracted from known current samples obtained from a lower-frequency solution of the same configuration. The use of such basis functions for efficiently representing the surface currents that are constructed in terms of linearly phased currents at higher frequencies is justified by considering the form of the surface currents predicted by high-frequency asymptotic ray methods. The procedure for extracting the current phasefronts is purely numerical, obviating computationally expensive and nonrobust operations such as ray-tracing, and thus, is amenable to general purpose scattering codes. The new MoM with linearly phased basis functions is shown to greatly relieve the storage and solution time of the conventional MoM while accurately reproducing the induced surface currents and scattered fields of some chosen targets     

A boundary-element solution of the Leontovitch problem

A boundary-element method is introduced for solving electromagnetic scattering problems in the frequency domain relative to an impedance boundary condition (IBC) on an obstacle of arbitrary shape. The formulation is based on the field approach; namely, it is obtained by enforcing the total electromagnetic field, expressed by means of the incident field and the equivalent electric and magnetic currents and charges on the scatterer surface, to satisfy the boundary condition. As a result, this formulation is well-posed at any frequency for an absorbing scatterer. Both of the equivalent currents are discretized by a boundary-element method over a triangular mesh of the surface scatterer. The magnetic currents are then eliminated at the element level during the assembly process. The final linear system to be solved keeps all of the desirable properties provided by the application of this method to the usual perfectly conducting scatterer; that is, its unknowns are the fluxes of the electric currents across the edges of the mesh and its coefficient matrix is symmetric     

放射状双pn结抑制片上电感衬底损耗

使用标准CMOS工艺,在放射状的n阱上面扩散p＋,使垂直和水平方向形成双pn结,将此结放在电感的底部用来抑制衬底损耗．提出并实验证明了该结构形成的高阻区厚度不是垂直pn结耗尽层的厚度,而是最低层的pn结的深度．首次通过接地的p＋扩散层屏蔽电感到衬底电场,水平和垂直pn结耗尽层厚度随着pn结反向偏压升高改变衬底有效的高阻区厚度,电感品质因数跟随高阻区厚度升降,有效地证明了pn结衬底隔离可以降低电感的衬底电流造成的损耗．     

放射状双pn结抑制片上电感衬底损耗

使用标准CMOS工艺,在放射状的n阱上面扩散p+,使垂直和水平方向形成双pn结,将此结放在电感的底部用来抑制衬底损耗.提出并实验证明了该结构形成的高阻区厚度不是垂直pn结耗尽层的厚度,而是最低层的pn结的深度.首次通过接地的p+扩散层屏蔽电感到衬底电场,水平和垂直pn结耗尽层厚度随着pn结反向偏压升高改变衬底有效的高阻区厚度,电感品质因数跟随高阻区厚度升降,有效地证明了pn结衬底隔离可以降低电感的衬底电流造成的损耗.     

A review of analytically determined electric fields and currents induced in the human body when exposed to 50-60-Hz electromagnetic fields

In this review paper, analytical methods are used to determine the electric field and current induced in the conducting human body when this is exposed to an electromagnetic field at extremely low frequencies (ELFs) or very low frequencies (VLFs). This is done by treating it as a parasitic antenna when this is modeled successively as a sphere, an ellipsoid, and a cylinder. Because the body is electrically very short at ELF and VLF, the axial current depends primarily on the length of the body. Comparison with the ellipsoidal shape shows that the induced current is virtually independent of the cross-sectional shape. It is concluded that the axial current induced in the cylinder is a good approximation of the current induced in an actual body with the same length and mean cross sectional area. References to persons standing on the earth and with the arms raised are given. The significance of the accurate knowledge of induced currents and fields for biomedical purposes is discussed.     

A Three-Dimensional Finite-Difference Solution of the External Response of an Aircraft to a Complex Transient EM Environment: Part II-Comparison of Predictions and Measurements

Experimental charge and current measurements have recently been performed on an aircraft when it was exposed to the transient electromagnetic field of an electromagnetic-pulse (EMP) simulator. These new data allow a test of the predictive capabilities of the three-dimensional finite-difference method for realistic aircraft aircraftsimulator-test problems. Comparisons made between measurements and predictions show that the three-dimensional finite-difference technique provides reasonably accurate predictions for the induced currents and charges on a complex object responding to an applied transient electromagnetic field in the presence of a lossy earth.     

System-generated EMP

The state of the art of system-generated electromagnetic pulse (SGEMP) is reviewed with particular emphasis on the empirical laws of photoelectron emission current and the analytical and numerical techniques employed for the calculation of currents and charges induced on the surface of a system such as a satellite.     

Excess currents induced by hot hole injection and FN electroninjection in thin SiO2 films

The behavior of excess currents induced by Fowler-Nordheim electron injection stress (FN electron injection) has been investigated for 6.0-nm oxides. Excess currents are induced by FN electron injection in 6.0-nm oxides together with positive charges being induced in it. To clarify the role of hole injection in FN electron injection, the behavior of excess currents induced by substrate hot hole injection has also been investigated in 6.0-nm oxides. The leakage behavior after hot hole injection is the same as FN electron injection. The excess currents induced both by the FN electron injection and by the substrate hot hole injection are due to trap-assisted tunneling and field enhancement at the cathode due to the positive trapped charge. The charge centroid of the positive charges induced by both stresses are located 3.0 nm from the Si/SiO₂ interface which is at the center of 6.0-nm oxide. The excess currents induced by hot hole injection and FN electron injection are caused by traps in SiO₂ films produced by injected holes from the anode     

EMF Induced in a p–n Junction under a Strong Microwave Field and Light

Semiconductors - The effect of a strong electromagnetic field on currents and electromotive forces in a p–n junction is considered. It is shown that a p–n junction upon exposure to an...     

基于CBFM的微带天线阵列电磁特性分析

针对传统矩量法分析电大目标难度大的问题,近几年提出一种有效的方法——特征基函数法。文中采用此方法结合空域格林函数法对一些微带天线阵列的电磁特性进行了研究,其中研究并运用磁流圆盘来模拟同轴激励源,运用简化附加模模型模拟线面连接处的电流。数值分析结果与MOM、软件仿真、相关文献的结果吻合良好,与MOM相比计算时间大大减少,从而证明了此方法的正确性、通用性和优越性。     

The tapered antenna and its application to the junction problem for thin wires

When electrically thin conductors of different cross sectional size meet, the continuity of current is assured by Kirchhoff's current law. Additional conditions must be imposed on the derivatives of the currents or the charges per unit length. The nature of the required conditions is determined from an analysis of the tapered antenna.     

Study of two types of turnstile aerial immersed in a warm plasma †

The radiation properties of two types of turnstile aerial in a warm plasma are studied. One aerial type has crossed dipoles fed with currents in quadrature ; the other has currents in the four elements, such that the current in any one element is ±π/2 out of phase with the current in adjacent elements. The field patterns of both the electromagnetic and plasma waves are investigated, and it is shown that the field strength of the electromagnetic waves is reduced by the presence of the plasma. The radiation resistances of the electromagnetic and plasma waves of the two aerial types are evaluated for specific aerial parameters.     

Estimation of High-Frequency Currents From Near-Field Scan Measurements

High-frequency currents on the pins of integrated circuits (ICs) and on printed circuit board (PCB) traces are needed to predict and analyze electromagnetic interference in high-speed devices. These currents can, however, be difficult to measure when traces are buried within the PCB or chip-package, especially when several current-carrying traces are in close proximity. Techniques for estimating high-frequency currents from near-field scan data are proposed in this paper. These techniques are applied to find currents on the pins of an IC, on traces buried beneath other traces in a PCB, and on traces over a slot in the ground plane. Methods of dealing with the ill-posed nature of the current-estimation problem are discussed, as are applications to electrically large structures. A study of the sensitivity of the technique to errors in the measured fields, errors in the circuit geometry, and errors in the estimated dielectric constant of the PCB or chip package show that, for reasonable errors in these parameters, currents can be estimated to within an average of 20% (1.6 dB) or less of their correct values.     

Finite-element approximation of electromagnetic diffraction by arbitrarily shaped surfaces

A general finite-element method is applied to compute the skin current of a perfectly conducting surface illuminated by an incident electromagnetic wave. Surface charges over any element and currents flowing through any edge are approximated by polynomials of degree m. Some radiation patterns of two horns are calculated and compared with those obtained from experiment.     

Modeling of the electrodynamic contact of two materials under the action of electromagnetic waves

A mathematical model of bilateral boundary conditions coupling monochromatic electromagnetic fields on both sides of the transition layer between two materials is developed. The field-induced double-layer surface charges and currents and complex surface capacitances and inductances of the transition region are taken into account. An analytic solution to the boundary value problem of penetration of an arbitrarily polarized plane electromagnetic wave through a two-layered screen with a transition plane region between the layers is obtained. The transmission and reflection coefficients for a plane wave are calculated.