Showing papers in "IEEE Transactions on Electromagnetic Compatibility in 1988"
TL;DR: In this paper, the basic expressions of a plane-wave shielding theory are modified and plotted with universal parameters for convenient use in performance calculations of both solid and perforated sheets.
Abstract: Plane-wave shielding theory is developed and discussed for a number of important cases such as single, double, and laminated shields. For application to design, the basic expressions are modified and plotted with universal parameters for convenient use in performance calculations of both solid and perforated sheets. Performances of solid copper and iron shields have been calculated and are presented in both tabular and graphical form. For these and other materials, measurement results of various experiments are tabulated for a number of different material forms and for various incident-wave impedances. Some consideration is given to shielding discontinuities and trends in modern shielding enclosures. >
542 citations
TL;DR: In this article, a number of approaches to simulating far-field source are studied, including the use of coaxial transmission line holders and a time-domain system, in each case, the system frequency range, test sample requirements, test field type, dynamic range, measurement time required, and analytical background are considered.
Abstract: Shielding effectiveness relates to the ability of a material to reduce the transmission of propagating fields in order to electromagnetically isolate one region from another. Because the shielding capability of a complex material is difficult to predict, it often must be measured. A number of approaches to simulating far-field source are studied, including the use of coaxial transmission-line holders and a time-domain system. In each case, the system frequency range, test sample requirements, test field type, dynamic range, measurement time required, and analytical background are considered. Data taken on a common set of materials are presented. >
168 citations
TL;DR: In this article, the authors considered the problem of coupling between antennas on either side of the planar mesh, and its applicability to the measurement of mesh properties is described, and the low-frequency electric and magnetic shielding afforded by mesh enclosures is considered.
Abstract: The electromagnetic shielding behavior of bounded-junction wire-mesh screens is discussed in the frequency range where the individual meshes are electrically small The screen, whose meshes are assumed to be square, is described by a equivalent sheet impedance operator The plane-wave shielding effectiveness of a planar-mesh screen is derived The problem of coupling between antennas on either side of the planar mesh is addressed, and its applicability to the measurement of mesh properties is described The low-frequency electric and magnetic shielding afforded by mesh enclosures is considered Because of the reactive character of the mesh surface, the plane-wave shielding effectiveness decreases with increasing frequency The enclosure's magnetic-field shielding effectiveness increases with increasing frequency, but saturates at a maximum value that depends on the geometry of the enclosure, the mesh size, and the mesh wire radius The enclosure electrostatic-field shielding effectiveness depends only on the enclosure and mesh geometries >
166 citations
TL;DR: In this paper, a systematic method for the diagnosis and reduction of conducted noise emissions is described, which consists of a device for determining whether the differential or common-mode component of noise is dominant along with a simplified equivalent circuit of the power supply filter for each component.
Abstract: A systematic method for the diagnosis and reduction of conducted noise emissions is described. The method consists of a device for determining whether the differential- or common-mode component of conducted noise is dominant along with a simplified equivalent circuit of the power supply filter for each component. The procedure consists of first using the device to determine which noise-component is dominant in a particular frequency range and then using the simplified equivalent circuits to determine whether an anticipated change in value of an element in the power supply filter will be effective. >
164 citations
TL;DR: In this article, two methodologies for performing shielding effectiveness measurements using mode-stirred chambers are presented, which are referred to as the discrete frequency method and the noise method.
Abstract: Two methodologies for performing shielding effectiveness measurements using mode-stirred chambers are presented. The first method, which utilizes the traditional single (discrete) frequency approach, in use at the US Naval Surface Warfare Center (NSWC) for several years, is referred to as the discrete frequency method. The discrete frequency method, as the name implies, involves testing only one frequency at a time. By contract, the second method utilizes broadband noise sources and can measure shielding effectiveness over large bandwidths with high resolution in short periods of time. The second method is referred to as the noise method. >
81 citations
TL;DR: In this paper, the problem of low-frequency shielding of a loop that is axially perpendicular to a plane shield of infinite extent is analyzed by the thin shield work of S.A. Levy (1936), solution of the vector wave equation, and application of Schelkunoff's (1934) transmission theory.
Abstract: The problem of low-frequency shielding of a loop that is axially perpendicular to a plane shield of infinite extent is analyzed by the thin shield work of S. Levy (1936), solution of the vector wave equation, and application of S.A. Schelkunoff's (1934) transmission theory of shielding. Experimental data are obtained and compared with results of using the Levy and the Schelkunoff methods in the frequency range 100-50 kHz. The first analytical technique is not general, and the limits of applicability of the results are discussed. In the second solution, which is general, expressions are derived for the total electric and magnetic fields on both sides of and within the shield. The resulting expression for shielding effectiveness is shown to agree with experimental data. The final expression for shielding effectiveness shows independence of shielding with source-to-shield spacing, a results which is shown to be consistent with experimentally obtained data. >
55 citations
TL;DR: The intrinsic electromagnetic property of a cable or connector shield is considered its surface transfer impedance as mentioned in this paper, which is the ratio of the longitudinal open circuit voltage measured on one side of the shield to the axial current on the other side (normally the outside).
Abstract: The intrinsic electromagnetic property of a cable or connector shield is considered its surface transfer impedance. This is the ratio of the longitudinal open circuit voltage measured on one side of the shield (normally the inside) to the axial current on the other side (normally the outside). In cases where a high electric field is present at the surface of the shield, the transfer admittance or charge transfer elastance is also important. Measurements of typical cables, connectors, backshells, and cable terminations are presented and explained in terms of simple models. >
53 citations
TL;DR: In this paper, the autocorrelation function, energy spectral density, and spectrum properties of a Gaussian pulse were derived for a linear array antenna, and computer plots of the derived antenna patterns were presented that show a considerable improvement in the angular resolution capability over that of the antenna patterns that have been derived for the rectangular pulse.
Abstract: The development of antenna theory for nonsinusoidal electromagnetic waves has been based on the idealized rectangular pulse. In practice, an antenna that is designed to operate in the mode of an electric hertzian dipole would radiate a pulse that best approximates a Gaussian one when the driving current consists of a linear transient. The principle of radiation of nonsinusoidal electromagnetic waves with the time variation of Gaussian pulses is discussed. The properties of the Gaussian pulse are presented, i.e., the autocorrelation function, energy spectral density, and spectrum. Antenna patterns, such as peak-amplitude pattern, peak-power pattern, energy pattern, and slope pattern are derived for a Gaussian pulse received (or radiated) by a linear array antenna. Computer plots of the derived antenna patterns are presented that show a considerable improvement in the angular resolution capability over that of the antenna patterns that have been derived for a rectangular pulse. >
46 citations
TL;DR: In this paper, the effect of resistive seams in mesh enclosures and the effects of magnetic and electric field penetration by transient fields is investigated. But the authors focus on low frequency applications and do not consider the effects on the geometry of the enclosures.
Abstract: The shielding effectiveness of an enclosure at low frequencies can be computed using a circuit approach. Not only does this technique include the effects of the properties of the shield material, but it also includes the details of the geometry of the enclosure. This approach allows a nonempirical consideration of mesh enclosures and the effects of resistive seams in enclosure walls. By working with the circuit analogue, penetration by transient fields can be computed. Essentially the enclosure is viewed as an antenna. In the case of magnetic shielding effectiveness, the enclosure is viewed as a short-circuited loop antenna. In the case of electric-field penetration, the enclosure is viewed as a fat electric dipole. Using this characterization and exact solutions where available, the current distribution on the outside of the enclosure is determined. Based on the current distribution, the penetrating fields are computed. The equations are developed in such a way as to preserve a lumped circuit analogue for the low-frequency region. The basic circuit equations for magnetic field penetration are rederived from a rigorous solution. Rules to estimate the rise time, fall time, and peak magnitudes of transient penetrating fields are developed. The electric shielding effectiveness is developed in a similar manner. >
45 citations
TL;DR: In this article, the transient response of a lossless transmission line of finite length excited externally by an electromagnetic wave of an arbitrary waveform is studied, and a solution of the transient current is obtained as a series of analytical functions.
Abstract: The transient response of a lossless transmission line of finite length excited externally by an electromagnetic wave of an arbitrary waveform is studied. By using the Laplace transformation, a solution of the transient current is obtained as a series of analytical functions. Inspection of the solution leads to the conclusion that the response currents at terminals of the line can be equivalently expressed by the components induced at both terminals, and, in addition, the multireflected wave when the line is mismatched. Furthermore, a new equivalent circuit for the coupling phenomenon is discussed. >
40 citations
TL;DR: In this paper, a set of models for both phenomena is implemented using a six-terminal network and the goal is to find out what current is induced in each terminal load of the network.
Abstract: The radiation phenomenon from a transmission line of finite length is described. Based on the hypothesis of reciprocity between the coupling of an external wave to a transmission line and the radiation from a transmission line, a set of models for both phenomena is implemented using a six-terminal network. The goal is to find out what current is induced in each terminal load of the network. The radiation characteristics of finite-length lines such as radiation fields, radiation power-density, and radiation coefficients are considered. Experiments using both straight lines and bent lines have been performed to validate the theory. >
TL;DR: In this paper, it is shown that if the boundary conditions are properly written, taking the effect of the vertical risers into account, the current distribution can be determined easily with a rather good accuracy.
Abstract: Transmission-line theory is often used to predict the current distribution along long cables parallel to the ground surface The difficulty in predicting the resonances of the structure is one of the main weaknesses of the transmission-line approach It is shown that if the boundary conditions are properly written, taking the effect of the vertical risers into account, the current distribution can be determined easily with a rather good accuracy >
TL;DR: In this article, a nonlinear model of the lightning channel is presented based on the description of the channel by a nonuniform, lossy, transmission line, and the termination at the cloud is modeled by an RC network.
Abstract: A nonlinear model of the lightning channel is presented. The model is based on the description of the channel by a nonuniform, lossy, transmission line. A nonlinear model for the losses, first developed by S.I. Braginskii (1958), is used with additional upper and lower limits. The termination at the cloud is modeled by an RC network. A numerical technique known as transmission-line modeling is used to solve the network model of lightning. The results show the strong effect of losses, cloud termination. and numerical approach on the simulated current waveshapes. >
TL;DR: In this article, a perfectly conducting uniform two-wire transmission line of finite length illuminated by a plane wave is considered, and the induced voltage and current-responses are described by analytic expressions in the frequency and time domains.
Abstract: A perfectly conducting uniform two-wire transmission line of finite length illuminated by a plane wave is considered. The induced voltage and current-responses are described by analytic expressions in the frequency and time domains. Moreover, an instructive case study is presented. This simplified and cost effective method can be an important part of the theoretical NEMP-analysis of systems. >
TL;DR: In this article, a single-element antenna measurement scheme that can simultaneously measure the electric, magnetic, and time-dependent Poynting vectors of electromagnetic (EM) fields is described.
Abstract: A unique, single-element antenna measurement scheme that can simultaneously measure the electric, magnetic, and time-dependent Poynting vectors of electromagnetic (EM) fields is described. The electric and magnetic responses of the antenna sensor are separated by a O degrees /180 degrees hybrid junction. The resulting two RF voltages, along with relative phase and frequency information, are transmitted to a remotely located vector analyzer by a pair of well-matched fiber optic downlinks. The remote receiver measures and displays the electric dipole response, the magnetic loop response, and the time phase difference between the two. This information is sufficient to determine the time-dependent Poynting vector. Both a theoretical analysis and a discussion of experimental measurements performed, which describe the capabilities and performance of a working prototype of the antenna measurement scheme, are presented. The results demonstrate that a three-axis (isotropic) version of this system could be used to measure the near fields of EM sources, as well as to completely describe the resultant flow of energy. >
TL;DR: In this paper, measurements of noise on the distribution line at power distribution substations in the frequency range from 6 GHz to 14 GHz are presented, where harmonic and background noise are omnipresent on the substation bus.
Abstract: Measurements of noise on the distribution line at power distribution substations in the frequency range from 6 GHz to 14 GHz are presented. This is the frequency range used for distribution-line communication systems by power companies for load control and feeder automation. The measurements reported here are concerned with harmonic and background noise, which are omnipresent on the substation bus. Single-frequency noise may or may not be present in a given frequency band. Impulse noise is intermittent. >
TL;DR: In this article, the radiation characteristics of a straight thin-wire antenna embedded in an isotropic chiral medium were explored, and it was shown that the radiation resistance is enhanced by the presence of chirality in the embedding medium, and the antenna LCP gain differs from the RCP gain.
Abstract: Radiation characteristics of a straight thin-wire antenna embedded in an isotropic chiral medium are explored. The radiation field contains both left-circularly polarized (LCP) and right-circularly polarized (RCP) components. The radiation pattern is found to be symmetric about the plane theta = pi /2, azimuthally isotropic, and TEM (transverse electromagnetic) in nature; however, all three of these features are found as well for isotropic achiral media. Some specific features of the radiation field on certain constant spherical surfaces are also examined. If the antenna is reduced to a point dipole, it is shown that the radiation resistance is enhanced by the presence of chirality in the embedding medium, and the antenna LCP gain differs from the RCP gain. >
TL;DR: In this article, simple equations are provided that satisfy the definitions of five of the most common transient overvoltage test waveforms: the ringwave specified in ANSI C62.41-1980, the fast transient specified in IEC 801, and the 8/20- mu s 1.2/50- µ s, and 10/1000-mu s waveforms.
Abstract: Simple equations are provided that satisfy the definitions of five of the most common transient overvoltage test waveforms: the ringwave specified in ANSI C62.41-1980, the fast transient specified in IEC 801, and the 8/20- mu s 1.2/50- mu s, and 10/1000- mu s waveforms. These equations are useful for performing computer simulations of the response of electronic circuits to transient overvoltages. >
TL;DR: In this article, the effect of the core dielectric constant on the characteristics of one-, two-, and three-turn helices driven in the axial mode is examined.
Abstract: The circuit and radiation characteristics of a helical antenna of square cross section with a dielectric core are studied. The effect of the core dielectric constant on the characteristics of one-, two-, and three-turn helices driven in the axial mode is examined. Comparisons between theory and measurement are included. >
TL;DR: In this paper, a thin-slot formalism for finite-difference time-domain (FDTD) electromagnetics codes has been evaluated in both two and three dimensions.
Abstract: A thin-slot formalism proposed by Gilbert and Holland (1981) for use with finite-difference time-domain (FDTD) electromagnetics codes has been evaluated in both two and three dimensions. This formalism allows narrow slots to be modeled in the wall of a scatterer without reducing the spatial grid size to the slot width. In two dimensions, the evaluation involves the calculation of the total fields near two infinitesimally thin coplanar strips separated by a gap. A method-of-moments (MoM) solution of the same problem serves as a benchmark for comparison. Results in two dimensions show that up to 10 percent error can be expected in total electric and magnetic fields both near ( lambda /40) and far (1 lambda ) from the gap. In three dimensions, the evaluation is similar. The finite-length slot is placed in a finite plate and an MoM surface patch solution is used for the benchmark. These data show that slightly larger errors can be expected. >
TL;DR: In this paper, the authors used an anatomically realistic model of the human torso for spatially varying leakage magnetic fields due to a 450 kHz RF induction heater and found that fairly low SARs result from leakage magnetic field on the order of 1-20 A/m that are typical of RF induction heaters.
Abstract: Calculations are presented for electromagnetic power deposition (specific absorption rates, or SARs) in an anatomically realistic model of the human torso for spatially varying leakage magnetic fields due to a 450 kHz RF induction heater. A previously described impedance method that neglects the effects of the operator's body on the source, because of weak coupling, is used for the calculations. SARs on the order of a few mu W/Kg are found for magnetic fields on the order of 1.8 A/m at the central plane of the model. This implies that fairly low SARs result from leakage magnetic fields on the order of 1-20 A/m that are typical of RF induction heaters. >
TL;DR: In this article, the interaction of natural lightning and the nuclear electromagnetic pulse (EMP) with aircraft was examined and the propositions that one can use normal exposure to lightning to provide information on EMP protection were evaluated.
Abstract: Examines the interactions of natural lightning and the nuclear electromagnetic pulse (EMP) with aircraft. The propositions that one can use normal exposure to lightning to provide information on EMP protection, and deliberate exposure to lightning to test EMP protection are evaluated. The rarity of encountering lightning, its random occurrence and variability (necessitating extensive onboard instrumentation), and its apparent deficiency in energy at the high frequencies make the use of lightning for an EMP surveillance or test impractical. >
TL;DR: In this article, the propagation characteristics of underground streets with pedestrians were analyzed using a lossy, homogeneous dielectric slab, and some numerical results for the attenuation constant and for the field distribution in the cross section were compared with experimental data.
Abstract: Radio propagation characteristics in an underground street crowded with pedestrians are presented. Measurements were carried out on vertical and horizontal polarization characteristics in a frequency range from 250 MHz to 12.4 GHz. In the analysis, the region with pedestrians is modeled as a lossy, homogeneous dielectric slab. Based on the method of effective dielectric constant, some numerical results are presented for the attenuation constant and for the field distribution in the cross section and are compared with experimental data. It is shown that the method is applicable in determining the propagation characteristics in underground streets crowded with pedestrians. >
TL;DR: A simple general relationship between the equivalent radius and the transverse line dipole moments of a narrow slot aperture having depth was shown in this article, where the cross-sectional dimensions of the aperture were assumed to be small compared to both its length and the wavelength.
Abstract: A simple general relationship is shown to exist between the equivalent radius and the transverse line dipole moments of a narrow slot aperture having depth. The cross-sectional dimensions of the aperture are assumed to be small compared to both its length and the wavelength. The general relationship can be put succinctly; the perfect magnetic cylinder, having the equivalent radius of an aperture with depth, has not only the same properties but also the same transverse line dipole moments of the aperture. >
TL;DR: The surface magnetic field attenuation of a wide range of enclosures and panels has been measured by injecting a uniform current across the surface and measuring the ratio of the surface magnetic fields to the magnetic fields inside the enclosure as discussed by the authors.
Abstract: The surface magnetic-field attenuation (MFA) of a wide range of enclosures and panels has been measured by injecting a uniform current across the surface and measuring the ratio of the surface magnetic field to the magnetic field inside the enclosure. A simple theory has been developed to explain and extend the results. The measurements show that relatively simple structures provide on the order of 50 dB of attenuation for frequencies above 1 MHz. In well-constructed enclosures, the electromagnetic performance was limited by joint resistance. Current diffusion was not evident for frequencies above a few tens of kilohertz, except in panels with minimal metal content (metal screens and flame-sprayed copper). Aperture coupling can be predicted using polarizability theory. >
TL;DR: In this article, a circular array of electric line sources for generating a uniform plane wave in the interior region of the array was analyzed, and the results for the synthesized element weightings were obtained using matrix inversion or a Fourier series technique.
Abstract: A circular array of electric line sources for generating a uniform plane wave in the interior region of the array is analyzed. Identical results for the synthesized element weightings are obtained using matrix inversion or a Fourier series technique. A physical optics approximation for the element weightings is also presented, but it yields a much poorer result for the synthesized field. The angle of arrival of the plane wave can be scanned by recalculating the element weightings, and the quality of the field is maintained. Frequency scanning is also possible, but the number of array elements limits the maximum frequency. >
TL;DR: In this article, the amount of shielding required for intrasystem compatibility can be based on local sources of interference within the system, and the equipment shield is compatible with that environment and with all other equipment having these characteristics.
Abstract: Interference in the form of extraneous noise or transients can be controlled by enclosing the circuits to be protected in an electromagnetic shield. Shielding is the primary means of protection when the source of interference cannot be controlled, although the barrier or generalized shield may be created through the use of spatial separation and orthogonalization, or may be an actual metal shield. The amount of shielding required for intrasystem compatibility can be based on local sources of interference within the system. When the equipment shield prevents the local sources from affecting its internal circuits and prevents its internal circuits from affecting the local environment, it is compatible with that environment and with all other equipment having these characteristics. This establishes intrasystem electromagnetic compatibility. >
TL;DR: In this article, a method for predicting VHF/UHF noise generated by corona on power-line conductors in steady rain has been developed, where the corona sources are modeled as electric dipoles which are randomly distributed along the conductors and driven by impulsive currents.
Abstract: A method for predicting VHF/UHF noise generated by corona on power-line conductors in steady rain has been developed. The corona sources are modeled as electric dipoles which are randomly distributed along the conductors and driven by impulsive currents. Each source induces currents on the conductors which in turn radiate as traveling-wave antennas. The receiving antenna then responds to the incoherent superposition of the fields from each source. The final formula is a function of the power-line parameters and receiving system characteristics. The most significant result is that the received noise is a strong function of the receiving antenna orientation. The noise is minimized for antennas directed at the line while it is maximized for antennas directed down the line at an angle dependent on the other problem parameters. Lower-frequency (i.e. 75 MHz) results are in good agreement with experiment. >
TL;DR: In this article, the insertion loss when the shield is inserted between two antennas, contains the properties of the antennas and receivers inextricably commingled with the property of the shield.
Abstract: Typical shielding effectiveness measurements and their relation to electromagnetic protection are reported. These measurements, which are based on the insertion loss when the shield is inserted between two antennas, contain the properties of the antennas and receivers inextricably commingled with the properties of the shield. For the assessment of electromagnetic protection, the shield's ability to limit the interaction of any arbitrary external source with an arbitrary internal circuit is found to be important. The assessment of protection cannot, in general, be obtained from insertion loss data. >
TL;DR: In this paper, some important differences between the system interactions of electromagnetic transients from lightning (LEMP) and from high-altitude nuclear explosions (HEMP) are discussed.
Abstract: Some important differences between the system interactions of electromagnetic transients from lightning (LEMP) and from high-altitude nuclear explosions (HEMP) are discussed. Interactions with small systems, such as aircraft, and large systems, such as electric power grids, are considered. Effects of factors like lightning channel attachment and the relatively local nature of the lightning excitation are contrasted with the broad-area effect of the HEMP interaction. It is concluded that although protective approaches and techniques for LEMP and HEMP are often similar, the two phenomena are sufficiently different that protection against one does not necessarily imply protection against the other. >