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Electromagnetic Compatibility, IEEE Transactions on

Issue 1 • Date Feb 1995

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Displaying Results 1 - 21 of 21
  • Catalogue of electromagnetic environment measurements, 30-300 Hz

    Page(s): 26 - 33
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    The IEEE Electromagnetic Compatibility Society's Technical Committee on Electromagnetic Environments (TC-3) has undertaken a long-term project to compile an inventory or catalogue of published measurements of electromagnetic environments. The frequency spectrum has been divided into tractable bands which will be considered one at a time. We have now completed the 30-300 Hz band. This paper presents the resulting bibliography, along with a brief overview of what has been measured View full abstract»

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  • Reduction of wave propagation loss by mesh in rectangular tunnels

    Page(s): 88 - 93
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    The reduction of radio wave attenuation in rectangular tunnels is discussed. The attenuation of the dominant mode due to its field penetration into a lossy dielectric wall is reduced by means of the attachment of wire netting (mesh). First, a reflection coefficient from a mesh screen over a lossy surface is analytically evaluated. Then, based on a geometrical optical approach to the propagation model in tunnels, the attenuation of the dominant mode in a rectangular tunnel is derived using the reflection coefficient. The calculated attenuation constants are in good agreement with experimental ones obtained in a laboratory. Finally, the efficiency of attenuation reduction rate by the mesh shielding method is summarized as a function of spatial ratio of the mesh wire interval divided by the wavelength. It is shown that the efficiency of reduction rate by mesh is significant View full abstract»

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  • Carrier-free signal design for look-down radars

    Page(s): 51 - 61
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    The detection of low flying targets with small radar cross section (RCS), known as low observables, such as cruise missiles and stealth airplanes adds a new dimension to radar signal design and radar signal processing. A high resolution look-down radar is very attractive since it takes advantage of target shape to overcome difficulties encountered with small RCS. The look-down geometry, however, imposes three requirements: 1) the radar should detect targets with small relative velocities from almost zero to about the velocity of sound with no blind speeds, 2) it should minimize ground clutter by using short pulses, and 3) the radar signal must have a thumbtack ambiguity function. We investigate a look-down radar that eliminates time side lobes of compressed signal correlation functions to improve range resolution, reduces ground clutter to enhance receiver dynamic range, and uses thumbtack resolution function to resolve moving low observable targets from the surface of the Earth. The side lobe elimination technique transforms the correlation function of a coded waveform, based on complementary codes, to the correlation function of a single pulse. Features of side lobe elimination technique along with clutter cancellation circuits are presented in terms of blind speeds and range-velocity resolution function View full abstract»

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  • Plane-wave shielding properties of anisotropic laminated composite cylindrical shells

    Page(s): 109 - 113
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    The plane-wave shielding properties of advanced composite cylindrical shells are analyzed. Based on a rigorous theory that clearly displays the propagating nature of the electromagnetic field in an anisotropic, multi-layered, and lossy cylindrical shell structure. In this study, numerical results are presented for graphite/epoxg fiber-reinforced composite shells. In particular, the parameters that influence the shielding effectiveness, such as material properties, cylinder configuration, fiber orientation, and incident wave polarization, are investigated in detail. For design purposes, an empirical formula is also proposed to estimate the shielding effectiveness in the lower frequency range. Finally, a sharp reduction of shielding performance due to resonance is also examined View full abstract»

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  • Capacitance of transmission line of parallel cylinders in the presence of dielectric coating

    Page(s): 94 - 96
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    The paper presents a method for the evaluation of variation of capacitance of a dielectric coated two-wire line of parallel cylinders, each of unit radius with a change in thickness of the dielectric along the radial direction. A conformal transformation is used to transform the conductor and dielectric boundaries to appropriate contours extending over a fixed region along the imaginary axis in the transformed plane. Approximating the continuous curve obtained through transformation of dielectric boundaries by a very large number of discrete steps, the expression for the capacitance is derived in the form of a definite integral. Numerical data on capacitance as a function of width of the dielectric in the absence and presence of a conducting ground plane are presented View full abstract»

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  • Transient plane wave coupling to bare and insulated cables buried in a lossy half-space

    Page(s): 62 - 70
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    The current induced on an infinite bare or insulated cable buried in a lossy earth medium due to a transient plane wave is presented. An exact solution is formulated in the frequency domain using a spatial transform under the thin-wire approximation. The widely used equivalent circuit transmission line model is derived from the exact solution. Results are presented for typical transmission structures under high frequency transient excitation and the exact solution is compared with the transmission line approximation. The transmission line approach provides good results for a wide range of cases. For accurate results in the high frequency situation it is necessary that the correct incident field expressions be used and that a complete representation of the earth's electrical properties (σ and ε) be retained View full abstract»

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  • Electromagnetic coupling between two half-space regions separated by multiple slot-perforated parallel conducting screens

    Page(s): 105 - 109
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    Considers the problem of electromagnetic coupling between two half-space regions separated by multiple slot-perforated parallel conducting screens. The fields are considered to be excited by either a transverse electric (TE) or a transverse magnetic (TM) plane wave. A characteristic mode solution is used for the computation of the fields in each half-space. Special attention is given to the power transmitted from one half-space to the other through the slots and to its functional dependence on various parameters. Numerical examples are presented for illustration and comparison View full abstract»

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  • Transmission through corrugated slots

    Page(s): 114 - 121
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    The transmission of electromagnetic fields through corrugated slots is studied for TE and TM polarization. A corrugated slot means that the slot is formed by a gap between two plates and that the edge walls of one or both of these two plates have grooves or corrugations running in the direction of the slot. The field solution is obtained by using the method of moments implemented as a successive inversion of the matrices associated with the unknown E-fields at the apertures between the rectangular regions forming the corrugated slot. The computer code is applied to analyze slots with corrugated edges, where the corrugations or chokes are optimized in order to make the transmission as low as possible over a given bandwidth. The results are verified by comparison with previously published results and measurements on three different slot geometries View full abstract»

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  • Capacitance calculations for cable harnesses using the method of moments

    Page(s): 131 - 137
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    A method of moments procedure to obtain the capacitance matrix for a cable harness is presented. The geometry consists of multiple, parallel, insulated wires, possibly above a ground plane. The method uses Fourier harmonic expansion functions for the total charge and Galerkin testing functions. The capacitance matrix is obtained by the relationship of free charge to potential. Computed and experimental results are presented and compared to exact analytical solutions when possible View full abstract»

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  • Induced foot-currents in humans exposed to VHF radio-frequency EM fields

    Page(s): 96 - 99
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    In order to limit the specific absorption rate (SAR) in the ankles of a person exposed to an electric field at frequencies below 100 MHz, induced current limits are prescribed in the 1992 ANSI/IEEE safety standard. The authors have measured the induced currents passing through the feet of nine subjects exposed to vertically polarized electric fields from nearby antennas, transmitting at frequencies between 90 and 104 MHz (in the FM broadcast band). The experimental results are in excellent agreement with the results obtained analytically for frequencies up to 110 MHz. The analytical results were obtained by applying the finite difference time domain (FDTD) method to an anatomically-based model of an average height male (1.75 m) and to a model of the tallest subject in the study (1.91 m). For the mean height of the nine subjects (1.75 m), the measured induced foot current for a unit strength vertically polarized electric field varied with frequency from 4.46 to 3.45 mA/(V/m) for frequencies between 90-104 MHz. For the tallest subject (1.91 m), the corresponding values ranged from 5.42 to 4.45 mA/(V/m), Foot currents in excess of the induced current limits in RF safety guidelines for both the controlled and uncontrolled environments could result even when the vertical component of the incident electric fields comply with the corresponding field limits. It is important, therefore, to not only measure the E- and H-fields, but also the induced currents up to the recommended maximum frequency of 100 MHz, and perhaps up to the upper frequency of the FM broadcast band (108 MHz) View full abstract»

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  • Development of the equivalence principle for SGEMP and source-region EMP problems

    Page(s): 84 - 88
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    This short paper develops the equivalence principle in a form useful for predicting the fields inside aperture-driven cavities. The present approach allows calculation of fields penetrating large apertures into complex cavities using a two-pass finite-difference time-domain (FDTD) procedure View full abstract»

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  • Fast-transient susceptibility of a D-type flip-flop

    Page(s): 75 - 80
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    Human electrostatic discharge (ESD) produces a transient current pulse with a very fast risetime, which can be a source of electromagnetic interference in digital devices. The focus of this paper is the radiated susceptibility of D-type flip-flops implemented in various CMOS and TTL logic technologies. A transient impulse was used to simulate the radiated field produced during an ESD event. A synchronized-disturbance testing methodology is developed that allows accurate control of the instant at which the disturbing signal is applied to the data input lines during an operational cycle of the circuit. The study reveals that these devices are susceptible only during certain time intervals during an operational cycle. The particular interval during which a flip-flop is susceptible is dependent on the logic state of the data input line, the implementation technology of the flip-flop, and the amplitude of the disturbing signal. The total width of the susceptibility intervals is a device parameter that can be used to determine the probability that the flip-flop will fail in the presence of random transient interference pulses View full abstract»

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  • Time-domain electromagnetic plane waves in static and dynamic conducting media. II

    Page(s): 17 - 25
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    For pt.I see ibid., vol.36, no.3, p.221 (1994). The electromagnetic field inside a lossy half-space for the case of a transient electromagnetic plane wave impinging on the half-space from free space is derived. The losses in the half-space are modeled by assuming either a static (J=σE) or a dynamic (τ∂J/∂t+J=σ0E) conducting medium. Solutions are derived directly from the first order system of partial differential equations, i.e. the Maxwell equations. Plots for the total fields at the half-space boundary are given and expressions for the fields anywhere inside the half-space based on these boundary fields are given. Asymptotic formulae for late and early times are derived for the case of a step function as well as a square pulse plane wave View full abstract»

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  • Required bandwidth, unwanted emission, and data power efficiency for residual and suppressed carrier systems-a comparative study

    Page(s): 34 - 50
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    This paper presents a new concept for required bandwidth along with a method for computing this bandwidth and the associated undesired emission for the classes of PCM/PSK/PM, PCM/PM and BPSK signals. The PCM/PSK/PM signals considered here employ either a square wave or sine-wave subcarrier with NRZ data format. On the other hand, the PCM/PM and BPSK signals use either a Bi-phase or an NRZ data format. Furthermore, the maximum allowable required bandwidth in the presence of noise and the data power efficiency for these modulation schemes will also be investigated. The term “data power efficiency” as considered in this paper consists of two principal components, namely, the amount of power contained in the data channel, and the symbol signal-to-noise ratio (SSNR) degradation due to the presence of intersymbol interference (ISI) for a specified required bandwidth. This paper evaluates both of these components numerically for the modulation schemes considered and the results are then compared. Furthermore, the impact of baseband filtering on the required bandwidth is also investigated in this paper View full abstract»

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  • A comparison of various measured and calculated shielding effectiveness data for a wire cage

    Page(s): 126 - 131
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    Considers the shielding effectiveness (SE) of a wire cage structure (2 m cube). The SE is predicted using various analytical approximations and measured using a number of different methods. Both near-field and far-field coupling through the mesh are considered. The results show that calculated and measured SE data can cover a large range of values depending on the configuration used. Upper and lower SE bounds for the near and far-field cases are discussed View full abstract»

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  • NEMP fields inside a metallic container with an aperture in one wall

    Page(s): 99 - 105
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    The finite-difference time-domain (FDTD) method was used to study the nuclear electromagnetic pulse (NEMP) waves coupling into one metallic container through a small aperture in one face of the container. The incident electric fields of NEMP waves were expressed by double exponential forms with two different decay constants. The time-domain behavior of the electric field inside the metallic container excited by the waves was obtained by the FDTD method. The electric field distributions on various layers for the area of the aperture of 10×10 cm2 were also calculated. It was found that the shielding effectiveness is greatly improved by a factor of 255 by reducing the area of the aperture from 10×10 to 1×1 cm2 . The aperture filled with dielectric materials was also studied for shielding effectiveness. The coupled electric field inside the metallic container was round to be a nonlinear function of the relative dielectric constant of insulators filled in the aperture View full abstract»

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  • A method-of-moments solution to the twisted-pair transmission line

    Page(s): 121 - 126
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    A method of moments (MoM) approach to modeling the unshielded, twisted-pair transmission line is developed and validated. The approach described has proven capable of predicting the operational performance characteristics of the twisted-pair transmission line, and can be implemented to analyze attenuation and crosstalk under fault conditions. The model is validated for an unfaulted transmission line by comparison with measured data as well as the classical, distributed-parameter model View full abstract»

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  • RF characterization of the semiconductor junction igniter in the 2.75 folding fin aircraft rocket

    Page(s): 80 - 84
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    The design and characterization of a novel passive ignition system which consists of a simple two-stage radio frequency (RF) low pass filter and a novel RF insensitive electro-explosive device is discussed [1]-[3]. Lumped parameter modeling was used to provide the frequency response of the circuit. The 2.75 Folding Fin Aircraft Rocket (2.75 FFAR) was utilized as a test vehicle for field measurements which were performed as specified in MIL-STD 1385B at the Naval Surface Warfare Center in Dhalgren, VA. The configuration exhibited excellent performance over the entire frequency range of 1.5 MHz to 1 GHz View full abstract»

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  • Effect of dielectric support on the inner conductor of eccentric coaxial line

    Page(s): 71 - 74
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    This paper presents a method for the evaluation of the effect of the dielectric support between the inner and the outer conductors of eccentric coaxial line. Two different conformal mappings are used to obtain two different approximate formulas for the evaluation of the capacitance of this structure. First, a cotangent hyperbolic transformation is used, which transforms the conductor boundaries to parallel straight lines, and the circle surrounding the dielectric support to a curved contour. The same structure is also analyzed using a bilinear transformation expressed in terms of mutually inverse points followed by a logarithmic transformation. In each case, an expression for the capacitance is found by replacing the continuous curve representing the dielectric boundary by a number of infinitesimally small discrete steps. A comparison of numerical data obtained by the two methods is presented View full abstract»

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  • Spatial correlation function for fields in a reverberation chamber

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    Hill, Crawford, Kanda and Wu (see ibid., vol.35, p.69, 1993) described random fields in a reverberation chamber by an integral representation of plane waves over all real angles. A physical interpretation of the random field in a reverberation chamber is that each member of the ensemble corresponds to a different stirrer (tuner) position. The plane wave spectrum representation has been found useful for providing a mathematical description for the response of a receiving antenna or other test object in a reverberation chamber and for calculating the quality factor (Q) for reverberation chambers of arbitrary geometries. This article shows that the plane wave spectrum representation of Hill et. al. can also be used to provide a simple derivation for the spatial correlation function of the fields View full abstract»

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  • On correlating TEM cell and OATS emission measurements

    Page(s): 1 - 16
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    The use of single-port broad-band TEM cells for both near-field and far-field radiated emission testing is considered. The approach is to model the radiation from the device under test (DUT) as due to an equivalent set of multipoles. Assuming the DUT is electrically small only the initial multipole moments, the electric and magnetic dipole terms, need be retained. A sequence of TEM cell measurements is then used to determine the equivalent DUT dipole moments, The dipole model then allows one to simulate DUT emissions both in free space and over a ground screen. Thus, emission measurements over an open area test site (OATS) as called for by various standards may be simulated. Such measurement schemes have previously been successfully developed for standard two port TEM cells. However, certain broad-band TEM cells are single-port devices; thus, some modification of the previous approach is required. This paper reviews the basics of the multipole model as it relates to TEM cells, details various measurement schemes appropriate to single-port TEM cells, and presents examples of measured emission data, both near field and far field, in all cases considered, the correlation between emission data measured directly over a ground screen and simulated ground screen data based on TEM cell measurements is excellent View full abstract»

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IEEE Transactions on Electromagnetic Capability publishes original and significant contributions related to all disciplines of electromagnetic compatibility (EMC) and relevant methods to predict, assess and prevent electromagnetic interference (EMI) and increase device/product immunity.

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