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Electromagnetic Compatibility, IEEE Transactions on

Issue 4 • Date Nov 1989

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Displaying Results 1 - 16 of 16
  • Influence of microwave scattering by power transmission lines on digital radio communications

    Page(s): 346 - 352
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    A method for evaluating power transmission line interference with microwave radio communication circuits due to microwave scattering is presented and used to predict digital radio transmission performance degradation. Numerical results show that the effects of power line screening on highly efficient digital radio systems are more serious than on analog (FM) radio systems since power lines cause quadrature distortion and intersymbol interference as well as average level reduction. An experimental result using a communication satellite beacon shows that conductors within the first Fresnel zone cause the interference View full abstract»

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  • Comparison of theoretical and experimental data for the near field of an open-ended rectangular waveguide

    Page(s): 353 - 358
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    A comparison of theoretical and experimental data on the radiating near field of an open-ended waveguide (OEG) is presented. Two theoretical methods are examined. The first is an approximation based on simple plane-wave equations with the electric field expressed in terms of the gain of the OEG. The gain equation is an empirical equation obtained from scaled measured data. The second approach is based on far-field-to-near-field transformations. Its purpose is to provide an alternate method for computing the fields as well as a means of assessing the accuracy of the first approach. Theoretical data computed using both methods are presented along with measured data obtained in the anechoic chamber. The discrepancy between the two theoretical approaches is typically less than 0.5 dB and increases with the distance between the OEG and the field point. For the measured data, ripples attributed to internal reflections in the chamber are observed. Also observed was a trend whereby the measured data fell consistently below the expected value for r⩾3λ. Although the cause of this trend is difficult to isolate without additional experimental work, it is believed to be due to the measurement setup and not by the near-field effect of the OEG View full abstract»

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  • Principles of high-resolution radar based on nonsinusoidal waves. I. Signal representation and pulse compression

    Page(s): 359 - 368
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    Carrier-free coded waveforms that promise good clutter rejection and high-resolution capabilities for radar are represented as a sequence of positive and negative Gaussian pulses. On the basis of this signal representation, the matched-filter (or correlated receiver) response to carrier-free coded waveforms is analyzed and plotted for certain Barker and complementary codes, complementary-code pairs being the optimum codes for clutter rejection. The systematic design of a carrier-free, pulse-compression radar system is described. A correlator receiver that is specifically designed for the selective reception of complementary-code pairs is presented. Computer simulation results for the correlator receiver are also presented View full abstract»

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  • Measurements of BART magnetic fields with an automatic geomagnetic pulsation index generator

    Page(s): 413 - 417
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    Measurements of the large-amplitude magnetic field fluctuations produced by the San Francisco Bay Area Rapid Transit (BART) system using an automatic computer-based geomagnetic pulsation index generator located on the Stanford campus, which is approximately 40 km from the center of the BART system, are described. Because the temporal variation of the fluctuations is well defined on an hour-to-hour and day-to-day basis, due to the transit system scheduling, they provide a convenient means for evaluating the performance of the index generator. The index generator, in turn, provides new information about the frequency content of the BART field fluctuations, and it can be used, in a general sense, to monitor activity on the BART system View full abstract»

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  • Accuracy of approximate transmission line formulas for overhead wires

    Page(s): 396 - 397
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    Errors resulting from two approximations of the transmission line parameters of overhead wires are determined. Sunde's simple approximation (1968) is found to be more accurate than the Hankel function approximation View full abstract»

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  • Principles of high-resolution radar based on nonsinusoidal waves. II. Generalized ambiguity function

    Page(s): 369 - 375
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    For pt.I see ibid., vol.31, no.4, p.359-68 (1989). A generalized ambiguity function for nonsinusoidal coded waveforms that are represented as a train of properly weighted Gaussian pulses is derived and analyzed to study its properties. Computer plots of generalized ambiguity functions of different binary codes, e.g. Barker, complementary, and pseudorandom codes, are presented. The various computer plots show that the desired thumbtack ambiguity function is achievable by nonsinusoidal coded waveforms View full abstract»

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  • A transmission line model of cable to antenna coupling inside a screened room

    Page(s): 397 - 404
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    A coupled-transmission-line model that evaluates the coupling of emissions from a cable to an antenna when both are located within a screened room is presented. The cable is positioned over a conducting bench in the room. The model developed is valid over the frequency range 10 kHz to 30 MHz. Its parameters can be found quickly and can be easily adjusted to account for changes in height, length, location across the bench, and radius of the cable. A method for evaluating the coupling parameters of the model is given. It involves the use of conformal transformations and image techniques View full abstract»

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  • On using a sense wire to quantitate the magnetic flux leakage through an aperture in an electromagnetic shield

    Page(s): 337 - 341
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    A formulation is developed for determining the sensitivity of positioning a sense wire behind an aperture in an electromagnetic shield to quantitate the flux leakage through the aperture. Both hardened and unhardened circular apertures are considered. Comparisons with measured data are made to verify the analysis View full abstract»

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  • Reply to comments on Wait's `In defense of J.A. Stratton'

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    The author points out that M.G.M. Hussain (ibid., vol.31, no.3, p.202, May 1989), in his comments on the author's paper (ibid., vol.30, no.4, p.590, Nov. 1988) says that equation (4) is not valid at y=0. He notes that he stated that y>0. Even if the source were a current sheet in the plane y=0, it would still be possible to alloy y to approach zero from positive values View full abstract»

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  • Hazard of low-frequency electromagnetic coupling of overhead power transmission lines to electroexplosive devices

    Page(s): 393 - 395
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    The purpose of this investigation was to determine whether the fields generated by overhead transmission lines and stations pose a hazard to electroexplosive devices (EEDs). An analysis showed that under worst-case conditions, the maximum induced current in an EED resulting from power-line coupling is approximately 6.3 mA for the case of electric field coupling and 0.67 mA for the case of magnetic field coupling. The no-fire levels of numerous devices including, but not limited to, impulse cartridges, blasting caps, detonations, flares, switches, and pressure cartridges were compared to determine the most sensitive. It was concluded that worst-case coupling assumed in the analysis is insufficient to induce a hazardous current level in an EED View full abstract»

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  • Frequency spectra of the arc current due to opening electric contracts in air

    Page(s): 342 - 345
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    Frequency spectra of the electromagnetic noise due to arc current caused by Ag contacts upon opening in air at atmospheric pressure are described. To take into consideration the fast transients and high-frequency discharge phenomena at the contacts, a distributed constant model consisting of relay contacts and a coaxial distributed constant line is introduced. An experiment carried out under conditions of low circuit current (3.84 A) and low source voltage (48 V) is reported. The results indicate that the frequency spectra of the arc currents depends on the length and terminal conditions of the line connected to the contacts View full abstract»

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  • An approximate approach for the inductance coefficients of an electric circuit containing a number of branches

    Page(s): 390 - 393
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    An approximate approach for calculating the inductance coefficients of an electric circuit containing a number of branches is derived from the definition of an inductance coefficient of a single loop. An equivalent circuit is then developed to calculate the current distribution when lightning strikes a launch tower system. A numerical example is given. The computed results are consistent with the results of test measurements View full abstract»

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  • A method to optimize the direction and measurement of EMI signals

    Page(s): 409 - 413
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    The detection and measurement of electromagnetic interference (EMI) signals using conventional EMI receivers and spectrum analyzers is discussed. A statistical approach is used to demonstrate that the probability of detecting a single signal increases as the receiver sweep rate increases. This is then demonstrated in the more general case of multiple signals. Signal density is defined by the Poisson random variable, and an equation is derived that relates the probability of detection to signal density and receiver sweep rate. Also discussed is the choice of types of receivers and detectors that will ensure a maximum probability of detection. A sequential process that first detects signals with a high degree of probability and then performs an accurate measurement of their amplitude and frequency is described View full abstract»

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  • An analysis of the transient fields of linear antennas

    Page(s): 404 - 409
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    Theoretical solutions for transient radiation from traveling-wave linear antennas were published recently by Chen (see ibid., vol.30, p.80-3, 1988), but the results have some mistakes, and the methods are tedious. A solution in which each term has obvious physical meaning is obtained here in a simple and direct way. The characteristics of the solutions are discussed and compared with strict numerical results. In the time window, the solutions are of a simple form, and their natures are independent of distance. The transient far-field conditions are obtained directly in the time domain View full abstract»

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  • EMI-immune thermocouple thermometry in RF hyperthermia systems

    Page(s): 384 - 389
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    The authors outline the advantages of using thermocouple thermometry for temperature monitoring during localized electromagnetic hyperthermia. Problems faced in used metallic probes during RF power delivery are discussed from both theoretical and practical points of view. Solutions to electromagnetic interference (EMI) problems are suggested, and the actual implementation of an EMI-immune thermometric system suitable for temperature monitoring in RF hyperthermia is described View full abstract»

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  • An experimental test of a theory of lightning-induced voltages on an overhead wire

    Page(s): 376 - 383
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    Measured and calculated voltages induced on an unenergized overhead power line by lightning return strokes at distances greater than 5 km from the line are presented. The experiment was performed at the NASA Kennedy Space Center during the summer of 1985 and involved the simultaneous measurement of the voltage induced at one end of the top phase of a three-phase power line and the two horizontal components of the return-stroke magnetic field incident on the line. The effective ground conductivity was determined from previous simultaneous measurements of the vertical and horizontal electric fields. Experiments were performed for two cases: (1) all phases of the power line open-circuited, and (2) one end of the top line terminated at 600 Ω with the other end open-circuited and the other two phases open-circuited at both ends. The waveshapes of the measured and calculated voltages are in reasonably good agreement, and the reasons for observed discrepancies are discussed View full abstract»

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Aims & Scope

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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Editor-in-Chief
Professor Farhad Rachidi
Swiss Federal Institute of Technology (EPFL)
EMC Laboratory
CH-1015 Lausanne
Switzerland
Phone: +41 (0) 21 693 26 20 (direct)
+41 (0) 21 693 26 61 (secretariat)
Fax: +41 (0) 21 693 46 62
Email: Farhad.Rachidi@epfl.ch
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