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Showing papers on "Electromagnetic compatibility published in 1977"


01 Jan 1977
TL;DR: In this article, the authors developed analytically tractable, experimentally verifiable, statistical-physical models of electromagnetic interference, which are invariant to the particular noise source and its quantifying parameter values, levels, etc.
Abstract: Most man-made and natural electromagnetic interference, or "noise," are highly non-Gaussian random processes, whose degrading effects on system performance can be severe, particularly on most conventional systems, which are designed for optimal or near optimal performance against normal noise. In addition, the nature, origins, measurement, and prediction of the general EM interference environment are a major concern of any adequate spectral management program. Accordingly, this study is devoted to the development of analytically tractable, experimentally verifiable, statistical-physical models of such electromagnetic interference. Here, classification into three major types of noise is made: Class A (narrow band vis-a-vis the receiver), Class B (broad band vis-a-vis the receiver), and Class C (= Class A + Class B). First-order statistical models are constructed for the Class A and Class B cases. In particular, the APD (a posteriori probability distribution) or exceedance probability, PD, vis;P1 (? > ?o)A,B, (and the associated probability densities, pdf's w1(?)A,B,[1]) of the envelope are obtained; (the phase is shown to be uniformly distributed in (0, 2?). These results are canonical, i.e., their analytic forms are invariant of the particular noise source and its quantifying parameter values, levels, etc. Class A interference is described by a 3-parameter model, Class B noise by a 6-parameter model.

129 citations


Patent
09 May 1977
TL;DR: In this article, a large resonant electric circuit is placed across an interrogation zone from an interrogation antenna and is inductively coupled to the antenna to generate secondary electromagnetic waves which cooperate with the primary electromagnetic waves from the interrogation antenna to provide improved distribution of electromagnetic field strength in the interrogation zone.
Abstract: An electromagnetic article detection system of the type wherein a target having frequency selective electrical characteristics produces predetermined electromagnetic effects in response to an alternating electromagnetic field. A large resonant electric circuit is placed across an interrogation zone from an interrogation antenna and is inductively coupled to the interrogation antenna to generate secondary electromagnetic waves which cooperate with the primary electromagnetic waves from the interrogation antenna to provide improved distribution of electromagnetic field strength in the interrogation zone.

46 citations


Journal ArticleDOI
TL;DR: In this article, the authors describe the development of an electromagnetic simulator for accurate generation of broadband suspectibility test fields within a shielded environment, which consists of a large, 3 m X 3m X 6 m, rectangular transverse electromagnetic (TEM) transmission cell that is loaded with RF absorber to suppress multimoding at frequencies above the cell's waveguide cutoff or resonant frequencies.
Abstract: This paper discusses the development of an electromagnetic simulator for accurate generation of broad-band suspectibility test fields within a shielded environment. The simulator consists of a large, 3 m X 3 m X 6 m, rectangular transverse electromagnetic (TEM) transmission cell that is loaded with RF absorber to suppress multimoding at frequencies above the cell's waveguide cutoff or resonant frequencies. The paper describes the measurement facility and technique, and the experimental verification of pertinent test paramenters such as system VSWR, insertion loss, and test field uniformity. The measurement system is anticipated to provide swept, automated susceptibility measurements of electronic equipment to CW, pulsed, and EMP fields within the frequency band, 10 kHz to 1 GHz.

18 citations


Patent
03 Feb 1977
TL;DR: In this paper, a special combination of electromagnetic interference shields was proposed to reduce the electromagnetic interference from an electrical power supply circuit incorporating an inverter and transformer windings there within which normally constitute sources of unwanted electromagnetic interference signals unless suppressed.
Abstract: Electromagnetic interference shields are connected to electrical reference points from specially selected null or "center tap" connection points where noise voltages induced in the surface of the electromagnetic shield are substantially balanced out such that injection of such induced interference noise voltages to the connected reference points are substantially reduced. Special selection of isolated reference points for the input and output circuits as well as a special combination of electromagnetic interference shields substantially reduces the electromagnetic interference emanations from an electrical power supply circuit incorporating an inverter and transformer windings therewithin which normally constitute sources of unwanted electromagnetic interference signals unless suppressed.

16 citations


Journal ArticleDOI
TL;DR: In this paper, the inner side of the shield with a special resistive paint, which reduces the Q factor of the resonant cavity, has been used to suppress the interference.
Abstract: The electromagnetic screening of High Voltage laboratories against external interference is required in order to facilitate measurements inside the laboratory of partial discharges and radio interference voltages during dielectric testing. Such laboratories have been found to behave as high quality cavity resonators when excited from inside by the rapid discharges of impulse generators. Due to the large physical dimensions of high voltage halls, some resonant frequencies may be as low as a few megahertz. The oscillatory electromagnetic fields produced by the currents which circulate in the cavity induce stray signals in the impulse voltage measuring circuits. Such circuits usually have pass-band widths sufficiently large to reproduce these oscillations. This interference is then superimposed on the impulse oscillograms and, in certain circumstances may hamper the interpretation of the test voltage oscillograms. The interference can be suppressed by coating the inner side of the shield with a special resistive paint, which reduces the Q factor of the resonant cavity. Although such paint is not yet commercially available the method has been experimentally verified on a reduced scale model.

7 citations


Journal ArticleDOI
TL;DR: The proposed uses of a spectrum measurement capability are categorized as measurements to determine spectrum occupancy, check for and document compliance with assignment rules, regulations, and standards, and facilitate electromagnetic compatibility among the various systems using the radio spectrum by helping solve specific EMC-related problems.
Abstract: This paper defimes a spectrum measurement capability that will be directly useful to the managers of the radio-frequency spectrum. The proposed uses of such a capability are categorized as measurements to 1) determine spectrum occupancy, 2) check for and document compliance with assignment rules, regulations, and standards, and 3) facilitate electromagnetic compatibility (EMC) among the various systems using the radio spectrum by helping solve specific EMC-related problems. Both general and specific requirements are identified. The hardware and software for a spectrum measurement system (SMS) which can satisfy these requirements are described at the functional level.

7 citations


01 Nov 1977

6 citations


01 Sep 1977
TL;DR: In this article, the IEMCAP code can successfully predict the EMC performance characteristics of a modern Air Force weapon system, using the F-15 aircraft as the measured baseline for comparison.
Abstract: : This validation effort effectively demonstrates that the IEMCAP code can successfully predict the EMC performance characteristics of a modern Air Force weapon system. In this validation, using the F-15 aircraft as the measured baseline for comparison, the IEMCAP predicted the overall system compatibility, some isolated cases of interference, and the compatibility effectiveness of the subsequent fixes. Numerically, this means that for 353 coupling pairs in some three major coupling modes (wire-to-wire, antenna-to-antenna, and antenna-to-wire), IEMCAP successfully predicted 303 cases of compatibility, 7 cases of interference, ( and the effectiveness of their subsequent fixes), and 43 Type I errors in which the code predicted interference when actual compatibility was present. There were no Type II errors in the analysis in which compatibility was predicted when interference was present. With this validated computerized analysis program, Air Force product divisions and their system contractors can facilitate the practical implementation of EMC design-to-cost at all stages of an Air Force system's life cycle with the attendant scheduling, testing, and cost benefits. This effort supports technical program objective CCC survivability (TPO 6RIC). (Author)

6 citations


Journal ArticleDOI
TL;DR: In this article, a measure of the compatibility during co-channel operation, called circuit compatibility, was introduced, which is the ratio of the estimated circuit reliability considering the operation of an interfering transmitter (without considering other potential interferers).
Abstract: A technique for computing the electromagnetic compatibility of HF sky-wave communication systems is described. The circuitreliability methodology,-normally used to estimate expected circuit performance in the absence of interference, has been extended to estimate the expected performance in the presence of sky-wave interference. A measure of the compatibility during co-channel operation, called circuit compatibility, is introduced. Circuit compatibility is the ratio of the estimated circuit reliability considering the operation of an interfering transmitter (without considering other potential interferers) to estimated circuit reliability under interference-free conditions. The techniques involved to estimate circuit compatibility include the determination of 1) the probability of simultaneous transmission by the desired and interfering transmitters, 2) the joint probability that the standard MUF's on the desired and interfering paths are above their operating frequencies, and 3) the joint probability that the signal-power-to-noise density ratio is above the receiver's required signal-power-to-noise density ratio for the desired grade of service and that the signal-to-interference is above the signal-to-interference threshold for the desired emission against the interfering emission. The last two probabilities are represented by the bivariate normal distribution. The model is generalized to include problems other than sky-wave communications for frequencies at HF and above.

6 citations



Journal ArticleDOI
N. Ari1
TL;DR: In this paper, a theoretical and experimental study of induced voltages in high voltage test circuits is presented, which are produced by electromagnetic radiation fields arising from travel - ling waves (current and charge) along the lead in the measuring system.
Abstract: This paper deals with the theoretical and experimental studies of induced voltages in high voltage test circuits. These induced voltages are produced by electromagnetic radiation fields arising from travel - ling waves (current and charge) along the lead in the measuring system. These travelling waves are known to exist. The radiation fields can be calculated by applying distribution theory to the wave equations. All the relevant phenomena are presented and discussed for a measuring system in an indoor U.H.V. Laboratory. This contribution gives some explanation to questions of measurement phenomena and represents the first fundamental study of this topic.

Proceedings ArticleDOI
01 Aug 1977
TL;DR: In this article, electric field strength measurements are reported for the near-field inside and outside of a passenger vehicle and of a tractor-trailer vehicle with all common combinations of mobile transmitters and antennas.
Abstract: As the number of electronic systems used on vehicles increases, the need to know the electromagnetic environment in and around these vehicles increases. This knowledge becomes basic information needed by system designers to avoid electronic system failures. Results of electric field strength measurements are reported for the near-field inside and outside of a passenger vehicle and of a tractor-trailer vehicle. These measurements were made with all common combinations of mobile transmitters and antennas. The rf transmitting sources used the maximum legal output power (110 W) at 40, 162, and 416 MHz, and nominal 100 watt power levels in the HF band (3 to 30 MHz). Illegal power levels (about 100 watts) of CB transmissions at 27 MHz were used through a special authorization by the Interagency Radio Advisory Committee (IRAC).

Proceedings ArticleDOI
01 Aug 1977
Abstract: This paper describes an automated frequency assign­ ment system (FAS) built under contract to NATO for the purpose of assigning frequencies to Air/Ground/Air and Air/Air voice communication circuits in the frequency band from 225 MHz to 400 MHz. The FAS makes use of cosite and intersite engineering criteria to select compatible frequencies in a spectrum conserving manner. After a period of test and evaluation, the FAS was used to generate a new assignment plan for over 6,000 assignment requests. The results obtained show Clearly the advantage of efficient automated assignment tech­ niques over previous manual methods.

Journal ArticleDOI
TL;DR: In this article, a transit car equipped with a chopper-controlled dc propulsion system was tested on the third-rail fed test track at the General Electric plant in Erie, PA. The measured values of the radiated interference showed significant disagreement with the calculated values.
Abstract: Analysis and measurement of radiated and conducted electromagnetic interferences were performed on a transit car equipped with chopper-controlled dc propulsion system. The measured values of the radiated interference showed significant disagreement with the calculated values. It was determined from the analysis of the measured data that the voltage drop caused by the dc propulsion-current harmonics contributed to the discrepancies. Extensive tests on the ?-mi (1.2-km) long third-rail fed test track at the General Electric plant in Erie, PA, showed that the interference levels generated from the chopper-controlled propulsion equipment are acceptable. However, it is felt that the existing and impending electromagnetic compatibility (EMC) standards are, in some instances, neither technically sound nor realistic. Suggestions are made for the improvements of standards and measurement procedures.

Patent
22 Nov 1977
TL;DR: In this paper, a method of converting the carrier frequency of an incoming electromagnetic wave spectrum in an electromagnetic energy receiver comprising a converter, whereby the energy of the electromagnetic waves received by the receiver is accumulated in the input resonant system of the aforementioned converter which is frequency-selective and can be returned in the operating frequency range of this receiver.
Abstract: A method of converting the carrier frequency of an incoming electromagnetic wave spectrum in an electromagnetic energy receiver comprising a converter, whereby the energy of the electromagnetic waves received by the receiver is accumulated in the input resonant system of the aforementioned converter which is frequency-selective and can be returned in the operating frequency range of this receiver The electromagnetic energy is accumulated either directly in the material of the semiconductor, in particular, dielectric element used in the above input resonant system, or in a resonator which is contained in the same input resonant system and is built on sections of a lumped- and/or distributed-parameter line and which includes a semiconductor element The electromagnetic characteristics of the semiconductor element depend on the electromagnetic parameters of constant and variable magnetic and electric fields acting upon this element A periodic time change in the magnitude of the incoming electromagnetic energy accumulated in the input resonant system of the converter, ie auxiliary power modulation of the incoming electromagnetic waves, is brought about by selecting appropriate electromagnetic parameters of the constant and variable magnetic and electric fields acting upon the material of the aforementioned semiconductor element An electromagnetic energy receiver comprising at least one converter and an output device connected in series The converter is made in the form of an input resonant system and an output resonant system connected by means of a spatial detection system; the input resonant system comprises at least one semiconductor element and is tuned to the time-average value of the carrier frequency of the incoming electromagnetic waves, while the output resonant system is tuned to a frequency which is a multiple of the time-constant frequency of the auxiliary power modulation imposed on the incoming electromagnetic waves The invention is intended for application mainly in the field of radio physics and electronics

ReportDOI
01 Jan 1977
TL;DR: In this article, the authors explore all possible sources regarding electroexplosive devices including visits to principal laboratories that have conducted tests on these devices to ascertain if further testing is necessary to determine their susceptibility to electromagnetic pulses.
Abstract: : The object of this report is to explore all possible sources regarding electroexplosive devices including visits to principal laboratories that have conducted tests on these devices to ascertain if further testing is necessary to determine their susceptibility to electromagnetic pulses.





Proceedings ArticleDOI
01 Aug 1977
TL;DR: An overview of NCAP's c h a r a c t e r i s t i c s , d iscu sses r ecen tly incorporated improvements, and o u t l in e s plans fo r i t s future growth are presented.
Abstract: In recen t years the computer has become a valuable tool for performing EMC a n a ly s is . S op h is t ica ted com­ puter codes have been w r itten to provide a wide v a r ie ty o f c a p a b i l i t i e s . This paper d iscu sses one o f these computer codes , the Nonlinear C ircu it A nalysis Program (NCAP), which has recen tly become a part o f the United S ta tes Air Force's arsenal o f a n a ly t ica l programs. This paper i s an overview o f NCAP's c h a r a c t e r i s t i c s , d iscu sses r ecen tly incorporated improvements, and o u t l in e s plans fo r i t s future growth.

01 Jan 1977
TL;DR: In this article, the authors present results of investigations made in the U.S.R. during a number of years directed at the improvement of electromagnetic environment along the routes of electric transport.
Abstract: Urban land and railway electric transportation supplied from overhead d.c. and a.c. contact-conductor mains is a source of intensive quasi-impulsive interference in a broad frequency band. This report presents results of investigations made in the U.S.S.R. during a number of years directed at the improvement of electromagnetic environment along the routes of electric transport. The investigation aimed to improve broadcast and television reception as well as improving the conditions of service radio communication at the electric transport.


01 Jan 1977
TL;DR: In this paper, a Fourier analysis of the current in the electrical power lines is performed to calculate the induced voltages in the telecommunication cables in the subway in Vienna/Austria.
Abstract: For the subway in Vienna/Austria electrical drives for air flow control are considered whose speed is controlled by power electronic circuits. The electric power line feeding the power electric circuits is mounted in parallel with the subway telecommunication cables over a length of close to six-hundred meters. The current pulses -- caused by the power electronic control -- in the electric power line lead to induced voltages in the telecommunication cables. This paper provides a derivation of equations to calculate the induced voltages. A Fourier analysis of the current in the electrical power lines is performed. The difficult problem of calculating the induced voltages in the telecommunication cables is solved by the conform mapping. The real geometric configuration concerning magnetic field calculation. In this configuration, by different mathematical operations, the induced voltages can be calculated. Good comparison is found between calculation and measurement of induced (EMI) voltages.

01 Jan 1977
TL;DR: Integral-equation and numerical techniques are used to determine guidelines in valid electromagnetic compatibility (EMC) testing of missiles, using thin-wire and body-of-revolution modeling to establish guidelines on testing validity.
Abstract: Integral-equation and numerical techniques are used to determine guidelines in valid electromagnetic compatibility (EMC) testing of missiles. Both thin-wire and body-of-revolution modeling are used. Investigated are two primary aspects. 1) If a near-zone source is used rather than plane-wave incidence, how far must the source be for valid simulation, and 2) how significant is the presence of the rocket exhaust (or plume) in determining subsystem response, and need it be included for valid EMC testing? The simulation validity conclusions reached for the models without apertures apply directly as well to the real-life body with apertures. Numerical results are given over the frequency range of 50-200 MHz to help establish guidelines on testing validity.

Proceedings ArticleDOI
01 Aug 1977
TL;DR: In this article, a compact pulsed-power generator is described, which is capable of feeding power into a 50-ohm load at 10 kV peak and operates on the principle of a large capacitance discharging into a spark gap, giving a damped sinusoidal output.
Abstract: A compact pulsed-power generator is described, which is capable of feeding power into a 50-ohm load at 10 kV peak. It operates on the principle of a large capacitance discharging into a spark gap, giving a damped sinusoidal output. The theory of operation is given, and construction of the device outlined. The experimental setup is described and voltage curves of the output, both theoretical and experimental, are given. Points of agreement between theory and exper­ iment are noted, and the differences explained and discussed. The frequency of oscillation is around 23 MHz. One of the many possible uses could be the testing of the behavior of antennas under transient conditions. Another use could be direct injection of power into cable and electronic systems to measure the effects of electromagnetic interference, for the purpose of hardening such systems against EMI. The major advantages of this generator are ease of construction, low cost, compactness and portability, along with its high-voltage output. INTRODUCTION The circuit of Figure 1 is described by the fol­ lowing equations: 1 di3 (t) _ li(t)at + L _ _ o 0 (la) ^ J i^tjdt J i2 (t)dt Ri2 (t) = 0 (lb) ^ (t) + i2 (t) = i3 (t) . (lc) Current directions are given in Figure 1. Taking Lap­ lace transforms of Equation (1), we have: I (s) q (0) -------------LsI3 (s> Ll3 (0) = 0 <2a) i (s) q.fo) I2(s) g2 (°) c T " ' c T " c T ~ + ri2 (s) = 0 (2b) I^s) + I2 (s) = I (s) , (2c) The theory of operation of the pulse generator will be given. Construction of the generator and the operation of its power supply will be described. The experimental layout will be shown, and output voltage waveforms, both theoretical and experimental, will be given. Differences between theory and experiment will be explained, and possible uses for such a pulse gen­ erator will be outlined.


Proceedings ArticleDOI
01 Aug 1977
TL;DR: In this paper, a statistical description of the response of a long, cylindrical enclosure illuminated by a plane wave of arbitrary incidence and over a wide frequency range is presented, where the particular frequency range of inter- est is such that the length of enclosure is comparable to the corresponding wavelnegth in space, while the radius is small compared to the wavelength.
Abstract: In evaluating the EMC performance of enclosure systems, one frequently encounters the question concern­ ing the shielding effectiveness of a long, metallic, cylindrical enclosure over a wide frequency specture [1]. It is clear that while the skin effect is usually the dominant factor in determing the low frequency response, penetration into the enclosure through small holes, cracks and other openings is largely responsible for causing interferences with internal electronic circuitries at higher frequencies. Usually one does not have a precise knowledge regarding the location of the entry point, nor the interference frequency and incident angle even though it is logical to assume that the interference signal usually arrives in a form of plane waves illuminating the enclosure. In this paper, a statistical description of the response of a long, cylindrical enclosure illuminated by a plane wave of arbitrary incidence and over a wide frequency range, is presented. The particular frequency range of inter­ est is such that the length of enclosure is comparable to the corresponding wavelnegth in space, while the radius is small compared to the wavelength. Using a coaxial cylinder to model the enclosure and the cable inside the enclosure, we have computed the induced current at a load, in addition to the skin current on the enclosure. Effects of the internal resonances (of the coaxial cylinder) and the external resonances are then discussed in detail.

Journal ArticleDOI
TL;DR: The U. S. Army, with engineering assistance from the U.S. Department of Commerce, has developed a powerful new tool which will significantly enhance the ability to ensure operational electromagnetic compatibility (EMC) among existing and planned communications facilities as mentioned in this paper.
Abstract: The U. S. Army, with engineering assistance from the U. S. Department of Commerce, has developed a powerful new tool which will significantly enhance the ability to ensure operational electromagnetic compatibility (EMC) among existing and planned communications facilities: the transportable, automated EMC measurement system (TAEMS). The TAEMS is a self-contained, self-propelled, air/ground transportable, fully automated measurement and analysis facility, designed to perform frequency and time domain measurements of the electromagnetic environment over the range of 20 Hz-40 GHz. Innovative system design features are discussed, and selected system performance characteristics are described.

Proceedings ArticleDOI
01 Aug 1977
Abstract: In th is paper, a m athem atical form ula is developed to calculate th e shielding effectiveness of cu rren t missile structu re . The for­ mula) based on th e work of H arrington, Jordan , and S tra tton , is th en com pared to Schelkunoff s form ula, which was modified by extending from sm all to large cylinders. A design concept is next developed and applied to an a ir vehicle. Finally, experim ental d a ta of predicted and m easured values of shielding effectiveness is presented. Introduction