Showing papers on "Electromagnetic compatibility published in 1994"

A low-frequency model for wedge or pyramid absorber arrays-I: theory

Abstract: The interaction of electromagnetic waves with an array of absorbing wedges or pyramid cones is studied in the low-frequency limit; i.e., when the period of the array is small compared with wavelength. A theoretical model is obtained using the method of homogenization, which replaces the transversely periodic structure with a transversely uniform medium possessing a certain (generally anisotropic) effective permittivity and permeability. Plane-wave reflection from such structures can then be modeled using well-known techniques for one-dimensionally inhomogeneous media; a Riccati equation for the reflection coefficient is used in this work. This model is appropriate for use with absorbers found in anechoic chambers used for electromagnetic compatibility and electromagnetic interference (EMC/EMI) measurements over the frequency range of 30-1000 MHz. >

EMTP-based model for grounding system analysis

Abstract: EMC and lightning protection analyses of large power systems require the knowledge of the dynamic behavior of extended grounding systems. They cannot be regarded as equipotential planes, but must be treated as coupling paths for transient overvoltages. This contribution presents a model for linear earth conductors based on the transmission line approach and outlines its integration in the transients program EMTP. Validation of the presented model is achieved by comparison with field measurements and with a rigorous electromagnetic model. Overvoltages and electrical fields throughout electrical power systems can thus be computed. >

A Handbook for Emc Testing and Measurement

Abstract: During the 1980s the worldwide interest in electromagnetic compatibility (EMC) grew rapidly with the introduction of legislation to control the growing interference problems generated by the increased use of electronic equipment in industry and in the home. The European directive harmonising EMC measurements gave particular impetus to manufacturers and importers of electrical and electronic equipment in Europe to understand EMC design techniques and verification procedures. This book explains how equipment can be verified by testing. It discusses the nature of EMC standards world wide and describes in detail testing methods and their conduct and accuracy. In addition to standard EMC testing, topics including electrostatic discharge, nuclear electromagnetic pulse and lightning are also discussed. In the broad span of its subject matter, the interests of equipment manufacturers, EMC test engineers, project managers and company administrators are addressed. The testing of both military and commercial electronic equipment is covered. Particular emphasis is placed on the nature of EMC test equipment and how to use it to make reliable measurements.

Transient electromagnetic interference in substations

Abstract: Electromagnetic interference levels on sensitive electronic equipment are quantified experimentally and theoretically in air and gas insulated substations of different voltages. Measurement techniques for recording interference voltages and currents and electric and magnetic fields are reviewed and actual interference data are summarized. Conducted and radiated interference coupling mechanisms and levels in substation control wiring are described using both measurement results and electromagnetic models validated against measurements. The nominal maximum field and control wire interference levels expected in the switchyard and inside the control house from switching operations, faults, and an average lightning strike are estimated using high frequency transient coupling models. Comparisons with standards are made and recommendations given concerning equipment shielding and surge protection. >

A low-frequency model for wedge or pyramid absorber arrays-II: computed and measured results

Abstract: Based on the theoretical model developed in Part I of this two-part paper, we present numerical results for the plane-wave reflection coefficient from arrays of pyramid-cone absorbers when the period of the array is smaller than half a wavelength. Comparison is made with results of a moment-method calculation, as well as with experimental measurements. The model is then used to modify the design of some existing types of commercially available absorbers for reduced reflection in the frequency range of 30-300 MHz. These improved absorbers have been installed in an anechoic chamber used for electromagnetic compatibility and electromagnetic interference (EMC/EMI) measurements. Site attenuation measurements from this chamber are presented which show closer correspondence to an ideal open-field test site. >

Calculation of radiated electromagnetic fields from cables using time-domain simulation

Abstract: Radiated electromagnetic fields are produced by currents in cables or transmission lines interconnecting various circuits. An elegant method of computing the resultant electromagnetic field, produced by several radiating current elements, is given. The current in each radiating cable is first found from a time-domain simulation algorithm and this may be a steady-state or transient current. The radiated field is then calculated by assuming that a radiating transmission line can be treated as a chain of short radiating dipoles. The problems associated with the calculation of the near-zone term at low frequencies and the overall response near the radiator are clarified. The proposed technique is fully evaluated and compared with other methods. >

Field penetration into metallic enclosures through slots excited by ESD

Abstract: The coupling through apertures between an electrostatic discharge (ESD) current flowing on the external shield of a metallic enclosure and the electromagnetic field of its internal region is analyzed; the excitation of the electric field on the apertures by the ESD and then the evaluation of the internal field are calculated separately, by means of the finite difference time domain (FDTD) technique and the modal expansion, respectively. All the numerical results obtained with this simple and numerically efficient approach have been validated by measurements. >

Electromagnetic noise absorbing material and electromagnetic noise filter

Abstract: Electromagnetic noise absorbing material and filter, which are small, light, and effective even with respect to unwanted electromagnetic waves of a few hundred MHz or more, are provided. A small and flexible electromagnetic noise filter cable and tape-shaped electromagnetic noise filter, as well as a manufacturing method and manufacturing apparatus therefor, are also provided. The electromagnetic noise absorbing material has a thickness or particle diameter of the alloy magnetic substance which is within a range of from 1/10 to 10 times the skin depth thereof, and thereby, a large eddy current loss can be generated, so that it is possible to manufacture electromagnetic noise filters having various shapes, which are small, light, and which realize a large electromagnetic noise suppression effect as a result of eddy current loss, and these possess a large relative magnetic permeability even at levels of a few hundred MHz or more. According to the thin film manufacturing method and apparatus, it is possible to easily manufacture an electromagnetic noise absorbing material having small hysteresis, possessing a hard axis of uni-axial magnetic anisotropy, which is superior in high-frequency response, and has a large electromagnetic noise suppression effect.

A study of occurrence rates of Electromagnetic Interference (EMI) to aircraft with a focus on HIRF (external) High Intensity Radiated Fields

Abstract: This report presents the methodology and results of a subjective study done by Polytechnic University to investigate Electromagnetic Interference (EMI) events on aircraft. The results cover various types of EMI from on-board aircraft systems, passenger carry-on devices, and externally generated disturbances. The focus of the study, however, was on externally generated EMI, termed High Intensity Radiated Fields (HIRF), from radars, radio and television transmitters, and other man-made emitters of electromagnetic energy. The study methodology used an anonymous questionnaire distributed to experts to gather the data. This method is known as the Delphi or Consensus Estimation technique. The questionnaire was sent to an expert population of 230 and there were 57 respondents. Details of the questionnaire, a few anecdotes, and the statistical results of the study are presented.

A deterministic approach to the modelling of electromagnetic wave propagation in urban environments

Abstract: This thesis treats the development of a deterministic model for the electromagnetic (EM) field-strength prediction in built-up areas. The model uses Geometrical Opties (GO) together wi th various diffraction contributions based on the Uniform Theory of Diffraction (UTD) to determine the interaction of the EM wave with the environmental objects. Two applications of the model are discussed in this dissertation. The first one concerns the determination of the effeetiveness of placing an obstacle on the propagation path of an interfering signal in order to raise the signa.l-to-interference ratio of an earth-space link. Results of this intentional signal obstruction are presented for various obstacle types and positions of the observation point. Attention is also paid to the case where a receiving antenna is vcry close to the obstacle. In that case, a separate far-field treatment of obstacle and antenna diffraction is no longer allowed and a combined analysis should be carried out. This near-field analysis is performed for two types of parabolic reflector antennas, and results for the shielding effectiveness of obstacles are presented and compared. Also the validity of applying spatial far-field antenna weighting functions in field-strength prediction models based on ray methods is discussed. The second application of the model described in this thesis is the prediction of the EM field strength of a Land Mobile Satellite (LMS) signal in an urban environment. Due to its deterministic character the model developed is capable of analysing effects such as specular refiection and st rong shadowing. The lat ter are not taken into account in conventional statistical LMS field-strength prediction modeIs. Because the GO j UTD model accepts a detailed description of the urban environment, it can be used to analyse an arbitrary environment, whereas conventiona.l statistical models a.re suited for one specific geometry only. To demonstrate the capability of the model, it was used for the determination of the field strength along two trajectories at the campus of Eindhoven University of Technology. Not only the field strength, but also the Doppier spectrum, the time-delay profile and the delay-Doppler spectrogram were derived. The deterministic model is expeded to be a. valuable complement to existing statistical LMS field-strength prediction modeIs, especially if detailed digital databases of towns and cities are available.

Power-transmission electromagnetics

Abstract: Many issues related to electromagnetic analysis of power lines have been raised. These include some related to the operation of power lines, and others related to effects of the power-line electromagnetic environment. Concern about the latter has been responsible for a renewed interest by the media. An overview of these issues is given. When appropriate, the topics are placed in the context of methods commonly used by those trained in the electromagnetics of antennas and propagation. >

Compatibility relations and the finite-element formulation of electromagnetic field problems

Abstract: When computing an electromagnetic field using the finite element method it is possible that, although Maxwell's equations are discretized accurately, highly inaccurate computational results are obtained. In those cases it can easily be shown that (some of) the electromagnetic compatibility relations (field properties that follow from Maxwell's equations) are not satisfied. The divergence condition on the fluxes, for instance, follows directly from the field equations but not necessarily from their discretized counterparts. This necessitates inclusion of the compatibility relations in the finite-element formulation of the field problem. A survey is given of all electromagnetic compatibility relations. >

Improved wire modelling in TLM

Abstract: An important aspect in the application of transmission-line modelling (TLM) to microwave circuit and electromagnetic compatibility (EMC) simulation studies is the accurate modelling of wires and wire-like structures. This paper outlines the cause of errors arising from simplified descriptions often used when modelling wires by integrated solution methods in TLM. It proposes a simple solution which is validated against experimental results for a number of test configurations. >

Signal to noise transformation, the key to EMC

Abstract: The coupling of electromagnetic fields into or out of electric circuits is described. This coupling is described by means of a signal-to-noise-transformation (SNT), which gives the transformation of a wanted signal to unwanted noise. By using the SNT simple quantitative design rules can be developed which can be used to prevent EMC problems and are helpful in getting more insight into coupling phenomena. >

Photonic systems for antenna applications

Abstract: For well over a decade, research groups around the world have been investigating photonic devices for use in antenna, phased array, and electromagnetic field sensor systems. Applications have included shipboard EMC monitoring, EMP measurements, anechoic chamber calibration, novel antenna and array designs, antenna remoting, and smart skins. Photonic antenna links allow immunity from electromagnetic interference, provide an extremely wide working bandwidth, and allow long cable runs with a minimum of loss. Recent developments in laser technology allow photonic-based links to have very low noise figure and high dynamic range. Optoelectronic devices are now being built in III-V semiconductors (GaAs, InP) and polymers which will ultimately lead to opto-electronic integration with MMIC devices. Photonic systems will revolutionize the way in which electromagnetic measurement and antenna systems will be designed and built in the future. This paper presents an overview to the different types of photonic links and modulator systems available to the antenna engineer. >

Inductive noise cancellation circuit for electromagnetic pickups

Abstract: A cancellation circuit provides active electromagnetic shielding for canceling inductive noise in electrical circuits caused by electromagnetic flux. The cancellation circuit includes amplitude-adjustment and phase-adjustment circuits for adjusting the amplitude and phase of electrical signals, and a combining circuit for combining electrical signals such that the effects of electromagnetic induction cancel. An electromagnetic pickup is provided with a cancellation circuit for canceling its response to electromagnetic flux. An electromagnetic drive coil is provided with a cancellation circuit for canceling electromagnetic flux in a predetermined region of space, and a compensation circuit compensates for frequency-dependent phase and amplitude variations in electrical pickup signals and transmitted electromagnetic flux. The cancellation and compensation circuits may be combined to provide a device that can simultaneously transmit and receive electromagnetic radiation.

Comparison of time domain and frequency domain electromagnetic susceptibility testing

Abstract: Electromagnetic susceptibility testing in the frequency domain requires a lot of test equipment and much time for the examination in a wide frequency range, from a few kHz to several hundreds of MHz. Frequency steps must be small enough to allow the indication of resonance frequencies. Fourier transformation shows the correlation between time domain and frequency domain. By this transformation, results of susceptibility tests with nanosecond impulses can be analyzed in the frequency domain. Frequency responses of simple devices under test are calculated from the results of impulse testing in the time domain. They show the same characteristics as the results of frequency domain tests. The impulse test method seems to be a simple and fast tool to find the weak points of electric systems against electromagnetic radiation. Because of their importance for susceptibility of electronic circuits, investigations on cables and conductors on printed-circuit boards (PCB) are put forward. Further on, the presented comparison of time domain and frequency domain test methods can be taken into account for emission measurements of electronic equipment measured with ordinary TEM (or GTEM) cells in the time domain. >

Code division multiple access for an automotive area network over power-lines

Abstract: This article presents a particular application of the spread spectrum code division multiple access concept (CDMA) based on direct spread spectrum modulation (DS-SSM) for an automotive area network on power-lines. Advantages and related problems to set up the system in a car are discussed. Measurements for the evaluation of the system's performances in terms of the additive noise and the interference caused by the other users are given. Design of this communication system is made taking also into account protection against electromagnetic disturbances. >

Expert system measures harmonics and EMC

Abstract: The effects of power system harmonics are becoming more and more important as the number of rectifier controlled motors, discharge lamps, and television equipment grows in industrial and utility power systems.The author describes how a modular expert system for measurement and analysis of power system harmonics and electromagnetic compatibility was developed. The system is capable of sampling up to eight channels (either voltage or current) with a sampling frequency of 30 kHz. The measured and digitized values are stored on a hard disk. Discrete Fourier transformation (DFT) analysis may be carried out online for preliminary evaluation and display of the harmonics. This modular, PC-based system may be applied to a variety of industrial and utility electric system analysis tasks, and also used in education. >

Analysis of Electromagnetic Compatibility Between Radar Stations and 4 GHz Fixed-Satellite Earth Stations

Abstract: The susceptibility of 3700– to 4200–MHz fixed–satellite service earth stations to interference from radar signals, and the mechanisms by which such interference can occur, are examined. It is shown that interference can occur even if all currently applicable NTIA and FCC spectrum engineering requirements for radar emissions and earth station receiver systems are satisfied. It is further shown that while most interference problems can be resolved by installing appropriate radio frequency (RF) filtering on either the radar transmitter RF output or the earth station RF input, determination of the system that requires filtering depends critically upon the interference coupling mechanism. Methods for determining the interference coupling mechanism are presented.

Test apparatus for testing the susceptibility of electronic equipment to electromagnetic radiation and for measuring electromagnetic radiation emitted by electronic equipment

Abstract: EMC test apparatus for EMC testing electronic equipment comprises an electromagnetic screening enclosure for receiving the electronic equipment and a stripline antenna suspended within the enclosure and extending thereacross. The stripline antenna has a width less than half the wavelength of the highest frequency of the electromagnetic radiation at which EMC testing is to take place. Electrical connectors are provided through the enclosure to allow the connection of EMC test equipment to the stripline antenna.

Crosstalk on printed circuit boards

Abstract: This document treats the crosstalk between parallel conductors. The conductors can represent either conductors in a multiconductor cable or traces on a printed circuit board (PCB). An analysis method based on a lumped circuit equivalent for the problem as well as a method to calculate the per unit length parameters are presented. The computed results are validated by comparison with measurements as well as an exact solution of the multiconductor transmission line equations. Several PCB-layouts are analysed to demonstrate how the crosstalk on a PCB can be minimised.

Using GTEM for electromagnetic emission measurements: experiments in test result correlation

Abstract: Electromagnetic emissions from a digital broadband source were measured in 30-1000 MHz frequency band using different EMC test facilities: GigaHertz transverse electromagnetic field cell (GTEM), two open area test sites (OATS), and a 3 m site-size RF absorber lined room (AR). While the mean values of the variance between the respective data obtained at these facilities were around 6 dB, the difference between the individual readings could exceed 11-15 dB, confirming the limited character of correlation. On the other hand, the disparities between the GTEM measurement results versus OATS and AR, were of a similar order comparing to those between the OATS and AR, or even between different OATS. Several reasons for these disparities are investigated, including inherent specifics of the facilities, EUT positioning, and cable manipulations. >

EMC in power electronic devices: radiated emissions from a silicon controlled rectifier

Abstract: During the last decade, great achievements in the field of power electronics have significantly contributed to its promotion in all areas of engineering. However, its evolution to an indispensable factor in today's industrial applications has also involved a certain number of problems which have not yet been studied thoroughly or completely solved. For instance, the electromagnetic interference emanating from power converters in particular frequency ranges. The aim or this paper is to identify the main sources of radiated noise emission from a silicon controlled rectifier (SCR) by means of the correlation between common mode currents and electromagnetic field measurements. Moreover, an equivalent radiation model is to be developed enabling emission level prediction in the design phase when compliance of the device with international standard regulations is to be verified. Direct measurements of common mode current spectra and the E-field emanating from a SCR bridge allow the correlation between them to be found, thus identifying the origin of the radiation. Both time domain waveforms and the corresponding spectra are monitored for several operation points at different locations on the set-up. Field measurements are also carried out for each operating point for vertical and horizontal polarization. The study has yielded a number of interesting results concerning the identification of the main common mode current propagation paths and their radiating effects. >

Prediction of transient electromagnetic environment in power networks

Abstract: In this paper the authors suggest exact analytic formulations which allow numerical characterization of the transient electromagnetic environment, during operation of circuit breakers or disconnecters, of an electric power transmission network. In this work, an exact method for calculating the transient field radiated by an air insulation substation (AIS) together with the strictest formalism which enables the same calculation to be made for a power transmission line are paid particular attention. Results of simulations for different examples together with results of measurements complete the study. >

IC design considerations for the harsh automotive electrical environment

Abstract: This paper provides the reader with an overview of automotive industry standards for electromagnetic compatibility (EMC), electrostatic discharge (ESD) and the thermal environment. Integrated circuit designers who work on automotive products must be technically aware of the harsh electrical environment that their ICs must not only survive, but often operate within specification. The many sources of electromagnetic interference (EMI) and its negative impact on electrical system performance are examined. More importantly to the IC designer, the design techniques for improving EMC and reducing EMI at the IC level are presented. >

Robust methods for EMC-driven routing

Abstract: Due to the application of fast device technologies and the increasing complexity of printed-circuit boards, electromagnetic phenomena, e.g. reflections and crosstalk, gain more and more importance and may even disturb the function of a circuit. In the future, it will be indispensable to already consider phenomena of electromagnetic compatibility (EMC) during layout synthesis. In this paper, robust methods are presented that make it possible for the first time to incorporate complex EMC constraints and cost criteria into printed-circuit board routing. This includes both concepts for the development and specification of EMC design models and robust and efficient algorithms for EMC-driven routing that can handle these models. >

Recent test results of 6 commercial inverters for grid connected PV systems

Abstract: Test results of 6 commercial inverters for grid connected PV systems in the power range up to 5 kW are given. The considered aspects include: energy efficiency, power point tracking efficiency, start-up power, power quality, conformity to EMC standards, acoustic noise and susceptibility to electromagnetic noise. The results are obtained with the PV test facility of ECN. The results show that in the last few years considerable progress has been made concerning the performance of grid connected inverters which are available on the European market. In general the efficiency is over 88% over a wide power range, with a peak efficiency of about 92%. Most inverters comply with standards concerning power factor, harmonics, EMC and acoustic noise.