Fundamentals of Applied EMC (electromagnetic compatibility)--Introduction

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Over the past three decades the electromagnetic compatibility (EMC) considerations in the design of digital electronic devices or components have grown in importance throughout the world. This is because the United States and other industrial nations don’t allow electronic devices to be marketed in their countries unless their electromagnetic noise emissions have been tested and certified to meet certain limits. As a result the electronic industries are showing increasing interest in electrical engineering (EE) graduates with an EMC background. Currently, except for a handful of schools, the undergraduate EE programs in the United States don’t address the EMC issues directly, although most of them require at least one 3- or 4-credit course in electromagnetics.

Students specializing in fields and waves are probably equipped to investigate certain fundamental problems of EMC. A few well-known schools with strong programs in electromagnetics often express the opinion that a good training in fields and waves prepares the students sufficiently to meet the challenges of EMC in their professional life. Nevertheless, to meet the growing demand from industries, the IEEE is actively encouraging schools to include EMC as a course topic in their curricula.

During the Fall of 2005 we introduced a senior/graduate level course in EMC: at the Electrical Engineering and Physics Department at our local University. It was taken mostly by practicing engineers from automobile-manufacturing and other related industries. Our own attending EE students had varied levels of background in electromagnetics but none had the expected familiarity with Maxwell's equations and plane electromagnetic waves. Because of this we faced difficulties in the planning of the course. In addition at that time we had a very limited selection of textbooks on EMC. We chose Introduction to Electromagnetic Compatibility by C. R. Paul supplemented by Noise Reduction Techniques in Electronic Systems by H. R. Ott, but found them not completely suitable for our students' needs. It was therefore necessary to develop lecture notes specialized to the class. The initial lectures were devoted to bringing the students' background level in electromagnetics up to a uniform level of familiarity with Maxwell's equations. After this, plane waves and related topics, transmission lines, antennas, and radiation were introduced. Overall, knowledge of these topics was deemed to be a necessary minimum background for an EMC course. The rest of the lectures were on selected topics in EMC. The course was so well received that it was repeated the next year (2006). Because of continued demand it’s still being offered every alternate year.

Our experience motivated us to write a textbook combining the fundamentals of fields and waves, a few selected topics of applied electromagnetics, and a variety of topics typical of EMC. The descriptions of electromagnetics are placed in the context of EMC, and those of EMC are presented where they help in the analysis of EMC phenomena as well as in planning the measurements needed for compliance with EMC specifications. The guide is also an outgrowth of classroom lecture notes for a number of undergraduate/graduate level courses in electromagnetic theory and applied electromagnetics given by the first author over many years at the electrical engineering departments.

A brief outline of the guide follows. Section 1 introduces electromagnetic interference in general, and describes the evolution of EMC in the digital electronics era. It also defines various acronyms that are used alternatively, and often erroneously, to describe interference effects. The electromagnetic environment consists of a variety of natural and human-made noise sources in which electronic devices are expected to operate. These noise sources are described in Section 2. Section 3 is about the fundamental concepts and relations of electromagnetic fields and waves. Basic laws of electricity and magnetism, their generalizations, and their mathematical descriptions by Maxwell are described. Boundary conditions, the Poynting theorem, and energy transfer are then discussed. The time harmonic formulation of Maxwell's equations are introduced next and their applications to general problems are described. Finally, uniform plane waves in lossless and lossy media, skin effect phenomena, and reflection and refraction of plane waves are discussed. Section 4 describes the frequency spectra of known electromagnetic sources to the extent necessary for the characterization of their electromagnetic emissions as functions of frequency from the viewpoint of EMC. Basic characteristics and applications of TEM transmission lines and, in particular, the two-wire, coaxial, microstrip, stripline, and parallel plate lines are briefly described in Section 5. The time dependent or the transient solutions for a two-wire line are also briefly mentioned here. Section 6 discusses the fundamentals of antennas and radiation, including the equivalent circuits for receiving and transmitting antennas. The radiation from basic antennas, such as the electric and magnetic dipoles, is described in detail; these descriptions are then utilized in the discussion of certain general characteristics of radiation. In addition the half-wave dipole and the biconical antenna are described.

The behavior of the lumped circuit parameters R, L and C are described in Section 7. The field theory definitions of these parameters are introduced at first; they are then used to analyze performance as functions of frequency.

Section 8 gives analytical descriptions of the radiated emissions from certain components of an electronic device and their susceptibility to outside noise. Simple wire and transmission-line models are used to estimate these emissions and susceptibility of the components when illuminated by incident plane waves from outside sources. Principles of electromagnetic shielding are briefly described in Section 9. The inductive and capacitive coupling effects in selected circuit configurations are outlined in Section 10. Section 11 deals with the electrostatic discharge (ESD) phenomenon and its impact on the design of electronic systems from the viewpoint of EMC. Section 12 gives the typical standards for EMC prescribed by the FCC for both Class A and Class B types of electronic devices. Some European standards are also mentioned. Section 13 describes briefly the measurement procedures that are followed to test the compliance of a device to the emission limits required by the enforcing agency. Appendix A gives a rather complete description of the vectors and vector calculus that are essential background knowledge for any course in electromagnetics. Problems, and answers to many of them, are provided at the end of some sections.

The guide is intended to serve as a textbook for courses on applied electromagnetics and electromagnetic compatibility at the senior/graduate level in EE. The prerequisites for such a course are completion of basic undergraduate EE and physics courses in electricity and magnetism, analog and digital electronic circuits, and advanced calculus.

The description of fields and waves starts at the basic level and then proceeds to a fairly high level. Topics in EMC are described such that the electromagnetic interference effects associated with them can be better understood.

Depending on the electromagnetic background of the class, the instructor may apply higher discretion to adjust the emphasis on specific course materials.

For a class with a sufficient background in electromagnetic fields, the guide can be used by the instructor to delve into the discussed EMC topics in more detail and also to put forward additional EMC topics. For example, one could include designs for EMC that are not considered here and extend the discussion of EMC measurements. The appropriate materials for taking this direction are in Sections 1, 2, and 7 through 13.

This guide is also designed to serve as a textbook for coursework on applied electromagnetics. The appropriate sections are 3 through 6 (and perhaps 7) and Appendix A. The instructor may choose to include more discussion of these topics as well as more materials on antennas, for example. Such a course might even be followed by the course on EMC described earlier.

Finally, practicing engineers in industry interested in exploring EMC may find the guide useful for self-study. The topics and descriptions are such that engineers involved in the design of electronic devices for EMC will find the guide useful as a reference tool.

  1. General Considerations
  2. The Electromagnetic Environment
  3. Fundamentals of Fields and Waves
  4. Signal Waveform and Spectral Analysis
  5. Transmission Lines
  6. Antennas and Radiation
  7. Behavior of Circuit Components
  8. Radiated Emissions and Susceptibility
  9. Electromagnetic Shielding
  10. Coupling between Devices
  11. Electrostatic Discharge (ESD)
  12. EMC Standards
  13. Measurements of Emission

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