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Note of Electromagnetic Interference And Compatibility by Akash Sharma

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Fatima Michael College of Engineering & Technology DEPARTMENT OF ELECTRONICS AND COMMUNIUCATION ENGG EC6011 ELECTROMAGNETIC INTERFERENCE AND COMPATIBILITY Regulation: 2013 Final year odd semester 1 Fatima Michael College of Engineering & Technology

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Fatima Michael College of Engineering & Technology SYLLABUS EC6011 ELECTROMAGNETIC INTERFERENCE AND COMPATIBILITY L T PC 3 003 UNIT I BASIC THEORY 8 Introduction to EMI and EMC, Intra and inter system EMI, Elements of Interference, Sources andVictims of EMI, Conducted and Radiated EMI emission and susceptibility, Case Histories, Radiationhazards to humans, Various issues of EMC, EMC Testing categories, EMC Engineering Application. UNIT II COUPLING MECHANISM 9 Electromagnetic field sources and Coupling paths, Coupling via the supply network, Common mode coupling, Differential mode coupling, Impedance coupling, Inductive and Capacitive coupling,Radiative coupling, Ground loop coupling, Cable related emissions and coupling, Transient sources, Automotive transients. UNIT III EMI MITIGATION TECHNIQUES 10 Working principle of Shielding and Murphy‘s Law, LF Magnetic shielding, Apertures and shielding effectiveness, Choice of Materials for H, E, and free space fields, Gasketting and sealing, PCB Level shielding, Principle of Grounding, Isolated grounds, Grounding strategies for Large systems, Grounding for mixed signal systems, Filter types and operation, Surge protection devices, Transientprotection. UNIT IV STANDARDS AND REGULATION 9 Need for Standards, Generic/General Standards for Residential and Industrial environment, Basic Standards, Product Standards, National and International EMI Standardizing Organizations; IEC,ANSI, FCC, AS/NZS, CISPR, BSI, CENELEC, ACEC. Electro Magnetic Emission and susceptibility standards and specifications, MIL461E Standards. UNIT V EMI TEST METHODS AND INSTRUMENTATION 9 Fundamental considerations, EMI Shielding effectiveness tests, Open field test, TEM cell for immunity test, Shielded chamber , Shielded anechoic chamber, EMI test receivers, Spectrum analyzer, EMI test wave simulators, EMI coupling networks, Line impedance stabilization networks,Feed through capacitors, Antennas, Current probes, MIL -STD test methods, Civilian STD testmethods. TOTAL: 45 PERIODS TEXT BOOK: 1. Clayton Paul, ―Introduction to Electromagnetic Compatibility‖, Wiley Interscience, 2006 REFERENCES: 1. V Prasad Kodali, ―Engineering Electromagnetic Compatibility‖, IEEE Press, Newyork, 2001. 2. Henry W. Ott, ―Electromagnetic Compatibility Engineering‖, John Wiley & Sons Inc, Newyork, 2009 3. Daryl Gerke and William Kimmel, ―EDN‘s Designer‘s Guide to Electromagnetic Compatibility‖, Elsevier Science & Technology Books, 2002 4. W Scott Bennett, ―Control and Measurement of Unintentional Electromagnetic Radiation‖, John Wiley & Sons Inc., (Wiley Interscience Series) 1997. 5. Dr Kenneth L Kaiser, ―The Electromagnetic Compatibility Handbook‖, CRC Press 2005 Fatima Michael College of Engineering & Technology

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Fatima Michael College of Engineering & Technology UNIT I Basic Theroy INTRODUCTION TO ELECTROMAGNETIC COMPATIBILITY (EMC) Since the early days of radio and telegraph communications, it has been known that a spark gap generates electromagnetic waves rich in spectral content (frequency components) and that these waves can cause interference or noise in various electronic and electrical devices such as radio receivers and telephone communications. Numerous other sources of electromagnetic emissions such as lightning, relays, dc electric motors, and fluorescent lights also generate electromagnetic waves that are rich in spectral content and can cause interference in those devices. There are also sources of electromagnetic emissions that contain only a narrow band of frequencies. High-voltage power transmission lines generate electromagnetic emissions at the power frequency [60 Hz; 50 Hz in Europe]. Radio transmitters transmit desired emissions by encoding information (voice, music, etc.) on a carrier frequency. Radio receivers intercept these electromagnetic waves, amplify them, and extract the information that is encoded in the wave. Radar transmitters also transmit pulses of a single-frequency carrier. As this carrier frequency is pulsed on and off, these pulses radiate outward from the antenna, strike a target, and return to the radar antenna. The total transit time of the wave is directly related to the distance of the target from the radar antenna. The spectral content of this radar pulse is distributed over a larger band of frequencies around the carrier than are radio transmissions. Another important and increasingly significant source of electromagnetic emissions is associated with digital computers in particular and digital electronic devices in general. These digital devices utilize pulses to signify a binary number, 0 (off) or 1 (on). Numbers and other symbols are represented as sequences of these binary digits. The transition time of the pulse from off to on and vice versa is perhaps the most important factor in determining the spectral content of the pulse. Fast (short) transition times generate a wider range of frequencies than do slower (longer) transition times. The spectral content of digital devices generally occupies a wide range of frequencies and can also cause interference in electrical and electronic devices. This text is concerned with the ability of these types of electromagnetic emissions to cause interference in electrical and electronic devices. The reader has no doubt experienced noise produced in an AM radio by nearby lightning discharges. The lightning discharge is rich in frequency components, some of which pass through the input filter of the radio, causing noise to be superimposed on the desired signal. Also, even though a radio may not be tuned to a particular transmitter frequency, the transmission may be received, causing the reception of an unintended signal. These are examples of interference produced in intentional receivers. Of equal importance is the interference produced in unintentional receivers. For example, a strong transmission from an FM radio station or TV station may be picked up by a digital computer, causing the computer to interpret it as data or a control signal resulting in incorrect function of the computer. Conversely, a digital computer may create emissions that couple into a TV, causing interference. This text is also concerned with the design of electronic systems such that interference from or to that system will be minimized. The emphasis will be on digital electronic systems. An electronic system that is able to function compatibly with other electronic systems and not produce or be susceptible to interference is said to be electromagnetically compatible with its environment. The objective of this text is to learn how to design electronic systems for electromagnetic compatibility (EMC). A system is electromagnetically compatible with its environment if it satisfies three criteria: Fatima Michael College of Engineering & Technology

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Fatima Michael College of Engineering & Technology 1. It does not cause interference with other systems. 2. It is not susceptible to emissions from other systems. 3. It does not cause interference with itself. Designing for EMC is not only important for the desired functional performance; the device must also meet legal requirements in virtually all countries of the world before it can be sold. Designing an electronic product to perform a new and exciting function is a waste of effort if it cannot be placed on the market! EMC design techniques and methodology have become as integral a part of design as, for example, digital design. Consequently the material in this text has become a fundamental part of an electrical engineer‘s background. This will no doubt increase in importance as the trend toward increased clock speeds and data rates of digital systems continues. The most important aspect in successfully dealing with EMC design is to have a sound understanding of the basic principles of electrical engineering (circuit analysis, electronics, signals, electromagnetics, linear system theory, digital system design, etc.). We will therefore review these basics so that the fundamentals will be understood and can be used effectively and correctly by the reader in solving the EMC problem. ASPECTS OF EMC As illustrated above, EMC is concerned with the generation, transmission, and reception of electromagnetic energy. These three aspects of the EMC problem form the basic framework of any EMC design. This is illustrated in Fig. 1.1. A source (also referred to as an emitter) produces the emission, and a transfer or coup- ling path transfers the emission energy to a receptor (receiver), where it is processed, resulting in either desired or undesired behavior. Interference occurs if the received energy causes the receptor to behave in an undesired manner. Transfer of electromagnetic energy occurs frequently via unintended coupling modes. However, the unintentional transfer of energy causes interference only if the received energy is of sufficient magnitude and/or spectral content at the receptor input to cause the receptor to behave in an undesired fashion. Unintentional trans- mission or reception of electromagnetic energy is not necessarily detrimental; unde- sired behavior of the receptor constitutes interference. So the processing of the received energy by the receptor is an important part of the question of whether interference will occur. Quite often it is difficult to determine, a priori, whether a signal that is incident on a receptor will cause interference in that receptor. For example, clutter on a radar scope may cause a novice radar operator to incorrectly interpret the desired data, whereas the clutter may not create problems for an operator who has considerable experience. In one case we have interference and in the other we do not, although one could argue that the receptor is the radar operator and not the radar receiver. This points out that it is often difficult to uniquely identify the three aspects of the problem shown in Fig. 1.1. FIGURE 1.1 The basic decomposition of the EMC coupling problem. It is also important to understand that a source or receptor may be classified as intended or unintended. In fact, a source or receptor may behave in both modes. Whether the source or the receptor is intended or unintended depends on the coup- ling path as well as the type of source or receptor. As an example, an AM radio station transmitter whose transmission is picked up by a radio receiver that is tuned to that carrier frequency constitutes an intended emitter. On the other hand, if the same AM radio transmission is processed by another radio receiver that is not tuned to the carrier frequency of the transmitter, then the emission is unintended. (Actually the emission is still intended but the coupling path is not.) There are some emitters whose emissions can serve no useful purpose. An example is the (nonvisible) electromagnetic emission from a fluorescent light. Fatima Michael College of Engineering & Technology

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