latha mathavan engineering college kidaripatti, madurai … sem.pdf · electromagnetic interference...

LATHA MATHAVAN ENGINEERING COLLEGE

Kidaripatti, Madurai – 625301

Subject: EC6011 Electro Magnetic Interference & Compatibility Year &Semester: IV year ECE / VII SEM

Faculty: Mr.M.ANANDAN, ASP/ECE Question Bank & University Questions with Answer

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UNIT 1 BASIC THEORY Question Bank PART – A

1. Why is EMC a vital problem? Define LISN. Nov2016

2. List the testing strategies in EMC. EC6011May 2017

3. What are the three criteria to be satisfied by any system to become electromagnetically compatible?

4. With suitable diagrams, give one example for (i) conducted type EMI and (ii) radiated type EMI.May2014

5. What is meant by electromagnetic compatibility?

6. Why do we feel electric shock at times, when we touch TV and Computer monitors?

7. List the sources of EMI.

8. Define ESD.

9. Draw an equivalent circuit model for electrostatic discharge.

10. Define Radiated Emission. PART – B

1. (i) Distinguish between the features of conducted EMI and radiated EMI. (8) EC6011May 2017

(ii) Explain the different sources of EMI in detail. Give examples. (8) EC6011May 2017

2. Discriminate time domain and frequency domain EMI. Why analysis does is made in frequency approach

Analysis, design and location of high voltage equipment. (16) EC6011May 2017

3. (i) What are the sources and victims of EMI? Explain with examples.

(ii) Explain in detail classification of EMI/EMC. How do you minimize each?

4. (i) Compare time domain EMI with frequency domain EMI.

(ii) Explain ESD in detail. What are all the remedial procedures?

5. (i) Why is EMI significant in system design? Explain with industry citations. What are the sources and

Victim of EMI?

(ii) How do electrostatic discharges occur? Explain in detail EMI radiation Hazards.

6. How are the various sources of EMI kept under control and measured? What are the various

Parameters of measurement? Give their relevant units.

UNIT II COUPLING MECHANISM PART – A

1. What is transient coupling? EC6011May 2017

2. Define LISN. EC6011May 2017

3. Define edge rate. Define Transient Coupling.

4. List out the types of coupling between cables

5. Define cross talk with reference to EMI/EMC design issues?

6. Define ‘Ground’ with respect to working on electrical gadgets.

7. Define Ground coupled Interference.

8. How does one avoid power mains interference?

9. Why is a limit on the lower frequency portion ofthe conducted emission and which is the standard

Followed during the testing accordingly?

10. What are the steps in the procedure to analyze EMP susceptibility? PART – B

1. (i)Describe the differences between radiated DM and CM coupling with suitable example.

(ii) With neat diagram explain near field coupling.

2. Discuss in detail with neat diagram about ground loop coupling and power supply coupling.(or) Explain in

Detail various coupling methods/mechanisms.

3. Explain in detail the conducted, radiated and common impedance ground couplings with examples.

4. What is radiated differential mode coupling? In what way this is different from the radiated

Common mode coupling? Explain this with example.

5. Explain cable coupling and its electromagnetic impact in system design.

UNITIII EMI MITIGATION TECHNIQUES PART – A

1. Formulate the shielding effectiveness of E and H fields. EC6011May 2017

2. What is meant by ‘bulging’ capacitor? EC6011May 2017





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3. What are the advantages of multipoint grounding?

4. What is the functionality of transient suppressors?

5. Classify EMI filters.

6. What is EMI shielding? What is the need for shielding?

7. Name four techniques/approaches to combat EMI.

8. What does ‘Chemical Salting’ mean?

9. What is an electrical filter?

10. Write the definitions of grounding and bonding. PART – B

1. (i) How does an isolation transformer control EMI? Explain shielding and filtering methods of controlling EMI.(8)

(ii) Explain various method of grounding with examples. (8) EC6011May 2017

2.(i) How does cable routing control EMI ? How signal control is is achieved? (8) EC6011May 2017

(ii) Describe the shielding effectiveness of both solid and non-solid materials including multiple soil shields

and thin film shielding. (8) EC6011May 2017

2. What ate the factors influencing the EMI performances of the bonding? How can bonding be made?

Mention some guidelines for good bonds.

3. (i) What are Isolation Transformers? Explain in detail.

(ii) Explain various method of grounding with examples.

4. (i)What are transient suppressors? Explain them.

(ii)Explain briefly the cable routing and signal control techniques.

5. Explain different shielding techniques .

UNIT IV STANDARDS AND REGULATION PART– A

1. Analyze the key for Conducted Emission (CE) EMC standards. EC6011May 2017

2. Interpret the need for EMI standards. EC6011May 2017

3. Why do CISPR standards evolve?

4. Can High Voltage lines be allowed to cross residential sites? Justify.

5. How test bed is selected for ESD testing?

6. What are CISPR standards for EMIC?

7. What are Class A devices with reference to FCC?

8. What are MIL STD 461,462 and 463?

9. Name at least two standards for design guidelines and Test and Measurement procedures published by IEEE/ANSI.

10. What is the objective of requirements CS 103/104/105? PART – B

1. Summarize FCC and CISPR Conducted Emission and Radiated Emission standards.(16) EC6011May 2017

2. Write short notes on (i) BSI (8) (ii) CENLEC.(8) EC6011May 2017

3. (i) What is the need for EMI standards? Explain.

(ii) Explain the civilian standards FCC, CISPR and IEC in detail.

(iii) Mention the requirements for the EMI shielded chamber.

4. (i)Write in detail about the specifications of Electromagnetic emission and susceptibility.

(ii) What are the needs for civilian &military standards? Compare & contrast with IEC and MIL461E462 standards.

5. (i)Discuss, in detail, the role of ANSI standards in EMI/EMC area. (8) EC9029 Nov2012

(ii)Why are military standards more stringent for Radiated Emission? (8) EC9029 Nov2012

6. Why do the standards vary with reference to civilian and military applications? What are the

Various standards for civilian applications? How do they evolve? Discuss them in detail.

7. Tabulate conducted and radiated emission limits under military standards and explain.

UNIT V EMI TEST METHODS AND INSTRUMENTATION PART – A

1. Give the list of antenna used for microwave frequencies. EC6011May 2017

2. What is the significance of narrow band test? EC6011May 2017

3. What is the main difference between radiated measurements for class A devices and others?

4. Write the objective of CS measurement. EC9029 Nov2012

5. List the applications of EMI test receiver. EC9029 Nov2012





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6. Mention the two very important needs for TEM cell. With neat diagrams explain TEM cell.

7. How test bed is selected for ESD testing?

8. What are the advantages of loop antenna?

9. Define the term LISN? With LISN draw the basic circuit used for RI measurements?

10. What is a current probe? Give some guidelines to carry OATS. PART – B

1. Describe about the Open area test site measurements, What are its limitations? outline the characteristics

of open area test site. (16) . EC6011May 2017

2. (i) Formulate the various EMI test instruments. (8) EC6011May 2017

(ii) Develop a test bed for EFT. (8) EC6011May 2017

3. (i)With circuit diagram explain the working principle of feed through capacitor.(8) EC9029 Nov2012

(ii)Derive the expression for NSA of OATS.(8) EC9029 Nov2012

4. How are measurements made in the following: (i) Tx/Rx Antennas (ii) EMI Rx and spectrum analyzer

5. Explain the step-by-step approach for evaluating RE and RS using TEM cell

6. (i)Discuss how LISN is placed in a measurement set-up.

(ii) Why do the standards vary with reference to civilian and military applications? What are the

various standards for civilian applications? How do they evolve? Discuss them in detail.

7. (i) Explain various testing antenna and their frequencies as specified in CISPR standard.

(ii) What is TEM cell? Explain in detail with neat diagram.

EC6011 Electro Magnetic Interference &Compatibility Questions with Answers

Unit 1 Part –A

1. Define EMI

Electromagnetic interference is the degradation in the performance of a device, or equipment, or a

System caused by an electromagnetic disturbance.

2. Define EMC

The ability of a receptor (a device, or equipment, or a system) to function satisfactorily in its Electromagnetic

environment without at the same time introducing intolerable electromagnetic disturbances to any other

device/equipment/system in that environment is called electromagnetic Compatibility.

3. What are the three criteria for an electromagnetically compatible system to satisfy?

An electromagnetically compatible system satisfies three criteria are 1. It does not interfere with the operations of

other systems. 2. It is immune from the emissions of other systems. 3. It does not interfere with its own operation

4. What are the different EMI Sources in Circuits?

Local oscillators Switches Motors Filters Relays Circuit breakersLogic & Digital circuits

5. What are the three ways to prevent interference? There are three ways to prevent interference: 1.Suppress the emission at its source. 2. Make the coupling

path as inefficient as possible. 3. Make the receptor less susceptible to the emission.

6. What are the various methods to eliminate EMI?

The effective methods to eliminate EMI are: Shielding, Grounding, Bonding, Filtering, Isolation,

Separation and orientation, Cable design.

7. What are the major elements of electromagnetic?

Source (also as an emitter) produces the emission. It may be a noisy component, or a transmitter

Receptor (also as a victim) is a component or device that receives noise or interference from the source

Coupling path transfers the emission energy to a receptor, where it is processed, resulting in either desired or

undesired behavior.

8. Write down the mathematical expression for ESD.

A(t) = 1943 (e−t⁄2.2 − e−t⁄2) + 857 (e− t⁄22 − e−t⁄20)

9. What is Electro Static Discharge?

Electrostatic discharge (ESD) is the sudden flow of electricity between two electrically charged objects caused by

contact, an electrical short, or dielectric breakdown. A buildup of static electricity can be caused by charging or by

electrostatic induction.

10. What is electromagnetic pulse (EMP)?

A nuclear explosion results in generation of EMP which is highly intense compared to any natural source.

Nuclear EMP leads to generation of EMI in severe form.





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Part – B

1. Explain about various units of EMI / EMC.

EMI/EMC UNITS: Radiated emissions and radiation susceptibility are measured in terms of field strength (volts per

meter, or tesla). Conducted emissions and conducted susceptibility are measured as Voltages and currents (volts, or

amperes). Single-frequency or very narrowband measurements are expressed as amplitude, whereas broadband

measurements are expressed on a per unit bandwidth (e.g., per Hertz) basis.

Voltage : Volts = 103 millivolts (mV) = 106 microvolts 0V)

dBV = dB above one volt reference level dBmV = dB above one millivolt reference level

dBp.V = dB above one microvolt reference level ,dBV = 20 log10 [(V in volts)/1 volt]

Current: Amps = 103 milliamps (mA) = 10

6 microamps (JJ-A) dBA, dBmA, dBJJ-A

Power : Watts = 103 milliwatts (mW) = 10

6 microwatts (JJ-W) = 10

12 picowatts (pW) dBW, dBmw,dBJJ-W

dEW= 10log10 [(Pin watts)/1 watt] , Electric field : Volts per meter, dBv/meter, dBmv/meter, etc.

Magnetic field (B =μ H) , Tesla = webers/m = 104 Gauss

Source strength of weak celestial source, Flux unit (FU) = -260 dBW/m2/Hz

2.Explain about case history of EMC

During World War II, the use of electronic devices, primarily radios, navigation devices, and radar, accelerated.

Instances of interference between radios and navigational devices on aircraft began to increase. Today, these

interference remedies could be easily implemented on a case-by-case basis in order to correct any electromagnetic

interference (EMI) problem. In 1933 a meeting of the International Electro- technical Commission (IEC) in Paris

recommended the formation of the Inter- national Special Committee on Radio Interference (CISPR) to deal with the

emerging problem of EMI. The committee produced a document detailing measurement equipment for determining

potential EMI emissions.

In 1982 the United Kingdom lost a destroyer, the HMS Sheffield, to an Exocet missile during an engagement with

Argentinian forces in the battle of the Falkland Islands. The destroyer‘s radio system for communicating with the

United Kingdom would not operate properly while the ship‘s antimissile detection system was being operated due to

interference between the two systems. To temporarily prevent interference during a period of communication with the

United Kingdom, the antimissile system was turned off. .Unfortunately, this coincided with the enemy launch of the

Exocet missile.

On July 29, 1967, the U.S. aircraft carrier Forrestal was deployed off the coast of North Vietnam. The carrier deck

contained numerous attack aircraft that were fueled and loaded with 1000-pound (lb) bombs, as well as air-to-air and

air-to-ground missiles. One of the aircraft missiles was inadvertently deployed, striking another aircraft and causing

an explosion of its fuel tanks and the subsequent death of 134 service people. These are a few of the many instances of

EMI in our dense electronic world.

3. Explain the different sources of EMI in detail. Give examples.





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4. Explain in detail about RADIATION HAZARDS TO HUMANS?

EM waves, light, heat, x-ray and gamma rays are all different forms of electromagnetic radiation. However,

they differ in their wavelength. These radiations have hazardous effects on men and material. The effects

can be divided into two categories. 1. Thermal Effects 2. Non-thermal Effects.

1. Thermal Effects: The damaging levels depend on frequency, ambient temperature, body resistance

and weight of individuals exposure over an energy density of 10 mw/cm2 at any frequency is considered

to be not safe.

2. Non-thermal Effects: i) Minor changes in human blood properties take place. ii) Buzzing sound is heard

upon exposure to EMR. iii) Abnormalities of the chromosome structure occurs. iv) Epigastria distress,

emotional upsets and nausea have been noticed.

Radiation limits in the frequency range of 0.1 to 100 GHz when personnel are exposed to EM radiations are

1.The average incident power density should not exceed 10 mw/cm2 for exposures greater than 30

seconds.2.The average incident energy density should not exceed 300 mJ/cm2 for intermittent exposures

between 3 and 30 seconds.3.According to IEEE, safe power density level is 2 W/m2.

5. Distinguish between the features of conducted EMI and radiated EMI.

Unit – 2 Part–A

1. List the EMI coupling methods

(i) Inductive coupling (ii) Capacitive coupling (iii) Radiative coupling & (iv) Conductive coupling

2. What is meant by ground coupled interference?

Electromagnetic interference resulting from an electromagnetic disturbance coupled from one

Circuit to another through a common earth or ground-return path.

3. What is crosstalk with reference to EMI/EMC design issues?

Coupling of electromagnetic energy from one cable to another in multi-conductor transmission lines

results from magnetic field coupling when two cables are located close to each other. This electromagnetic energy

transfer or coupling from one transmission line to another is called Crosstalk. This is a most common source of

electromagnetic interference generation in electrical and electronics circuits.

4. How interference is avoided in power supply lines?

The interference is avoided in power supply lines: By using power line filter 2.Avoid unnecessary switching

operations, 3.Noisy circuits (with a lot of switching activity) should be physically separated from

the rest of the design. 4.Harmonic Wave Filters can be used. 5.Design for operation at lower signal levels, reducing

the energy available for emission.

5. Why is grounding essential to suppress EMI?

Electrical grounding is essential for the protection of personnel against electric shock, fire threat

Because of insulation burnout.





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6. What is radiated Coupling?

In this type of coupling, when the source and victim are separated by a long distance

Typically more than a wavelength. The source radiates the signal which may be wanted or

Unwanted and the Victim receives it in a way that disturbs its performance.

7. What is inductive Coupling?

This coupling occurs when a varying magnetic field exists between two parallel conductors,

Including a change in voltage along the receiving conductors and it is also called as magnetic

Coupling.

8. Define transient Coupling.

Electrical transients and other disturbances are induced in power lines as a result of natural EM

Phenomena and from the variety of equipment. Lightning can produce transients on power supply either

by direct strike or by strike or nearby structure.

9. Define Near-field coupling

This coupling occurs by changing electric or magnetic field that is a closer distance than one-sixth of wavelength.

10. How to reduce differential mode-coupling?

For balanced lines 1.Use Twisted wire pairs. 2. Add a single braided shield.

For unbalanced line. 1. Select coaxial cable with lower transfer impedance. 11.What is pigtail effect?

Pigtail effect used to connect the outer conductor of a co-axial line to a shielded box. It causes the shield current to be

concentrated on one side of the shield and liable to degrade shielding effectiveness.

12.How to reduce common-mode coupling?

1. Reduce ground loop area. 2.Reduce cable length. 3.Reduce average cable height.

4. Shield an entire susceptible area.

Part –B

1. Explain in detail the conducted, radiated and common impedance ground couplings with example.

The undesired or unintentional coupling of electromagnetic energy from one equipment (called emitter) to equipment

(called receptor) is the electromagnetic interference. The various methods of electromagnetic interference coupling

between an emitter and a receptor are illustrated in Figure.

Radiation Coupling

The radiation coupling between an emitter and a receptor results from a transfer of Electromagnetic energy through a

radiation path. Various types of radiation coupling are 1. Coupling of natural and similar electromagnetic environment

to the receptor, such as a power line. The power transmission line here acts as a receiving antenna. 2. Coupling of

electromagnetic energy from nearby equipment via direct radiation.

Conduction Coupling

The conduction coupling between an emitter and a receptor occurs via a direct conduction path between the emitter

and receptor. Examples of such coupling are: 1. Interferences can be carried by power supply lines when emitter and

receptor operate from the same power supply line. For example, common mains power supply is a frequent source of

conducted interference. 2. Interferences are also carried from emitter to receptor by signal or control lines, which are

connected between the two.

Common Impedance Coupling

Common impedance coupling occurs when currents from two different circuits flow through a common impedance..

The ground currents1 and 2 both flow through the common ground impedance. As far as circuit 1 is concerned, its

ground potential is modulated by ground current 2 flowing in the common ground impedance. Some noise, therefore,

is coupled from circuit 2 to circuit 1, and vice versa, through the common ground impedance.





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Inductive coupling and capacitive coupling.

The inductive coupling between two loops occurs in low series impedance circuits and at low frequencies. The

capacitive coupling occurs in the presence of high impedance to the ground and is

Predominant at high frequencies.

Unit III Part A

1. What are the factors considered while improving shielding effectiveness?

1. Conductive contact, 2. Seam overlap, 3. Gasket/Seam contact points

2. Define Grounding?

(i) Grounding is a technique that provides a low resistance path between electrical or electronic

Equipment and earth or common reference low impedance plane to bypass fault current or EMI

Signal. (ii) It is used to protect against electrical shock, fire threat.

3. What is zoning?

(i) This is a technique to reduce noise and EMI of a board and so as to reduce the need for extra

PCB layers. (ii) Process of defining the placing of components in PCB in any traces.

4. What is meant by Shielding?

Electromagnetic Shielding is the technique that reduces or prevents coupling of undesired radiated electromagnetic

energy into equipment, so to enable it to operate compatibly in its electromagnetic environment. Electromagnetic

Shielding is effective in varying degrees over a large part of Th electromagnetic spectrum from DC to Microwave.

Part –B

1. Explain about Isolation transformers

The concept of common-mode and differential-mode interferences and described the application of isolation

transformers to suppress these interferences. Transformers are used to isolate ground current loops. In addition to a

desired magnetic coupling between the primary and secondary windings in a transformer , an EMI coupling between

the two ports of a transformer (two circuits) takes place through capacitance between the primary and secondary

windings.

Figure (a) Transformer coupler, (b) isolation transformer

2. Explain various methods of grounding with examples.

Grounding is a technique that provides a low resistance path between electrical or electronic equipment





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and earth or common reference low impedance plane to bypass fault current or EMI signal. (ii) It is used to protect

against electrical shock, fire threat. The signal ground network can be of different types

1. Single Point ground 2. Multi point ground and 3. Hybrid ground or floating ground

1. Single Point ground: In a single point grounding scheme , each sub system is grounded to

Separate ground planes (structural grounds , signal grounds , shield grounds , AC primary and secondary

Power grounds ).These individual ground planes from each subsystem are finally connected by shortest

Path to the system ground point of reference potential.

Multi point grounding

In Multi point grounding scheme, every equipment is heavily bonded to a solid conducting plane

Which is then earthed for safety purposes.

Hybrid grounding

In Hybrid grounding scheme, the ground appears as a single point ground at low frequencies and a Multi point ground

at high frequencies.

3. Explain various EMI Gaskets.

EMC gaskets are shielding arrangements used to reduce the leakage of electromagnetic energy at metal-to-metal

joints. Conductive gaskets, when properly compressed, provide electrical continuity between seam-mating surfaces.

Electrical properties of the gaskets are selected to be nearly identical to 'those of the shield in order to maintain a high

degree of electrical conductivity at the interface, and to avoid air or high resistance gaps. The performance of EMC

gaskets depends on junction geometry, contact resistance, and the force applied at these joints

Knitted Wire-Mesh Gaskets

This gasket is produced in rectangular, round, round with fin, or double-core cross sections. Standard materials

generally used for galvanic compatibility with mating surfaces to minimize corrosion are tin-plated phosphor bronze,

tin-coated copper-clad sheet, silver-plated brass, Monel, stainless steel, or aluminum. These are used for minimizing

leakage of electromagnetic energy at enclosure joints, door contacts, and cables. An arrangement consisting of two

covers of knitted wire mesh over a neoprene or silicone closed cell sponge substrate gives excellent compression and

deflection characteristics.





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A double-layered strip of knitted wire mesh is also available in the form of shielding tape for cable assemblies, and is

recommended for EMI shielding, grounding, and static discharge applications. The mesh-wire is made of solid steel

core of circular cross-section and cladded with copper, and finally coated with tin as shown in Figure.

Figure. Mesh wire of a double-layered strip of knitted wire-mesh

Other gasket materials are formed by die-compressing a controlled amount of knitted wire-mesh into rings with holes

or mounting recesses. These are used for EMI shielding in cable TV, microwave ovens, waveguide flanges, and

connector and filter mountings.

Conductive Elastomer : Conductive elastomer gaskets are formed by filling silicone elastomer with any of the

following conducting materials: silver-plated inert particles, pure silver, carbon particles, silverplated

Copper, nickel, or aluminum particles designed to achieve high shielding effectiveness and corrosion resistance. These

are available in sheets and a variety of standard cross-sections suitable for joints.

Conductive Adhesive: Conductive adhesive is used for bonding or installing various conductive silicone

Elastomer EMC gaskets. It is a thick paste of room temperature vulcanizing (RTV) silicone resin with pure silver used

as filler material to cure quickly at room temperature. It forms a flexible resilient conductive bond or seal.

Conductive Grease: This is highly conductive silver-filled silicone grease without carbon or graphite. The electrical

conductivity and lubricating properties are maintained over a broad environmental range. This material is used in

power substation switches and in suspension insulators to reduce electromagnetic interference caused by arcing and

corrosion. The volume resistivity of this grease is typically of the order of 0.02 ohm-cm.

Conductive Coatings: Conductive coatings are organic-type paints densely filled with conductive particles,

such as graphite, silver, or nickel These are used for shielding and grounding plastic enclosures, which are susceptible

to EMI, and can be applied using a conventional spray system. The material usually contains a flammable solvent, and

must be used in a well-ventilated area to avoid fire hazard, inhalation, and direct skin contact. For best results, the

application surface must be cleaned of grease, oils, dirt, and any other foreign matter.

Unit IV PART A

1. What is need for standards?

The EMC standards are required for trouble free co-existence and to ensure satisfactory operation. They are also

required to provide compatibility between electrical, electronic, computer, control and other systems. Standards are

required as manufacturer-user interaction and user’s knowledge on EMI are limited. They are also required for

establishing harmonized standards to reduce international trade barriers and to improve product reliability and life of

the product.





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2. What are the types EMC STANDARDS?

There are two of standards: Military Standards and Civilian Standards

Military Standards

Military EMC standards are made in order to ensure system-to-system compatibility in the real time military

environment. Military standards are more stringent than civilian standards. Most of the military standards are broadly

based on MIL-STD 461 and 462.

Civilian Standards

The civilian EMC standards are applicable for equipments used for commercial, industrial and domestic applications.

The emission standards are specified to protect the broadcast services from interference.

3. What are the advantages of EMC standards?

The advantages are: 1. Compatibility, reliability and maintainability are increased.

2. Design safety margin is provided. 3. The equipment operates in EMI scenario satisfactorily.

4. Product life and profits are increased.

.4. What are the EMC STANDARDS IN DIFFERENT COUNTRIES?

S. No. Standard

Name

Meaning Country

1. CISPR

(IEC)

Committee International Special

Perturbations Radio electriques – Europe International

committee

2. FCC Federal Communications

Council USA

3. SAE Society of Automobile Engineers

Trade Association Technical

Committee

4. VG Military standard Germany

5. VDE Verband Deutscher Electro tecknikev Germany

6. ISI EMI measurements & measuring apparatus India

Part – B

1.Why do the standards vary with reference to civilian and military applications? What are the

various standards for civilian applications? How do they evolve? Discuss them in detail.

NEED FOR EMC STANDARDS:

The EMC standards are required for trouble free co-existence and to ensure satisfactory operation. They are also

required to provide compatibility between electrical, electronic, computer, control and other systems. Standards are

required as manufacturer-user interaction and user’s knowledge on EMI are limited.

They are also required for establishing harmonized standards to reduce international trade barriers and to improve

product reliability and life of the product.

EMC STANDARDS: These are of two types a) Military Standards b) Civilian Standards

a) Military Standards: Military EMC standards are made in order to ensure system-to-system compatibility in the real

time military environment. Military standards are more stringent than civilian standards. Most of the military

standards are broadly based on MIL-STD 461 and 462.

b) Civilian Standards: The civilian EMC standards are applicable for equipments used for commercial, industrial and

domestic applications. The emission standards are specified to protect the broadcast services from interference.

ADVANTAGES OF EMC STANDARDS

The advantages are: 1. Compatibility, reliability and maintainability are increased. 2. Design safety margin is

provided. 3. The equipment operates in EMI scenario satisfactorily. 4. Product life and profits are increased.

Basic Standard: Basic standards for the measurement of radio disturbance in the frequency range 9kHz - 18GHz. ex:

CISPR 16 Series, IEC/EN/K 61000-4 Series for ESD, RS/CS, Surge, EFT burst tests

Generic Standard: Generic standards – Immunity (EMS) and emission (EMI) for residential, commercial and light-

industrial environments. ex: IEC/EN/K 61000-6-1 & IEC/EN/K 61000-6-2 for EMS ,IEC/EN/K 61000-6-3 &

IEC/EN/K 61000-6-4 for EMI.

Product Family Standard: ex: CISPR 11(ISM), CISPR 12(vehicles, boats, combustion engine), CISPR 13(EMI for

broadcasting receiver), CISPR 14-1(EMI for home appliances), CISPR 14-2(EMS for home appliances),CISPR

15(lightening equipment), CISPR 2013(EMS for broadcasting receiver), CISPR 22(EMI for ITE), CISPR 24(EMS for

ITE), CISPR 25(vehicles, boats, combustion engine),CISPR 32 and CISPR 35(multimedia), etc.





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Product Standard: ex: IEC 60945(Maritime Navigation and Radio communication Equipment and Systems) ,

IEC 60533(Electrical and electronics installation in ships), IEC 61326(Electrical equipment for measurement, control

and laboratory use), IEC 61131-2(Programmable controllers), IEC 61204-3(Low voltage power supplies), etc.

2.Explain the principal of operation of TEM Cell (or) Explain the step-by-step approach for evaluating RE

and RS using TEM cell. Constructional details of a typical TEM cell are shown in figure . A TEM cell is a rectangular coaxial transmission

line, resembling a stripline, with outer conductors closed and joined together. The rectangular section is tapered at

both ends and matched to a 50-Q coaxial transmission line. The center conductor and an outer conductor (fanned by

top and bottom plates and the two side plates, which are all joined together) facilitate the propagation of

electromagnetic energy from one end of the cell to the other end in TEM mode. The center conductor is firmly held in

position by a number of dielectric supports. The EUT is placed in the

Rectangular part of the transmission line between the bottom plate and the center conductor, or

Between the center conductor and the top plate. A dielectric material spacer (with dielectric constant as close to unity

as possible) is used to electrically isolate the EUT from outer and inner conductors of the transmission line. Note that

the presence of a closed outer conductor serves as an effective shield to isolate the electromagnetic environment inside

a TEM cell from the electromagnetic environment outside of the cell. This ensures that the external electromagnetic

environment will not affect the measurements made inside the cell. Likewise any high-intensity fields generated

during tests will be confined to the interior of the cell.

Measurements Using TEM Cell :

There are many laboratories using TEM cells for EMI/EMC measurements throughout the world. They have

developed their own variation(s) of the approach to measurements and interpretation of results with the object of

obtaining as accurate results as possible. However, the pioneering and most intensive work in the development and

application of TEM cells for EMI/EMC measurements was done at the National Institute of Standards and

Technology. The detailed procedures they published for the measurement of radiation susceptibility and radiated

emissions are described in the following.

Fig. Block diagram for electromagnetic susceptibility testing of equipment





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3. Explain about MIL-STD-461 standard

MIL-STD-461 Requirements. MIL-STD-46 1 is the general specification for emission and susceptibility requirements

for military equipment. It requires that the testing be conducted within a shielded enclosure. RF absorber material

(carbon-impregnated foam pyramids, ferrite tiles, and so forth) should be used when performing electric field radiated

emissions or radiated susceptibility

Testing inside a shielded enclosure to reduce reflections of electromagnetic energy and to improve accuracy and

repeatability. The RF absorber is to be placed above, behind, and on both sides of the equipment under test and behind

the radiating or receiving antenna. The minimum normal incidence performance of the absorber is to be 6 dB from 80

MHz to 250 MHz, as well as 1 0 dB above 250 MHz.

4. Explain about open area test site measurements

Open site measurement is the most direct and universally accepted standard approach for measuring radiated

emissions from equipment, or the radiation susceptibility of a component or equipment.

Measurement of Radiated Emission:

In this setup, with the EUT switched on, the receiver is scanned over the specified frequency range to measure

electromagnetic emissions from the EUT, and determine the compliance of these data with the stipulated

specifications.

The basic principle of measurement for testing radiated emissions is illustrated in Figure

Measurement of Radiated Susceptibility

Figure 2 illustrates the principle for the measurement of radiation susceptibility. In this setup, the EUT is placed in an

electromagnetic field created with the help of a suitable radiating antenna. The induction field will predominate at

points close to the current element.

Unit V PART – A

1. What is LISN?

LISN means Line Impedance Stabilization Network. A network inserted in the supply mains lead of an apparatus to

be tested providing in a given frequency range a specified load impedance for the measurement of disturbance

voltages and possibly isolating the apparatus from the supply mains in that frequency range.

2. What are the two main objectives of LISN?

The two main objectives are:

(i) Provide constant impedance over range of frequency. (ii) Provide pure power without EM noise.

3. What are the four stages involved in EMC test?

The four stages involved in EMC test: Development test Pre-compliance test EMC compliance test





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And Production test

4. Mention the various type of EMC test.

The various type of EMC test conducted at the various stages during the development cycle are

Conducted emissions, Radiated emissions , Conducted immunity ,Radiated immunity,ESD immunity ,Transient

immunity and Surge immunity .

5. What is spectrum analyzer? List the types of spectrum analyzer. Spectrum analyzer is a broad band super heterodyne receiver which is used to display a wave in frequency domain

additionally, power measurements, side bands can also be observed. Types: Real time spectrum analyzer and Swept

tuned frequency spectrum analyzer

6. List some application of spectrum analyzer. Identifying frequency terms and their power levels, Measuring harmonic distortion in a wave

Determine type of wave modulation, Signal to noise ratio, For identifying wave distortion

Part – B

1. What are shielded chambers?

A variety of shielded enclosures can be used to control the testing environment. The three most common are the sheet

metal lined, prefabricated, and welded enclosures. Shielding materials commonly used in the construction of shielded

enclosures consist of the following:

1. Plywood/particleboard panels laminated on one or both sides with various grades of galvanized sheet

Metal are commonly used for prefabricated enclosures. Other metals, such as copper foil or screen, are

also fabricated in a similar manner.

2. Various thicknesses of sheet metal are welded into place on a steel supporting structure.

3. Aluminum foil is installed with contact adhesive, or moisture-proof sheetrock, which has aluminum foil

Bonded to one face of the board, is used.

4. Copper foil with a paper backing which is installed with contact adhesive or a nonwoven copper material

installed in like manner can form a single shield system.

5. Copper screening is mounted to wooden studs and spot soldered.

6. Galvanized sheet metal is mounted to plywood walls, resulting in a single shield system.

7. A combination of the above is used for specialized applications.

Generally, the basic shielding effectiveness of all the shielding material is adequate for most applications except in the

case of high power requirements or TEMPEST. Special techniques must be applied to meet these requirements. The

seams and doors of a shielded enclosure generally set the performance of a

given enclosure.

2. Describe Spectrum Analyzer in Detail with diagram. A spectrum analyzer or spectral analyzer or signal analyzer is a device used to examine the spectral composition

of some electrical, acoustic, or optical waveforms. It also measures the power spectrum.

A spectrum analyzer displays signal amplitude (strength) as it varies by signal frequency.

The frequency appears on the horizontal axis, and the amplitude is displayed on the vertical axis.

To the casual observer, a spectrum analyzer looks like an oscilloscope and, in fact, some lab

instruments can function either as an oscilloscope or a spectrum analyzer.

A spectrum analyzer is used to determine whether a wireless transmitter is working according to federally-defined

standards for purity of emissions. Output signals at frequencies other than the intended communications frequency

appear as vertical lines (pips) on the display .A spectrum analyzer is also used to determine, by direct observation, the

bandwidth of a digital or analog signal. A spectrum analyzer interface is a device that connects to a wireless receiver

or a personal computer to allow visual detection and analysis of electromagnetic signals over a defined band of

frequencies. This is called panoramic reception and it is used to determine the frequencies of sources of interference to

wireless networking equipment, such as Wi-Fi and Wireless routers.

There are analog and digital spectrum analyzers:

An analog spectrum analyzer uses either a variable band-pass filter or a super heterodyne receive With a band-pass

filter, the mid-frequency is automatically tuned (shifted, swept) through the range of frequencies of which the

spectrum is to be measured. With a super heterodyne receiver, the local oscillator is swept through a range of

frequencies.





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A digital spectrum analyzer computes the discrete Fourier transform (DFT), a mathematical process that transforms a

waveform into the components of its frequency spectrum.

Some spectrum analyzers (such as "real-time spectrum analyzers") use a hybrid technique where

the incoming signal is first down-converted to a lower frequency using super heterodyne techniques and then analyzed

using fast Fourier transformation (FFT) techniques.

3. Explain various testing antenna and their frequencies as specified in CISPR standard

Test for Radiated Emission (RE)

• RE Test for EUT ,Frequency Range : 30MHz to 1GHz(Up to 18GHz)

• Standard : CISPR 11, 12, 13, 25, 22… (EN 550XX) EEC 95/54, SAE J 1113-41

• Major Testing System (Refer to CISPR 16) ,Test Facility : OATS, ALSE, FAR, SAR Open area or alternate

test (anechoic chamber)

• Test Equipment : EMI Receiver(EMI test receiver), Spectrum Analyzer

• Test Antenna: Loop, Dipole, Log-periodic, Bi-conical Horn (depending on Frequency & Regulation) ,Other :

Turntable, Antenna Master, etc.

Test for Conducted Emission (CE)

• CE Measurement emitting from cable of EUT ,Frequency Range : 150kHz to 30MHz

• Standards: CISPR 11, 13, 14, 15, 25, 22.. (EN 550XX) ,Testing System (Refer to CISPR 16)

• Test Facility : Shielded Room or adequate ground planes

• Test Equipment : EMI Receiver, Spectrum Analyzer(Quasi-peak Average detector available)

• Other: LISN, (Line Impedance Stabilization Network) : To create a known impedance on power lines of

electrical equipment during electromagnetic interference testing. A LISN is typically designed to allow for

measurements of the electromagnetic interference existing on the power line.

Test for Radiated Susceptibility (RS)

• Radiated field susceptibility testing typically involves a high-powered source of RF or EM pulse energy and a

radiating antenna to direct the energy at the potential victim or device under test (DUT).

• Frequency Range :80 MHz to 1000 MHz ,Test condition :1-30 V/m (1 kHz CW, 80% AM) ,100 V/m

• Standards : IEC 61000-4-3 (EN 61000-4-3), ISO 11452-2

• Test Facility : FAR - Test Equipment : Power Amplifier system, Antenna, Field Probe Sensor, Signal

Generator, Directional Coupler, power meter, Other : Test software, etc

Test for Conducted Susceptibility(CS)

• Conducted voltage and current susceptibility testing typically involves a high-powered signal or pulse

generator, and a current clamp or other type of transformer to inject the test signal

• Frequency Range : 150kHz to 80MHz ,Test Condition : 1-10V (1kHz CW, 80% AM)

• Standards : IEC 61000-4-6 (EN 61000-4-6), ISO 7637 , Test System

• Test Facility : Shield Room ,Test Equipment : Power Amplifier system, Signal Generator,

Directional Coupler, power meter, CDN, Current Clamp ,Other : Test software, etc

Test for Electrostatic Discharge(ESD)

• ESD is a serious issue in solid state electronics, such as integrated circuits. Integrated circuits are made from

semiconductor materials such as silicon and insulating materials such as silicon dioxide. Either of these

materials can suffer permanent damage when subjected to high voltages; as a result, there are now a number

of antistatic devices that help prevent static build up.

• Test Condition(input voltage) : 8kV(Air Discharge), 4kV(Contact Discharge), Max 25kV

• Standard : IEC 61000-4-2 (EN 61000-4-2), ISO 10605 ,Test System

• Test Facility : Shield Room, Test Equipment : ESD Simulator, Coupling Plane ,

• Other : Capacitors, Resistors, etc

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