Field theoryShort note on EMI & EMC

Prepared By:-Name Enrolment Number Roll Number

Chanchal Jain 140090109007 140907

Deval chotaliya 140090109010 140910

Sikha Jena 140090109021 140921

Dolen Patel 140090109038 140938

Yash patel 140090109049 140949

Krishna Parekh 150093109005 1509913

EMI

EMI (electromagnetic interference) is the disruption of operation of an electronic device when it is in the vicinity of an electromagnetic field (EM field) in the radio frequency (RF) spectrum that is caused by another electronic device.

Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrostatic coupling, or conduction.

The disturbance may degrade the performance of the circuit or even stop it from functioning.

In the case of a data path, these effects can range from an increase in error rate to a total loss of the data.

Both man-made and natural sources generate changing electrical currents and voltages that can cause EMI: automobile ignition systems, cell phones, thunder storms, the Sun, and the Northern Lights.

EMI frequently affects AM radios. It can also affect cell phones, FM radios, and televisions.

EMI can be used intentionally for radio jamming, as in electronic warfare.

Electromagnetic interference (EMI)

Basic elements of EMI situations

Source / Emitter / Culprit

Coupling Path /

Medium

Receiver / Receptor /

Victim

Interference occurs if the received energy causes the receptor to function in unwanted manner.

Whether the receiver is functioning in wanted or unwanted manner,depends on the coupling path as well as the source and victim.

The coupling path is to be made as inefficient as possible. 

EMI Culprit & Victim

Coupling path

Signal Reciever

Signal Source

EMI Source

Culprit

Victim

Common examples of EMI are:

Disturbance in the audio/video signals on radio/TV due an aircraft flying at a low altitude

Noise on microphones from a cell phone handshaking with communication tower to process a call

A welding machine or a kitchen mixer/grinder generating undesired noise on the radio

In flights, particularly while taking off or landing, we are required to switch off cell phones since the EMI from an active cell phone interferes with the navigation signals.

Sources Refrigerator, washing machine, electric

motors. Arc welding machine. Electric shavers, AC, computers. Fast switching digital devices, ICs. Power cords of computers, UPS etc. Air craft navigation and military

equipments.

Causes of EMI

Victims Communication receivers. Microprocessors, computers. Industrial controls. Medical devices. House hold appliances. Living beings.

Causes of EMI

EMI Coupling

Radiated Antenna-to-Antenna Case Radiation Case Penetration Field-to-wire wire-to-Field wire-to-wire

Conducted Power Lines Interconnecting Signal

Cables Common Ground

Impedance

EMI Coupling

Effects of EMI

Momentary disturbance in TV and radio reception due to operation of mixer-grinder / electric shavers/ a passing vehicle etc.

Reset of computers and loss of data. Burn out of sensitive cells / components. Change of setting of status of control equipments. Failure of pace maker implanted in a patient due to a ‘walkie

talkie’. False initiation of electro explosive detonator. Malfunctioning of flight controlling system due to use of

laptop by passenger. Biological hazards.

EMC

Electromagnetic compatibility (EMC) is the branch of electrical engineering concerned with the unintentional generation, propagation and reception of electromagnetic energy which may cause unwanted effects such as electromagnetic interference (EMI) or even physical damage in operational equipment.

The goal of EMC is the correct operation of different equipment in a common electromagnetic environment.

EMC pursues two main classes of issue.

1. Emission is the generation of electromagnetic energy, whether deliberate or accidental, by some source and its release into the environment. EMC studies the unwanted emissions and the countermeasures which may be taken in order to reduce unwanted emissions.

2. Susceptibility is the tendency of electrical equipment, referred to as the victim, to malfunction or break down in the presence of unwanted emissions, which are known as Radio frequency interference (RFI).

Purpose for EMC System

A system is said to be electro magnetically compatible if :-

It doesn't cause interference with other system. It is not susceptible to emissions from other

systems. It doesn’t cause interference with itself.

Methodology for EMC System

The methodologies to prevent EMI are Suppress the emissions at source point, best

method to control EMI. Make the coupling path as inefficient as possible. Make the receiver less susceptible to emission.

EMC CONTROL

FREQUENCYDOMAIN

TIMEDOMAIN

LOCATIONDOMAIN

DIRECTION DOMAIN

FREQUENCY ASSIGNMENT(FDMA)

TRANSMITTER & RECEIVER FILTERS

CDMA

ACTIVITYSYNCHRO-NIZATION

TDMA

CDMA

SEPARATION DISTANCE

NATURALTERRAIN .SHIELDING

ANTENNADIRECTIONFILTER

ANTENNAPOLARIZATIONFILTER

EMC limits

Emission limits: the maximum disturbance levels which the equipment is allowed to produce

Immunity limits: the minimum disturbance levels which the equipment should withstand without its operation being unacceptably degraded Different classes of EM environmental stress Standard ‘average’ conditions and performance

criteria, or ‘worst-case’ are to be distinguishedVerifying these limits may require special

(expensive!) EMC test equipment

Thank You…Thank You…