Short note on EMI & EMC
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Transcript of Short note on EMI & EMC
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…