Electromagnetic Interference (EMI) A disturbance that affects an electrical circuit

due to either electromagnetic induction or electromagnetic radiation emitted from an external source.

Radio Frequency Interference (RFI) is a special class of EMI in which radio frequency transmissions (usually narrow-band) cause unintentional problems in equipment operation.

EMI is any undesirable electromagnetic emission or any electrical or electronic disturbance, man-made or natural, which causes an undesirable response, degradation in the performance of electrical equipment

The fundamental concept of electrical and electromagnetic interference involves an emanating source and an affected device or system.

The transfer of energy between systems can occur through radiation, conduction, or induction.

The actual transfer of energy is facilitated respectively through a transmission path, conductive path, or through magnetic coupling.

Electromagnetic Interference (EMI) is the result of electromagnetic (E/M) emissions. Every piece of electrically powered equipment transmits and receives E/M energy

Conductors are better antennas as the frequency increases

Since LANs operate at very high speeds there can be lots of problems due to EMI

Electromagnetic interference in analog TV signal

Propagation of emiElectro-magnetic interference propagate

through conduction over signal and power lines and through radiation in free space.

Sources of EMI Sources of emi can be separated in following

catgories-Incidental interferenceExternal noiseInter modulation distortionSpurious emissionAdjacent channel interferenceEnvironmental interference

Incidental InterferenceWhen a device is unable to distinguish

desired signal due to the reception of a strong signal.

Result of the issues relating to circuit design,shielding requirements etc which lead to the inability to reject these unwanted signal.

Incidental EI have potentially devastating effects on medical devices and airplane electronics.

External NoiseIt can be electromagnetic or electrical in

nature.Noise from electromagnetic source can vary

in intensity and period.Electrical sources are constant in narure.

Spurious EmissionTransmission of signals that are outside the

prescribed frequency band of a transceiver are considered spurious emissions.

It involves harmonics at multiples of fundamental frequency.

Types of EMIDepending on the frequency ranges over which an interference

extends, it can be classified into two types:-Narrowband interferenceBroadband interferenceHelps in analysing the effects of emi .

Narrowband InterferenceNarrow band interference is electromagnetic radiation broadcasted

by TV and radio stations, as well as cell phones.These types of interferences are confined to certain

select frequency bands and are therefore known as narrow band electromagnetic interferences.

Narrowband interference usually arises from intentional

transmissions such as radio and TV stations, pager

transmitters, cell phones, etc.

Effects of Narrowband interference Mobile phones are one of the cases of its effects.Mobile Phone causes speaker interference any

time when it has an incoming call or is connecting to the service after being shut off.

It causes speakers to sort of blip in and out on the nearby speakers

Cause of the problemNarrowband electromagnetic interference is the culprit in this case.Mobile phone must emit electromagnetic waves (like microwaves,

x-rays, or radio waves) to communicate with a tower.This communication is kept open all the time, and is increased

when on a call, or when the phone switches from one tower to the next.

As the phone sends and receives bursts of electromagnetic waves from the tower, the waves impart voltage in a circuit which makes cut-out silence, or noises from the speakers.

Broadband interference

The power density of electromagnetic interference in an average

urban environment since 1945.

CAUSES OF EMI