NOISE IN RADIO WAVES

Mr. Husnain Sherazi @leads.edu.pk

Lecture 3

Electromagnetic Waves• Waves can travel through space without any need of

medium.

• Light and Heat waves are example of these waves

which can travel through space without any medium.

• These waves are called electromagnetic waves.

• These waves can travel freely through space in all the

direction at the speed of light.

Radio Waves

Limitations of Electromagnetic Waves

• Electromagnetic waves have great speed but they

have certain limitations

• Light waves cannot penetrate through materials like wood etc.

• Heat waves cannot penetrate certain objects.

• Heat waves are absorbed by the surrounding objects.

• Because of these limitations, Light and Heat waves

have limited range.

• Similarly, intensity of these waves are also limited.

Radio Waves• Besides Light and Heat, there are some other types of

waves called Radio Waves.

• Electric current passing through the wires generates

magnetic field which can be spread out in the space.

• Using these Radio waves, information can be

transferred from one place to another.

• Radio waves also spread in all directions in space.

Characteristics Radio Waves• Radio waves can travel through long distances unlike

Light and Heat waves.

• Radio waves can penetrate through materials unlike

Light and Heat waves.

• Radio waves are invisible.

• Radio waves are normally not felt.

• Because of all these characteristics, radio waves are

superior means of communication in Computer

Networks.

Comparison of Waves

Noise in Wireless Communication• Various definitions are available.

• Noise is an unwanted disturbance in the wireless

signal.

• It is also defined as radio interference in radio

frequency of a wireless communication.

• Undesired signal interfering in a desired signal.

Effect of Noise• Effect of noise can vary from minor to major.

• Noise affecting the wireless signal can cause errors in

wireless communication.

• It can break a wireless communication.

• It can be misread by the receiver.

• Information, energy and cost can be wasted if large

amount of noise is present in a wireless

communication.

Types of Noise• In a wireless communication, there are various types

of noises that can affect the wireless signal.

• Normally noise is categorized as:

• Thermal Noise

• Intermodulation

• CrossTalk

• Impulse Noise

Types of NoiseThermal Noise

• The noise created when heat generated by an

electronic device is called a Thermal Noise

• Every electronic device is affected by Thermal Noise.

• Thermal noise is related to heat and is also called

White Noise

• If temperature of any device or transmission medium

is raised to an extent that heat is generated, thermal

noise will be produced.

Types of NoiseIntermodulation Noise

• This type of noise occurs when two different

frequencies enter a non-linear device.

• The mix of frequencies will create fake or improper

results causing the devices to malfunction.

• Mixers and power amplifiers normally cause this type

of noise.

• These kind of noises can be reduced by aligning the

frequencies and increasing the linearity of device.

Types of NoiseCrossTalk Noise

• The noise created by electrical coupling is called

CrossTalk.

• Electrical coupling is referred to as, the transfer of

electric current from one circuit segment to another.

• CrossTalk can also be created by poor control of

frequency between different circuit segments during

transmission of signal.

Types of NoiseImpulse Noise

• It is a series of non-continuous, irregular impulses for

a short duration.

• The amplitude of these impulses is normally very

high.

• It degrades the signal to a small extent, however, the

data is corrupted and might be meaningless when

received at the receiver.

• They are normally caused by corrupted media.

Terminologies in Radio Waves

• Gain

• It is the positive difference in amplitude of two

signals.

• It is sometimes also called Amplification.

• Gain can occur intentionally from some external

power source.

• Gain can occur unintentionally, when a wave

strikes some hurdle.

Terminologies in Radio Waves

• Gain

Terminologies in Radio Waves

• Loss

• It is the negative difference in amplitude of two signals.

• Loss can also be intentional or unintentional.

• Intentional loss can occur to meet the standards so that

signals do not interfere with other RF signals.

• Unintentional loss can occur because of

• Absorption

• Reflection

• Scattering

• Refraction

• Diffraction

Terminologies in Radio Waves

• Loss

Terminologies in Radio Waves

• Loss due to Absorption

• Some materials can absorb RF signals.

• These can be wood, concrete etc.

Terminologies in Radio Waves

• Loss due to Reflection

• Sometimes signals are reflected from surfaces like metal

surfaces with large areas.

Terminologies in Radio Waves• Loss due to Scattering

• Sometimes signals are scattered because of rough surfaces

like trees and rocks.

Terminologies in Radio Waves• Loss due to Refraction

• RF signal sometimes bend when enters from clear medium

to a dense medium e.g. from bright weather to a rainy

weather.

Terminologies in Radio Waves• Loss due to Diffraction

• Diffraction is caused when an object comes in the way of

the signal.