February 05, 2020
Amitraj
Unguided Media -
-> It is also known as unbounded or wireless media.
-> An unguided transmission transmits the electromagnetic waves without using any physical medium.
-> In unguided media, air is the media through which the electromagnetic energy can flow easily.
Features
1. Signal is broadcasted through air
2. Less Secure
3. Used for larger distances
Unguided transmission is classified into three categories:-
1. Radio Waves -
-> Radio waves are the electromagnetic waves that are transmitted in all the directions of free space.
-> Radio waves are omnidirectional, i.e., the signals are propagated in all the directions.
-> The range in frequencies of radio waves is from 3Khz to 1 Ghz.
-> In the case of radio waves, the sending and receiving antenna are not aligned, i.e., the wave sent by the sending antenna can be received by any receiving antenna.
-> Ex: FM radio.
Advantages Of Radio transmission:
1. Radio transmission is mainly used for wide area networks and mobile cellular phones.
2. Radio transmission provides a higher transmission rate.
2. Microwaves
Electromagnetic waves having frequencies between 1 and 300 GHz are called micro waves. Micro waves are unidirectional. When an antenna transmits microwaves, they can be narrowly focused. This means that the sending and receiving antennas need to be aligned.
Microwaves are of two types:
1. Terrestrial microwave
2. Satellite microwave communication.
Terrestrial Microwave Transmission
-> Terrestrial Microwave transmission is a technology that transmits the focused beam of a radio signal from one ground-based microwave transmission antenna to another.
-> Microwaves are the electromagnetic waves having the frequency in the range from 1GHz to 1000 GHz.
-> Microwaves are unidirectional as the sending and receiving antenna is to be aligned, i.e., the waves sent by the sending antenna are narrowly focussed.
-> In this case, antennas are mounted on the towers to send a beam to another antenna which is km away.
Advantages Of Microwave:
1. Microwave transmission is cheaper than using cables.
2. It is free from land acquisition as it does not require any land for the installation of cables.
Disadvantages of Microwave transmission:
1. Out of phase signal: A signal can be moved out of phase by using microwave transmission.
2. Bandwidth limited: Allocation of bandwidth is limited in the case of microwave transmission.
Satellite Microwave Communication
-> A satellite is a physical object that revolves around the earth at a known height.
-> Satellite communication is more reliable nowadays as it offers more flexibility than cable and fibre optic systems.
-> We can communicate with any point on the globe by using satellite communication.
How Does Satellite work?
The satellite accepts the signal that is transmitted from the earth station, and it amplifies the signal. The amplified signal is retransmitted to another earth station.
Advantages Of Satellite Microwave Communication:
1. The coverage area of a satellite microwave is more than the terrestrial microwave.
2. Satellite communication is used in mobile and wireless communication applications.
3 .It is easy to install.
Disadvantages of Satellite Microwave
1. Satellite manufacturing cost is very high.
2. Cost of launching satellite is very expensive.
3. Infrared
-> An infrared transmission is a wireless technology used for communication over short ranges.
-> The frequency of the infrared in the range from 300 GHz to 400 THz.
-> It is used for short-range communication such as data transfer between two cell phones, TV remote operation, data transfer between a computer and cell phone resides in the same closed area.
Characteristics Of Infrared:
1. It supports high bandwidth, and hence the data rate will be very high.
2. Infrared waves cannot penetrate the walls. Therefore, the infrared communication in one room cannot be interrupted by the nearby rooms.
3. An infrared communication provides better security with minimum interference.
-> It is also known as unbounded or wireless media.
-> An unguided transmission transmits the electromagnetic waves without using any physical medium.
-> In unguided media, air is the media through which the electromagnetic energy can flow easily.
Features
1. Signal is broadcasted through air
2. Less Secure
3. Used for larger distances
Unguided transmission is classified into three categories:-
1. Radio Waves -
-> Radio waves are the electromagnetic waves that are transmitted in all the directions of free space.
-> Radio waves are omnidirectional, i.e., the signals are propagated in all the directions.
-> The range in frequencies of radio waves is from 3Khz to 1 Ghz.
-> In the case of radio waves, the sending and receiving antenna are not aligned, i.e., the wave sent by the sending antenna can be received by any receiving antenna.
-> Ex: FM radio.
Advantages Of Radio transmission:
1. Radio transmission is mainly used for wide area networks and mobile cellular phones.
2. Radio transmission provides a higher transmission rate.
2. Microwaves
Electromagnetic waves having frequencies between 1 and 300 GHz are called micro waves. Micro waves are unidirectional. When an antenna transmits microwaves, they can be narrowly focused. This means that the sending and receiving antennas need to be aligned.
Microwaves are of two types:
1. Terrestrial microwave
2. Satellite microwave communication.
Terrestrial Microwave Transmission
-> Terrestrial Microwave transmission is a technology that transmits the focused beam of a radio signal from one ground-based microwave transmission antenna to another.
-> Microwaves are the electromagnetic waves having the frequency in the range from 1GHz to 1000 GHz.
-> Microwaves are unidirectional as the sending and receiving antenna is to be aligned, i.e., the waves sent by the sending antenna are narrowly focussed.
-> In this case, antennas are mounted on the towers to send a beam to another antenna which is km away.
Advantages Of Microwave:
1. Microwave transmission is cheaper than using cables.
2. It is free from land acquisition as it does not require any land for the installation of cables.
Disadvantages of Microwave transmission:
1. Out of phase signal: A signal can be moved out of phase by using microwave transmission.
2. Bandwidth limited: Allocation of bandwidth is limited in the case of microwave transmission.
Satellite Microwave Communication
-> A satellite is a physical object that revolves around the earth at a known height.
-> Satellite communication is more reliable nowadays as it offers more flexibility than cable and fibre optic systems.
-> We can communicate with any point on the globe by using satellite communication.
How Does Satellite work?
The satellite accepts the signal that is transmitted from the earth station, and it amplifies the signal. The amplified signal is retransmitted to another earth station.
Advantages Of Satellite Microwave Communication:
1. The coverage area of a satellite microwave is more than the terrestrial microwave.
2. Satellite communication is used in mobile and wireless communication applications.
3 .It is easy to install.
Disadvantages of Satellite Microwave
1. Satellite manufacturing cost is very high.
2. Cost of launching satellite is very expensive.
3. Infrared
-> An infrared transmission is a wireless technology used for communication over short ranges.
-> The frequency of the infrared in the range from 300 GHz to 400 THz.
-> It is used for short-range communication such as data transfer between two cell phones, TV remote operation, data transfer between a computer and cell phone resides in the same closed area.
Characteristics Of Infrared:
1. It supports high bandwidth, and hence the data rate will be very high.
2. Infrared waves cannot penetrate the walls. Therefore, the infrared communication in one room cannot be interrupted by the nearby rooms.
3. An infrared communication provides better security with minimum interference.
