Satellite

Introduction:-

                             Satellite communication is the method of transporting information from one place to another using a communication satellite in orbit around the Earth. 

A communication satellite is an artificial satellite that transmits the signal via a transponder by creating a channel between the transmitter and the receiver located at different locations on the Earth.


Telephone, radio, television, internet, and military applications use satellite communications. 

The frequency with which the signal is sent into the space is called Uplink frequency, while the frequency with which it is sent by the transponder is Downlink frequency.

                Satellite Communication Block Diagram



Working Principle:-

                                        The communication satellites are similar to the space mirrors that help us in bouncing the signals such as radio, internet data, and television from one side of the earth to another. There are three stages that are involved which explain the working of satellite communications. These are:
i) Uplink
ii)Transponders
iii)Downlink

Uplink:
Let’s consider an example of signals from a television. In the first stage, the signal from the television broadcast on the other side of the earth is first beamed up to the satellite from the ground station on the earth. This process is known as uplink.
Transponder:
The second stage involves transponders such as radio receivers, amplifiers, and transmitters. These transponders are used for boosting the incoming signal and to change their frequency so that the outgoing signals are not altered. Depending on the incoming signal sources, the transponders vary.
Downlink:
The final stage involves a downlink in which the data is sent to the other end of the receiver on the earth. It is important to understand that usually there is one uplink and multiple downlinks.


Advantages:
Area of coverage is more than that of terrestrial systems
Each and every corner of the earth can be covered
Transmission cost is independent of coverage area
More bandwidth and broadcasting possibilities


Disadvantages:
 Launching of satellites into orbits is a costly process.
Propagation delay of satellite systems is more than that of conventional terrestrial systems.
Difficult to provide repairing activities if any problem occurs in a satellite system.
Free space loss is more
There can be congestion of frequencies.


Application areas:-

1) Satellite communication plays a vital role in our daily life. Following are the applications of satellite communication −
2) Radio broadcasting and voice communications
3) TV broadcasting such as Direct To Home (DTH)
4) Internet applications such as providing Internet connection for data transfer, GPS applications, Internet surfing, etc.
5) Military applications and navigations
6) Remote sensing applications
7) Weather condition monitoring & Forecasting