Satellite 101: Introduction to Satellite Communication

A satellite network is a combination of modes that provide communication from one point on the earth to other. A node in the network can be a satellite an earth station, or any end user terminal or a telephone. Although a real satellite such as the moon can be used as a relaying node in the network, the use of artificial satellites is preferred because we can install electronic equipment on the satellite to regenerate the signal that has lost its energy during travel. Another restriction of using a natural satellite is their distances from the earth which create a long delay in communication. Satellite networks are like cellular networks in that they divide the planet into large cells. Satellites can provide transmission capability to and from any location on earth no matter how remote it is. This advantage makes high quality communication available to undeveloped parts of the world without requiring a huge investment in ground based infrastructure. An artificial satellite needs to have an orbit, the path in which it travels around the earth. The orbit can be equatorial, inclined or polar. The period of a satellite that is the time required for a satellite to make a complete trip around the earth is determined by Kepler’s law which defines the period as a function of the distance of the satellite from the centre of the earth. Satellites process microwaves with bi directional antennas that is line of sight. Therefore the signal from a satellite is normally aimed at a specific area called the footprint. The signal power at the centre of the footprint is highest. The power decrease as we move from the foot print centre. The boundary of the foot print is the location where the power reaches a pre defined threshold. Based on the location of orbits satellites can be divided into three categories that is geosynchronous earth orbit, low earth orbit and medium earth orbit. Location of orbits is the distance of orbits from earth’s surface. One reason for having different reasons is due to the existence of two Van Allen belts. A Van Allen is a layer that contains charged particles. A satellite orbiting in one of these two belts would be totally destroyed by the energetic charged particles. The medium earth orbits are located between these two belts. The frequencies reserved for satellite microwave communication are in gigahertz range. Each satellite sends and receives over two different bands. Transmission from the earth to the satellite is called uplink and transmission from the satellite to the earth is called downlink. Compared to the fiber optical communication, satellite communication has the advantage that the quality of transmitted signal and location of sending and receiving stations are independent of distances.

About the Author

Tymon Hytem has worked in the electronics feild for the past 15 years. He enjoys helping people decide on electronic gadgets from telephones to XM Radio and choosing the perfect XM Satellite Radio system for their needs.