 Hello everyone, welcome to a video lecture on basics of satellite communication. Myself, K.R. Viradhar, assistant professor, department of electronic and telecommunication engineering, Valtran Institute of Technology, Sholapur. Let us start with the learning outcomes first. At the end of this session, students will be able to define and explain satellite communication basics. First, we will come to know what is satellite? Satellite is basically any object that revolves around a planet in a circular or elliptical path. Satellite is an object, basically it is an object which revolves around in a planet, either it takes circular or elliptical path. But when you consider the artificial satellite and it is also called man-made object, it also orbiting the earth in a solar system. So, artificial satellites which are revolved around the earth. A practical scenario of earth station you can see here, so earth is revolving at the same speed, satellite also revolving. This is an animation of geosynchronous satellites because geosynchronous satellites revolve at the same speed of the earth, satellite communication system. The schematic shows the satellite communication system. It consists of mainly transmitting station, receiving station and the satellite. When you consider terrestrial communication, you have three things. One is transmitting station, other one is the receiving station, in between that some repeaters are placed. So, there is a problem between transmitting and receiving station, there is no direct line of path. In such a case, we need to place one repeater. What the repeater does? It takes the signals from the transmitting station and remove noise and amplify the signal and retransmit to the receiving station. So, here satellite makes exactly same as the repeater in terrestrial communication. It takes the signals from the transmitting station, remove noise and amplify the signals and retransmit to the receiving earth stations. The transmitting earth station signals sends to the satellite through uplink. That means, the process of transmitting the signals from earth station to the satellite is called uplink. So, the signal received at the satellite from the transmitting earth station will remove noise and amplify the signals and retransmit again to the receiving earth station through the downlink. The process of transmitting from the satellite to the receiving earth station is called the downlink. In this slide, we shall see different types of satellites. Satellites are basically classified are of three types. One is Geo, Mio and Leo. Geo means geostationary earth orbit that is also called geostationary satellites. Other one is the Mio, it is also called medium earth orbit. Third one is Leo that is also called the low earth orbit. Geostationary satellites are placed at a distance of 36,000 kilometer from the earth station. These are used for the communication applications whereas, Leo satellites are placed very close to the earth station. So, Mio stationers are medium earth orbit, medium earth orbits are placed between Geo and Leo. So, with the basic knowledge, can you guess what are the applications are use of a satellites? What are the different use of satellites? Pass this video, think and write your answers. We have huge number of applications in day to day lives. I think you might have written the answer. Let us see those. The uses of satellites are very essential in our daily lives. The various use of a satellites are first one weather reports. So, satellites are used to monitor the climatic and weather condition on the earth surface. Second one is direct to home that is also called television transmission by direct TV. These are used to connect signals from broadcasting TV station to the TV present in your home via satellites. When a telephone calls taking image of earth, we can take the image of earth from the satellites. Global positioning system, this is one of the most important application of satellites which is used to locate the GPS system. The various advantages of satellite communication over terrestrial are the coverage area of a satellite is large. Using satellite, you can have a large coverage area. Transmission cost of satellite is independent of coverage area. Even if you want to increase the coverage area, but the cost of the system will not increase. Whereas in the terrestrial communication, we need to increase the cable cost because we need to install more cables and more length cable means more cost. Satellite to satellite communication is very precise. So, we can transmit the signals from earth station to one satellite again from one satellite to another satellite then to the receiving earth station that can be precise and accurate. Higher bandwidths are available for use a large bandwidth in terms of gigahertz are available in satellite communications. The various disorient is of satellites are launching satellites into orbit is costly. So, to build the satellite and to launch the satellite for a and place it in a such a higher orbit around 36,000 kilometer, the cost of the total launching will be become high. Satellite bandwidth is a gradually becoming used up. So, once if you use a certain bandwidth, so same bandwidth cannot be used. So, almost all bandwidths are used up that is also one of the disadvantage of satellite. Large propagation delay in satellite communication, if I want to transmit a signal from transmitting station to receiving station for example, from one person to another person around a 10 kilometer what happens in terrestrial communication we can transmit directly through the cable. Whereas in the satellite communication what happens we need to send the signal from transmitting station to the satellite and then from satellite again to the receiving station here the delay which is going to take or propagation delay which is going to take in increase. These are the frequency bands for satellite communications. We can see in the first column there are various bands available and the second column in the range of frequencies is used for each band and total available band in the third column and their general applications. In these bands of frequencies the most commonly used are C, KU and KA bands those are discussed in the next slides. Commonly used frequency bands are three those are C band, KU band and the KA band. The C band frequency range is around 4 to 8 gigahertz the most commercial satellites are used in this band. The bandwidth allocated for this C band is around 500 megahertz. This band is also known as 4 by 6 gigahertz band. KU band the frequency range is 12 to 18 gigahertz, KU band is primarily used for communication satellites. The KU band has electromagnetic spectrum in the micro range of frequencies. KA band the KA band frequencies is range is 26 to 40 gigahertz. The KA band covers the frequencies of 26.5 to 40 gigahertz. The 30 by 20 gigahertz band is used in communication satellites. So, these are used in high resolution close range targeting radars. These are also used in abroad military airplanes. These are the references used to prepare the above PPT. Thank you.