Electrical engineering

Definition of Electric Circuit : An electric circuit is a collection of electrical devices and components connected together for the purpose of processing information or energy in electrical form. An electric circuit may be described mathematically by ordinary differential equations, which may be linear or nonlinear, and which may or may not be time varying. The

GEO is also called as geosynchronous (or synchronous) orbits, which has 24 hour period of revolution but are inclined with respect to equator. Orbits that are below a mean altitude of about 36,000 km have periods of revolution shorter than 24 hours and hence are termed as non Geostationary Earth Orbit (GEO). Geostationary Earth Orbit

The communication is established to the satellite through earth station. The earth station can be located on the ship at the sea, or it can be located on the space craft or actually on the earth. The location of the earth station is decided depending upon the ease of control of satellite and the function

We know that the satellite can receive and transmit one of the bands given in Table For each band, the uplink and downlink frequencies are separate. Frequency division multiplexing of the complete uplink and downlink range of frequencies can be done to transmit and receive many channels simultaneously. For example for ‘C’ band, the bandwidth

In TDMA, the time slots are available to the ground stations with full bandwidth. In FDMA, the frequency bands are available to the ground stations with continuous time availability. By combining these two multiple access techniques, a hybrid technique called Code Division Multiple Access (CDMA) can be formed. Frequency hopping can be used so that

The uplink and downlink carriers of the satellite are required to be modulated by the signal to be transmitted. The modulation can be analog or digital. In the earlier satellites analog modulations were dominant and therefore they were used in communication satellites. The analog voice and video transmission systems use frequency. modulation and frequency division

The communications satellites are used to carry telephone, television and data signals. The television and telephone signals are normally analog. The satellite earth station transmits these signals on the same link by multiplexing. Time division multiplexing (TDM) and frequency division (FDM) are the commonly used multiplexing techniques. FDM/FM for Telephone Systems Fig shows the block

The orbits of satellite can be rotated around the earth through various paths. These paths are called orbits of the satellite. These orbits are used to cover the specific application areas. Orbits of Satellite When the satellite is moving in the orbits, it stays in position because the centripetal force on the satellite balances the

Fig shows the block diagram of satellite communication system. The satellite consists of transmitters as well as receivers. They are also called as transponders. The satellite receives signals from earth station transmitter, processes them (filtering, amplification) and transmits towards earth station receiver. The terrestrial communication system transmits or receives signals to users. It acts as

Principle : The narrow beam of radio waves is aimed at particular part of space. The same channel is reused over the another narrow beam aimed at another part of the space. This division of space in different directions of base station through highly directional beams is called Space Division Multiple Access (SDMA). As shown