Engineering Tutorials

Satellite Communication using VSAT (Very Small Aperture Terminal) since the science fiction on radio transmission through space using geo-synchronous earth satellite, provider has progressed significantly in the field of satellite communications. The early earth stations were large and expensive. The reason for the size and complexity of the early stations was not related to inadequate performance. In fact, the antennas had very high efficiency and the noise temperatures of their receivers were low. However, the satellites at that time had a relatively poor performance providing considerably low RF (radio frequency) power per transponder and a rather high noise temperature for the on-board receivers. Additionally, satellites were then considered suitable only for very long distance communication. Gradually, satellite communications have appeared as regional systems requiring smaller coverage on the earth’s surface enabling higher gain antennas. Subsequently, increase in transponder out-put power, introduction of systems having several spot beams, development of field-effect transistor amplifier for low noise receivers as well as its availability as power amplifier have changed the satellite communication scenario. Once it was possible to envisage an all solid-state transmit and receive earth station even with a rather low power output, low price, large quantity, VSAT-based earth station design could be conceived.