hrvatski

Globalni mobilni satelitski sustavi

Global Mobile Satellite Systems (GMSS) are widely used nowadays and play a very important role within the global mobile system. Satellites enable us to determine position of objects on Earth, to transfer all sorts of digital data and what is even more important, to make a speech transfer over large distances. For all these reasons they deserve to be called multifunctional. GMSS satellites are LEO satellites, divided into three subgroups. These are Low Earth Orbit satellites, characterized by very short delay time, which makes them a perfect solution for this purpose. Each group is special. Small LEO is used for file transferring, Big LEO for speech transferring and Broadband LEO for all sorts of services using wide frequency specter. Through new and sophisticated equipment built into satellites, engineers have found a way to deal away with Doppler Effect, one of the physical problems associated with satellites due to extremely high speeds. This work presents the concept of satellite and outlines its principle of work. It contains crucial facts about Global Mobile Satellite System. All sorts of LEO satellites are analyzed along with the services they offer. It introduces the elementary phenomenon of the Doppler Effect as well as the calculation of propagation in RFPROP program, showing that with real parameters satellites enable a very efficient communication and a quality transmission of signal over wide distances.

LEO; satelit; mobilni sustav; komunikacija; putanja; Dopplerov efekt; Van Allenov

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