ABSTRACT
The International Maritime Satellite Organization (INMARSAT) provides worldwide mobile satellite communication services for maritime, land, and aeronautical users. The antenna has no tracking function. The antennas used for INMARSAT-C are usually omnidirectional ones such as a quadrifiler helix, a crossed-drooping dipole, and a microstrip patch. A quadrifiler antenna has been the most popular type for installation on ships because of its good performance of widebeam coverage under the condition of ship motion. The kinds of antennas used for the M system depend on whether the terminals are used for maritime, land mobile, or handheld applications. In case of maritime applications, the configuration of externally mounted equipment for ships is basically the same as that of the INMARSAT-B system. Worldwide commercial aeronautical satellite communication services have been provided by the INMARSAT since 1990. In the INMARSAT system, INMARSAT-M and -C earth stations have been used not only by maritime users but also by land mobile users such as trucks and trains.
