TABLE OF CONTENTS Yoshihiko Konishi
Takayasu Shiokawa
Yasuhiro Kazama
The 1990s were an era of mobile satellite communications serviced on a commercial basis. Since 1982, the International Maritime Satellite Organization (INMARSAT) system has provided international maritime satellite communication services and is expanding the services to aircraft and land mobiles. Also, systems such as American Mobile Satellite Corporation (AMSC) in the United States, MSAT in Canada, and AUSSAT in Australia [1] provide domestic satellite communication services mainly for land mobiles using dedicated satellites. The research and development activities on mobile satellite communication have continued since the mid-1970s in many countries and organizations. Typical research programs are MSAT in the United States [2] and Canada [1], the ETS-V in Japan [3], and PROSAT in Europe [4].
The mobile communication systems mentioned above use Geostationary Earth Orbiting (GEO) satellites. However, several private companies have proposed new systems called Low Earth Orbiting (LEO) and Medium Earth Orbiting (MEO) satellite communication systems, and these use a group of low-altitude orbiting satellites. Typical examples of LEO/MEO satellite systems are Iridium, Odyssey, Globalstar, and ICO, which use 66, 12, 48, and 10 satellites, respectively. The main advantage of LEO/MEO satellite systems from the point of view of antenna design is that mobile and handy terminals can use low-gain omnidirectional antennas, because of smaller values of free-space propagation loss compared with those of GEO satellite systems. Furthermore, several broadband mobile satellite communication systems have been proposed using the Ku-band (14/12 GHz) GEO satellites in the 21st century. Connexion by...
