Antennas for the next generation of mobile satellite services

The current generation of mobile satellite service (MSS) requires Earth terminals that produce an antenna beam directed to a satellite. The MSS is making an incremental leap forward to hand held terminals in the next four years. For the first time, users will carry small satellite terminals which have hemispherical antenna patterns that do not point and, therefore, provide greatly enhanced freedom of movement. However, the simpler antenna on the user terminals has increased the burden on the satellite antenna. This paper derives general requirements for both user terminal antennas and satellite antennas. Important considerations include: the geometrical relationships between the satellites and users, satellite orbit altitude, gain & gain margin required for the communication links, ITU power flux density levels, battery life, and safety for the user. Odyssey^TM is used as an example of a typical MSS satellite system. This paper describes design trades and the baseline satellite and user terminal antennas which are envisioned for the Odyssey^TM system