Dual receive ground terminal for use in communication systems utilizing multiple satellites

#This invention relates generally to satellite-based communication systems, and more particularly to a ground terminal design applicable to satellite-based communication systems having multiple satellites.

#Satellite-based communication systems which provide wireless access between separated user terminals on the earth are designed to give users of laptop PCs, handheld computers, and other similar devices very high-speed two-way data links with the Internet, their corporate Intranets, each other, and any other desired network. The service coverage is international, and utilizes high-power satellite transponders that route data from one user terminal to another.

#The satellite-based systems presently under consideration include at least two different types of satellite constellations. One type, such as that described as the Teledesic™ or ICO Global systems, provides a plurality of satellites in low-earth or medium-earth orbits, in which satellites enter and exit from view of a user terminal and require handoffs from one satellite to another as the individual satellites traverse into and out of view of a particular user. These handoffs typically occur via intersatellite crosslinks which route incoming data from a user from one satellite to the next. These intersatellite crosslinks are expensive to manufacture, are heavy and thus increase launch costs, take up valuable real estate on the satellite, and consume precious power.

#Reference is now made to the Description of the Preferred Embodiments, illustrated in the accompanying drawings, in which:

#FIG. 1 is a schematic illustration of the principles of a multiple satellite communication system, showing the basic configuration of two satellites and two user terminals; and

#FIG. 2 is a detailed schematic illustration of the ground user terminal of the present invention.

#Referring now more particularly to FIG. 1, therein is shown a communications system 10 illustrating the principles of the invention. The system 10 includes a first orbiting satellite 12 and a second orbiting satellite 14. The satellites 12, 14 are preferably in geostationary orbit approximately 36,000 kilometers above the surface of the earth, and would be located in the same node along the geostationary arc. For example, both satellites could be located at 97° West longitude to provide coverage of the continental United States.

#The satellite 12 includes four antennas: a user uplink antenna 16, a user downlink antenna 18, and gateway antennas 20, 22. The second satellite 14 also includes four antennas: the user uplink antenna 26, the user downlink antenna 24, and the two gateway antennas 28, 30. The four antennas shown for each satellite are illustrative. The functionality illustrated by these four antennas can be realized by fewer than four individual physical antennas. For example, transmit and receive functions can be realized by one antenna; and multiple beams can be realized with one antenna with multiple feeds.

#Each satellite 12, 14 also includes a payload 32, 34 respectively, which routes incoming RF signals from the uplink antenna 16, 26 to the downlink antenna 18, 24 respectively. The payloads 32, 34 may also provide processing of the incoming RF signals if desired.