| 摘要 |
A satellite-based communications system operating at high data rates in a broadcasting (multicasting) mode enables the use of mobile ground terminals with low profile antennas whose areas are significantly smaller than previous embodiments not using this invention. The invention can be applied to existing (in-orbit) or new satellites (including those in non-geostationary orbits) operating with linearly polarized downlink transponders. Important embodiments include the use of Ku FSS satellites providing service within the continental U.S. ("CONUS"), and the use of Ku BSS satellites operating within Europe. Transponder pairs on board the satellite with opposite linear polarization, but overlapping frequency bands, receive a specially processed uplink waveform from an uplink facility. Service may be optimized for (1) a particular geographical area by using receiving sensors located in that area, monitoring the polarization of the broadcast signal; or (2) a particular location with the satellite operating in a unicasting mode (delivery of Internet data or "local" video/audio broadcasts). A spread-spectrum waveform can also be used on the downlink, with the resultant processing gain applying directly to antenna area reduction and improved interference. Redundancy or increased capacity can be achieved by locating a second satellite in the same orbital location broadcasting the orthogonal circular (as received on the ground) polarization.
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