Satellite communications system using multiple earth stations
First Claim
1. A communications satellite system for providing communications between a plurality of mobile terminals and a satellite ground station, said system comprising:
- at least one orbiting satellite comprising a satellite dual-polarization receiving antenna, said satellite dual-polarization receiving antenna comprising multiple satellite antenna elements that receive first and second polarized signals from said plurality of mobile terminals, wherein said first polarized signals correspond to a first one of said dual polarizations and said second polarized signals correspond to a second one of said dual polarizations;
a first transponder on board said satellite that processes said first polarized signals received from said mobile terminals to convert said first polarized signals to a first feeder link signal for transmission to said satellite ground station using a first feeder link polarization;
a second transponder on board said satellite that processes said second polarized signals received from said mobile terminals to convert said second polarized signals to a second feeder link signal for transmission to said satellite ground station using a second feeder link polarization;
a ground-station dual-polarization receiving antenna at said satellite ground station that receives said first and second feeder link signals, said ground-station dual polarization receiving antenna comprising multiple ground-station antenna elements that receive said first and second feeder link signals from said satellite;
a dual-channel receiver connected to said ground-station dual-polarization receiving antenna that amplifies, filters, downconverts, and digitizes the received first and second feeder link signals to produce numerical sample streams corresponding to said received first and second feeder link signals received at each of said multiple satellite antenna elements and each of said dual-polarizations; and
a diversity demodulator connected to said dual channel receiver that combines said numerical samples streams to reproduce information transmitted by said plurality of mobile terminals.
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Abstract
A satellite communications system uses multiple ground stations and one or more satellites for communicating between mobile subscribers and a land-based communications network, such as the PSTN or the Internet. Multiple ground stations geographically dispersed minimize toll charges incurred routing calls from a mobile subscriber through the land network by reducing the need for long-distance calling. Further, because each ground station communicates with a given satellite using the same frequency spectrum, the subscriber capacity of the system increases and/or bandwidth requirements for the communications link between ground stations and satellites may be reduced. The present system uses ground-based beamforming techniques enabling each satellite to transmit signals in multiple transmission beams, each beam supporting one or more mobile subscribers. Each beam may reuse the same frequency spectrum, thereby increasing the number of subscribers supported by each satellite. Multiple ground stations cooperatively relay signals through a given satellite in a manner complementary with ground-based beamforming.
92 Citations
35 Claims
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1. A communications satellite system for providing communications between a plurality of mobile terminals and a satellite ground station, said system comprising:
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at least one orbiting satellite comprising a satellite dual-polarization receiving antenna, said satellite dual-polarization receiving antenna comprising multiple satellite antenna elements that receive first and second polarized signals from said plurality of mobile terminals, wherein said first polarized signals correspond to a first one of said dual polarizations and said second polarized signals correspond to a second one of said dual polarizations;
a first transponder on board said satellite that processes said first polarized signals received from said mobile terminals to convert said first polarized signals to a first feeder link signal for transmission to said satellite ground station using a first feeder link polarization;
a second transponder on board said satellite that processes said second polarized signals received from said mobile terminals to convert said second polarized signals to a second feeder link signal for transmission to said satellite ground station using a second feeder link polarization;
a ground-station dual-polarization receiving antenna at said satellite ground station that receives said first and second feeder link signals, said ground-station dual polarization receiving antenna comprising multiple ground-station antenna elements that receive said first and second feeder link signals from said satellite;
a dual-channel receiver connected to said ground-station dual-polarization receiving antenna that amplifies, filters, downconverts, and digitizes the received first and second feeder link signals to produce numerical sample streams corresponding to said received first and second feeder link signals received at each of said multiple satellite antenna elements and each of said dual-polarizations; and
a diversity demodulator connected to said dual channel receiver that combines said numerical samples streams to reproduce information transmitted by said plurality of mobile terminals. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25)
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26. A communications satellite system for providing communications between a plurality of mobile terminals and a satellite ground station, said system comprising:
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at least two orbiting satellites each comprising a multi-element, dual-polarization receiving antenna comprising multiple satellite antenna elements that receive signals from said plurality of mobile terminals, each of said satellites having a dual-channel transponder that transponds signals received by each of said multiple satellite antenna elements so as to preserve relative phase and amplitude between signals from different satellite antenna elements of the same satellite;
at least one ground station comprising at least two receiving antennas each said receiving antenna being orientated toward a corresponding one of said at least two satellites to receive transponded signals transmitted from said corresponding satellite to said ground station;
a diversity receiver at said at least one ground station for jointly processing transponded signals transmitted from said at least two satellites and received by said at least two receiving antennas to decode information transmitted by said mobile communications terminals. - View Dependent Claims (27, 28, 29, 30, 31, 32, 33, 34, 35)
a plurality of demultiplexers for separating signals received from each satellite into separate signals corresponding to different satellite antenna elements; and
a plurality of channelizers for further separating each of said separated signals by frequency channel to obtain channelized signals.
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34. The system of claim 33 further comprising a plurality of beamformers for each of said frequency channels to combine ones of said channelized signals corresponding to the same frequency channel to obtain beamformed signals.
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35. The system of claim 34 further comprising a plurality of diversity demodulators for combining ones of said beamformed signals corresponding to the same frequency channel and beam direction but different satellites to decode information transmitted by said mobile communications terminals.
Specification