Satellite for end to end beamforming
Methods and systems are described for providing end-to-end beamforming. For example, end-to-end beamforming systems include end-to-end relays and ground networks to provide communications to user terminals located in user beam coverage areas. The ground segment can include geographically distributed access nodes and a central processing system. Return uplink signals, transmitted from the user terminals, have multipath induced by a plurality of receive/transmit signal paths in the end to end relay and are relayed to the ground network. The ground network, using beamformers, recovers user data streams transmitted by the user terminals from return downlink signals. The ground network, using beamformers generates forward uplink signals from appropriately weighted combinations of user data streams that, after relay by the end-end-end relay, produce forward downlink signals that combine to form user beams.
1. A satellite for providing communications between a plurality of access nodes (ANs) and a plurality of user terminals, the plurality of ANs geographically distributed over an AN coverage area and the plurality of user terminals geographically distributed over a user coverage area, the satellite comprising:
a feeder-link antenna subsystem to illuminate the access node (AN) coverage area, the feeder-link antenna subsystem comprising an array of cooperating feeder-link constituent transmit elements and an array of cooperating feeder-link constituent receive elements;
a user-link antenna subsystem to illuminate the user coverage area, the user-link antenna subsystem comprising an array of cooperating user-link constituent transmit elements and an array of cooperating user-link constituent receive elements;
a plurality of forward-link transponders, each coupled between a respective one of the feeder-link constituent receive elements and a respective one of the user-link constituent transmit elements; and
a plurality of return-link transponders, each coupled between a respective one of the user-link constituent receive elements and a respective one of the feeder-link constituent transmit elements.
2. The satellite of claim 1 , wherein the forward-link transponders and the return-link transponders are bent-pipe transponders.
3. The satellite of claim 1 , wherein the forward-link transponders are coupled with the respective feeder-link constituent receive elements so as to create forward downlink signals from received superpositions of a plurality of time-synchronized end-to-end beam-weighted forward uplink signals received from the plurality of ANs.
4. The satellite of claim 3 , wherein the plurality of forward downlink signals transmitted by the user-link constituent transmit elements spatially superpose to contribute to forming a plurality of forward beams in the user coverage area.
5. The satellite of claim 1 , wherein the return-link transponders are coupled with the respective user-link constituent receive elements so as to create return downlink signals from respective superpositions of return uplink signals received from at least some of the plurality of user terminals.
6. The satellite of claim 1 , wherein each forward-link transponder and each return-link transponder is a dual-pole transponder.
7. The satellite of claim 1 , wherein the feeder-link antenna subsystem differs from the user-link antenna subsystem in aperture size.
8. The satellite of claim 1 , wherein the feeder-link antenna subsystem and the user-link antenna subsystem operate in a same frequency band.
9. The satellite of claim 1 , wherein:
each forward-link transponder accepts an input at a first frequency band and outputs at a second frequency band;
each return-link transponder accepts an input at the second frequency band and outputs at the first frequency band.
10. The satellite of claim 1 , wherein the user coverage area differs from the AN coverage area.
11. The satellite of claim 1 , wherein the AN coverage area is a single contiguous coverage area.
12. The satellite of claim 1 , wherein the AN coverage area is a subset of the user coverage area.
13. The satellite of claim 1 , wherein the AN coverage area is less than one fifth the user coverage area in physical area.
14. The satellite of claim 1 , wherein:
the feeder-link antenna subsystem further comprises a feeder-link reflector; and
the user-link antenna subsystem further comprises a user-link reflector.
15. The satellite of claim 14 , wherein the physical area of the feeder-link reflector is at least five times the physical area of the user-link reflector.
16. The satellite of claim 1 , wherein the user-link antenna subsystem comprises a first user-link antenna subsystem having a corresponding first user coverage area and a second user-link antenna subsystem having a second user coverage area.
17. The satellite of claim 16 , wherein:
each forward-link transponder comprises a forward-link switch;
the forward-link switch couples a respective one of the feeder-link constituent receive elements with a respective one of the user-link constituent transmit elements of the first user-link antenna subsystem when the forward-link switch is in a first switch mode; and
the forward-link switch couples the respective one of the feeder-link constituent receive elements with a respective one of the user-link constituent transmit elements of the second user-link antenna subsystem when the forward-link switch is in a second switch mode.
18. The satellite of claim 16 , wherein:
each return-link transponder comprises a return-link switch;
each return-link switch couples a respective one of the user-link constituent receive elements of the first user-link antenna subsystem with a respective one of the feeder-link constituent transmit elements when the return-link switch is in a first switch mode; and
each return-link switch couples a respective one of the user-link constituent receive elements of the second user-link antenna subsystem with the respective one of the feeder-link constituent transmit elements when the return-link switch is in a second switch mode.
19. The satellite of claim 16 , wherein a first portion of the first user coverage area overlaps the second user coverage area, and a second portion of the first user coverage area does not overlap the second user coverage area.
20. The satellite of claim 16 , wherein the second user coverage area is a subset of the first user coverage area.
21. The satellite of claim 16 , wherein the first user coverage area is non-overlapping with the second user coverage area.
22. The satellite of claim 16 , wherein the plurality of user-link constituent transmit elements comprises a first plurality of constituent transmit elements to illuminate the first user coverage area and a second plurality of constituent transmit elements to illuminate the second user coverage area.
23. The satellite of claim 16 , wherein:
the first user-link antenna subsystem comprises a first user-link reflector to illuminate the first user coverage area; and
the second user-link antenna subsystem comprises a second user-link reflector to illuminate the second user coverage area.
24. The satellite of claim 23 , wherein the first user-link reflector and the second user-link reflector are of approximately a same physical area.
25. The satellite of claim 23 , wherein:
each forward-link transponder has a transmit side selectively coupled with first and second respective ones of the user-link transmit feeds, each first respective user-link transmit feed positioned to illuminate the first user-link reflector, and each second respective user-link transmit feed positioned to illuminate the second user-link reflector; and
each return-link transponder has a receive side selectively coupled with first and second respective ones of the user-link receive feeds, each first respective user-link receive feed positioned to illuminate the first user-link reflector, and each second respective user-link receive feed positioned to illuminate the second user-link reflector.
26. The satellite of claim 1 , wherein:
the feeder-link reflector is a first feeder-link reflector;
the AN coverage area is a first AN coverage area;
the feeder-link antenna subsystem further comprises a second feeder-link reflector to illuminate a second AN coverage area; and
wherein a first portion of the plurality of ANs is geographically distributed over the first AN coverage area and a second portion of the plurality of ANs is geographically distributed over the second AN coverage area.
27. The satellite of claim 1 , wherein the feeder-link constituent receive elements and the feeder link transmit elements are implemented as full-duplex antenna elements.
28. The satellite of claim 1 , wherein the user link constituent receive elements and the user link constituent transmit elements are implemented as full-duplex antenna elements.
29. The satellite of claim 1 , wherein the user-link antenna subsystem further comprises a user-link receive array antenna and a user-link transmit array antenna.
30. The satellite of claim 29 , wherein:
the plurality of user-link constituent receive elements are associated with a user-link receive reflector with a first frequency range;
the plurality of user-link constituent transmit elements illuminates a user-link transmit reflector with a second frequency range; and
the user-link receive reflector and the user-link transmit reflector are each sized to illuminate a same user coverage area with the first and second frequency ranges, respectively.
31. The satellite of claim 1 , further comprising a beacon generator.