Method and apparatus for combining transponders on multiple satellites into virtual channels

• US 20030031265A1
• Filed: 10/08/2002
• Published: 02/13/2003
• Est. Priority Date: 02/04/1998
• Status: Active Grant

• Current Assignee: Virlite Communication LLC (Intellectual Ventures LLC)
• Original Assignee: Virtual Satellite Corporation
• Inventors: Friedman, Robert F.
• Granted Patent: US 7,039,119 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04B 7/18513 Transmission in a satellite or space-based system
• CPC Class Codes: H04B 7/18515 Transmission equipment in satellites or space-based relays

Abstract

A satellite communications system provides an information channel between remotely located transmitters and receivers. A virtual satellite system provides the same service, but divides the signal either in power or in data content into subchannels such that any particular signal is conducted to the intended receiver via a plurality of traditional satellite channels. The receiving terminal accepts the plurality of signals simultaneously from a possible plurality of satellites, combining the subchannels comprising the virtual channel into the original signal content as if conducted via a single channel. The receiving antenna system receives satellite subchannel signals from a plurality of directions using multiple antennas or a single antenna with multi-direction capability. Prior to signal combining, the receiver necessarily time-synchronizes the plurality of subchannels by introducing time delay in some channels before combining the subsignals into the original composite. A timing signal present in the virtual satellite system assists the receiver in determining the amount of delay to apply to each incoming signal. The timing signal is either a separate carrier or an additional modulation on the existing information-bearing carrier.

Claims

1. A satellite communications system which provides an enhanced digital communication channel, the satellite communications system comprising:

a multi-channel uplink system dividing the original signal into a plurality of subchannels and adding a common timing signal to each subchannel, the multi-channel uplink system comprising;

a subchannel divider for transforming the original digital signal into a plurality of digital subchannels such that each digital subchannel signal contains at least some information unique to that subchannel and also such that the bit rate of each digital subchannel signal is lower than the bit rate of the original digital signal;

a timing generator creating a periodic signal,

signal combining means coupled to the timing generator output and the subchannel divider output associated with each subchannel for adding the common timing signal to each subchannel information signal and within the bandwidth of each subchannel information signal such that no additional bandwidth allocation is required to transmit the timing information signal;

upconverting means coupled to the signal combining means output associated with each subchannel for translating the frequency of the timing-added subchannel signal to the frequency of the selected satellite transponder;

amplifier means coupled to the upconverting means output associated with each subchannel for increasing the power of the translated, timing-added subchannel signal; and

antenna means coupled to the amplifier means output associated with each subchannel directing a radio frequency wave toward the receiving antenna of the satellite containing the transponder selected for the associated subchannel; and

a receiving terminal system collecting signals from a plurality of selected satellite transponders and creating a delayed reconstruction of the original signal, the receiving terminal system comprising;

a multiple beam antenna simultaneously receiving signals from the plurality of transponders and presenting each of said signals on a separate output port;

a tuner coupled to each multiple beam antenna output port for translating the frequency of each received signal to a fixed intermediate frequency;

a demodulator coupled to each tuner output for demodulating tuner output and creating a bit stream corresponding to the information content of the associated subchannel;

delay means coupled to each demodulator output for delaying first-arriving subchannel signals such that outputs of the plurality of delay means are synchronized in time;

a digital combiner coupled to the output of the plurality of delay means for combining the information in each of the subchannels into a delayed reconstruction of the original digital signal;

a timing signal correlator coupled to each tuner output for measuring the relative delay between arriving subchannel signals;

a nonvolatile memory for storing information about the frequency and propagation delay properties of the virtual channels to be selected; and

controller coupled to the multiple beam antenna, the plurality of tuners, the plurality of delay means, the timing signal correlator, and the nonvolatile memory for receiving signals from the timing signal correlator and the nonvolatile memory and issuing control signals to the multiple beam antenna setting beam direction and polarization, control signals to the tuners to set subchannel receive frequencies, and control signals to the plurality of delay means to synchronize delay means outputs.

2. The satellite communications system of claim 1 wherein at least some of the transponders associated with the plurality of subchannels are located on the same satellite.

3. The satellite communications system of claim 1 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

4. The satellite communications system of claim 2 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

5. The satellite communications system of claim 1 wherein the timing signal associated with any particular subchannel is transmitted in a separate frequency allocation but on the same satellite as the information-bearing carrier, requiring the controller to firstly direct the tuners to receive the frequency-separated timing signal to measure relative propagation delay of the subchannels, secondly set the amount of delay in the plurality of delay means in accord with the relative propagation delays measured in the first step, and thirdly redirect the tuners to receive the associated information-bearing subchannels.

6. The satellite communications system of claim 5 wherein at least some of the transponders associated with the plurality of subchannels are located on the same satellite.

7. The satellite communications system of claim 5 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

8. The satellite communications system of claim 6 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

9. A satellite communications system which provides an enhanced digital communication channel, the satellite communications system comprising:

a multi-channel uplink system dividing the original signal into a plurality of subchannels and adding a common timing signal to each subchannel, the multi-channel uplink system comprising;

a subchannel divider for transforming the original digital signal into a plurality of digital subchannels such that each digital subchannel signal carries identical information at the same bit rate as the original digital signal;

a timing generator creating a periodic signal,

signal combining means coupled to the timing generator output and the subchannel divider output associated with each subchannel for adding the common timing signal to each subchannel information signal and within the bandwidth of each subchannel information signal such that no additional bandwidth allocation is required to transmit the timing information signal;

upconverting means coupled to the signal combining means output associated with each subchannel for translating the frequency of the timing-added subchannel signal to the frequency of the selected satellite transponder;

amplifier means coupled to the upconverting means output associated with each subchannel for increasing the power of the translated, timing-added subchannel signal; and

antenna means coupled to the amplifier means output associated with each subchannel directing a radio frequency wave toward the receiving antenna of the satellite containing the transponder selected for the associated subchannel; and

a receiving terminal system collecting signals from a plurality of selected satellite transponders and creating a delayed reconstruction of the original signal, the receiving terminal system comprising;

a multiple beam antenna simultaneously receiving signals from the plurality of transponders and presenting each of said signals on a separate output port;

a tuner coupled to each multiple beam antenna output port for translating the frequency of each received signal to a fixed intermediate frequency;

a demodulator coupled to each tuner output for demodulating tuner output and creating a stream of soft decisions in the form of digitized decision-confidence-values corresponding to the associated subchannel;

delay means coupled to each demodulator output for delaying first-arriving subchannel signals such that soft decision outputs of the plurality of delay means are synchronized in time;

a digital combiner coupled to the output of the plurality of delay means for combining soft decision from all subchannels received into a delayed reconstruction of the original digital signal;

a timing signal correlator coupled to each tuner output for measuring the relative delay between arriving subchannel signals;

a digital correlator coupled to the delay means outputs for providing an additional measure of the relative delay between channels;

a nonvolatile memory for storing information about the frequency and propagation delay properties of the virtual channels to be selected; and

a controller coupled to the multiple beam antenna, the plurality of tuners, the plurality of delay means, the timing signal correlator, the digital correlator, and the nonvolatile memory for receiving signals from the timing signal correlator and the nonvolatile memory and issuing control signals to the multiple beam antenna setting beam direction and polarization, control signals to the tuners to set subchannel receive frequencies, and control signals to the plurality of delay means to synchronize delay means outputs.

10. The satellite communications system of claim 9 wherein there is no digital correlator.

11. The satellite communications system of claim 9 wherein at least some of the transponders associated with the plurality of subchannels are located on the same satellite.

12. The satellite communications system of claim 9 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

13. The satellite communications system of claim 11 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

14. The satellite communications system of claim 9 wherein the timing signal associated with any particular subchannel is transmitted in a separate frequency allocation but on the same satellite as the information-bearing carrier, requiring the controller to firstly direct the tuners to receive the frequency-separated timing signal to measure relative propagation delay of the subchannels, secondly set the amount of delay in the plurality of delay means in accord with the relative propagation delays measured in the first step, and thirdly redirect the tuners to receive the associated information-bearing subchannels.

15. The satellite communications system of claim 14 wherein at least some of the transponders associated with the plurality of subchannels are located on the same satellite.

16. The satellite communications system of claim 14 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

17. The satellite communications system of claim 15 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

18. A satellite communications system which provides an enhanced analog communication channel, the satellite communications system comprising:

a multi-channel uplink system dividing the original signal into a plurality of subchannels and adding a common timing signal to each subchannel, the multi-channel uplink system comprising;

a subchannel divider for transforming the original analog signal into a plurality of analog subchannels such that each subchannel signal contains at least some information unique to that subchannel;

a timing generator creating a periodic signal,

signal combining means coupled to the timing generator output and the subchannel divider output associated with each subchannel for adding the common timing signal to each subchannel information signal and within the bandwidth of each subchannel information signal such that no additional bandwidth allocation is required to transmit the timing information signal;

upconverting means coupled to the signal combining means output associated with each subchannel for translating the frequency of the timing-added subchannel signal to the frequency of the selected satellite transponder;

amplifier means coupled to the upconverting means output associated with each subchannel for increasing the power of the translated, timing-added subchannel signal; and

antenna means coupled to the amplifier means output associated with each subchannel directing a radio frequency wave toward the receiving antenna of the satellite containing the transponder selected for the associated subchannel; and

a receiving terminal system collecting signals from a plurality of selected satellite transponders and creating a delayed reconstruction of the original signal, the receiving terminal system comprising;

a multiple beam antenna simultaneously receiving signals from the plurality of transponders and presenting each of said signals on a separate output port;

a tuner coupled to each multiple beam antenna output port for translating the frequency of each received signal to a fixed intermediate frequency;

a demodulator coupled to each tuner output for demodulating tuner output and creating an analog signal corresponding to the information content of the associated subchannel;

delay means coupled to each demodulator output for delaying first-arriving subchannel signals such that outputs of the plurality of delay means are synchronized in time;

an analog combiner coupled to the output of the plurality of delay means for combining the information in each of the subchannels into a delayed reconstruction of the original analog signal;

a timing signal correlator coupled to each tuner output for measuring the relative delay between arriving subchannel signals;

a nonvolatile memory for storing information about the frequency and propagation delay properties of the virtual channels to be selected; and

a controller coupled to the multiple beam antenna, the plurality of tuners, the plurality of delay means, the timing signal correlator, and the nonvolatile memory for receiving signals from the timing signal correlator and the nonvolatile memory and issuing control signals to the multiple beam antenna setting beam direction and polarization, control signals to the tuners to set subchannel receive frequencies, and control signals to the plurality of delay means to synchronize delay means outputs.

19. The satellite communications system of claim 18 wherein the analog combiner provides additional relative subchannel delay information to the controller.

20. The satellite communications system of claim 18 wherein at least some of the transponders associated with the plurality of subchannels are located on the same satellite.

21. The satellite communications system of claim 18 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

22. The satellite communications system of claim 20 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

23. The satellite communications system of claim 18 wherein the timing signal associated with any particular subchannel is transmitted in a separate frequency allocation but on the same satellite as the information-bearing carrier, requiring the controller to firstly direct the tuners to receive the frequency-separated timing signal to measure relative propagation delay of the subchannels, secondly set the amount of delay in the plurality of delay means in accord with the relative propagation delays measured in the first step, and thirdly redirect the tuners to receive the associated information-bearing subchannels.

24. The satellite communications system of claim 23 wherein at least some of the transponders associated with the plurality of subchannels are located on the same satellite.

25. The satellite communications system of claim 23 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

26. The satellite communications system of claim 24 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

27. The satellite communications system of claim 18 wherein the plurality of subchannels contain identical information, the associated carriers being modulated identically.

28. The satellite communications system of claim 27 wherein the analog combiner provides additional relative subchannel delay information to the controller.

29. The satellite communications system of claim 27 wherein at least some of the transponders associated with the plurality of subchannels are located on the same satellite.

30. The satellite communications system of claim 27 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

31. The satellite communications system of claim 29 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

32. The satellite communications system of claim 27 wherein the timing signal associated with any particular subchannel is transmitted in a separate frequency allocation but on the same satellite as the information-bearing carrier, requiring the controller to firstly direct the tuners to receive the frequency-separated timing signal to measure relative propagation delay of the subchannels, secondly set the amount of delay in the plurality of delay means in accord with the relative propagation delays measured in the first step, and thirdly redirect the tuners to receive the associated information-bearing subchannels.

33. The satellite communications system of claim 32 wherein at least some of the transponders associated with the plurality of subchannels are located on the same satellite.

34. The satellite communications system of claim 32 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.

35. The satellite communications system of claim 33 wherein the multiple beam antenna is replaced with multiple independent single beam antennas.