Method and apparatus for relayed communication using band-pass signals for self-interference cancellation

• US 20030031279A1
• Filed: 08/08/2001
• Published: 02/13/2003
• Est. Priority Date: 08/08/2001
• Status: Active Grant

• Current Assignee: ViaSat Incorporated
• Original Assignee: ViaSat Incorporated
• Inventors: Murphy, James, Miller, Mark, Blount, Richard
• Granted Patent: US 6,907,093 B2
• Time in Patent Office: Days
• US Class Current: 375/346
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 7/15585 by interference cancellation
• CPC Class Codes: H04B 7/2606 Arrangements for base station coverage control, e.g. by using relays in tunnels

Abstract

Self-interference cancellation is provided in two-way relayed electromagnetic communication between a first device and a second device through a relay station wherein a representation of a relayed composite signal above baseband and a representation of a locally modulated interface signal above baseband interact to effect the self-interference cancellation. Specifically, the composite signal, which contains a relayed version of the locally modulated (near) signal from the first device and a relayed version of a modulated far signal from the second device, is received at the first device from the relay station. The composite signal is then provided in a representation as a first interface signal at a first frequency at or above baseband to a canceler module of the first device and a representation of the modulated near signal at a second frequency above baseband is provided as a second interface signal to the canceler module. Part of the relayed version of the modulated near signal is canceled from the representation of the composite signal using the representation of the modulated near signal as provided to the canceler module to produce a third interface signal as output at a third frequency at or above baseband. The first and second frequencies may or may not be the same.

Claims

1. A method for providing self-interference cancellation in two-way relayed electromagnetic communication between a first device and a second device through a relay station comprising the steps of:

generating at said first device a modulated near signal;

transmitting said modulated near signal from said first device to said relay station;

receiving at said first device a composite signal from said relay station, said composite signal containing a relayed version of said modulated near signal and a relayed version of a modulated far signal transmitted from said second device;

providing said composite signal in a representation as a first interface signal to a canceler module of said first device;

providing a representation of said modulated near signal as a second interface signal to said canceler module, said second interface signal being of a frequency centered at or near a second interface frequency not at baseband;

canceling at said canceler module a portion of said relayed version of said modulated near signal from said representation of said composite signal using said second interface signal to a produce a cancellation-processed signal; and

outputting said cancellation-processed signal as a third interface signal from said canceler module.

2. The method of claim 1 wherein said first interface signal is of a frequency centered at or near a first interface frequency not at baseband.

3. The method of claim 2 wherein said first interface frequency is an Intermediate Frequency (IF) or a Radio Frequency (RF) frequency.

4. The method of claim 1 wherein said second interface signal is an IF or RF frequency.

5. The method of claim 1 wherein said third interface signal is of a frequency centered at or near a third interface frequency not at baseband.

6. The method of claim 5 wherein said third interface frequency is an IF or RF frequency.

7. The method according to claim 1 wherein said first, second and third interface signals are provided or outputted at readily accessible locations.

8. The method according to claim 1 wherein said second interface signal is provided from a point in its signal path immediately preceding a signal emission stage.

9. The method according to claim 1 wherein said canceling step includes:

applying a time delay and phase rotation to a representation of said second interface signal to obtain a time-delayed and phase-rotated local near signal;

correlating said time-delayed and phase-rotated local near signal with at least a representation of said first interface signal to obtain correction signals for said time-delayed and phase-rotated local near signal;

adaptively filtering said time-delayed and phase-rotated local near signal to produce a filtered signal; and

applying said filtered signal with said at least said representation of said composite signal to yield said cancellation-processed signal.

10. The method according to claim 9 wherein said canceling step includes:

downconverting said first interface signal to produce said representation of said first interface signal;

downconverting said second interface signal to produce said representation of said second interface signal; and

upconverting said cancellation-processed signal to produce said third interface signal.

11. A method for retrofitting a first device for self-interference cancellation capability in two-way relayed electromagnetic communication between said first device and a second device through a relay station, said first device having an existing modulator unit, an existing transmitter equipment, an existing receiver equipment and an existing demodulator unit, said method comprising the steps of:

providing a composite signal in a representation as a first interface signal from said receiver equipment to a canceler module of said first device, said composite signal containing a relayed version of a modulated near signal transmitted from said first device and a relayed version of a modulated far signal transmitted from said second device;

providing a representation of said modulated near signal as a second interface signal from said modulator unit to said canceler module, said second interface signal also provided to said transmitter equipment, said second interface signal being of a frequency centered at or near a second interface frequency not at baseband;

canceling at said canceler module a portion of said relayed version of said modulated near signal from said representation of said composite signal using said second interface signal to produce a cancellation-processed signal; and

outputting said cancellation-processed signal as a third interface signal from said canceler module to said receiver equipment.

12. The method of claim 11 wherein said transmitter equipment includes an upconverter, a downconverter, or a mixer.

13. The method of claim 11 wherein said transmitter equipment includes an amplifier.

14. The method of claim 13 wherein said amplifier is a high power amplifier (HPA).

15. The method of claim 11 wherein said transmitter equipment includes an antenna.

16. The method of claim 11 wherein said transmitter equipment includes a splitter, combiner, or splitter/combiner.

17. The method of claim 11 wherein said receiver equipment includes an upconverter, a downconverter, or a mixer.

18. The method of claim 11 wherein said receiver equipment includes an amplifier.

19. The method of claim 18 wherein said amplifier is a low noise amplifier (LNA).

20. The method of claim 11 wherein said receiver equipment includes an antenna.

21. The method of claim 11 wherein said receiver equipment includes a splitter, combiner, or splitter/combiner.

22. The method of claim 11 wherein said first interface signal is of a frequency centered at or near a first interface frequency.

23. The method of claim of claim 22 wherein said first interface frequency is an Intermediate Frequency (IF) or a Radio Frequency (RF).

24. The method of claim 11 wherein said second interface frequency is an IF or RF frequency.

25. The method of claim 11 wherein said third interface signal is of a frequency centered at or near a third interface frequency.

26. The method of claim of claim 25 wherein said third interface frequency is an IF or RF frequency.

27. The method according to claim 11 wherein said first, second and third interface signals are provided or outputted at readily accessible locations.

28. The method according to claim 11 wherein said second interface signal is provided from a point in its signal path immediately preceding a signal emission stage.

29. The method according to claim 11 wherein said canceling step includes:

applying a time delay and phase rotation to a representation of said second interface signal to obtain a time-delayed and phase-rotated local near signal;

correlating said time-delayed and phase-rotated local near signal with at least a representation of said first interface signal to obtain correction signals for said time-delayed and phase-rotated local near signal;

adaptively filtering said time-delayed and phase-rotated local near signal to produce a filtered signal; and

applying said filtered signal with said at least said representation of said composite signal to yield said cancellation-processed signal.

30. The method according to claim 29 wherein said canceling step includes:

downconverting said first interface signal to produce said representation of said first interface signal;

downconverting said second interface signal to produce said representation of said second interface signal; and

upconverting said cancellation-processed signal to produce said third interface signal.

31. A method for providing self-interference cancellation in two-way relayed electromagnetic communication between a first device and a second device through a relay station comprising the steps of:

generating at said first device a modulated near signal;

transmitting said modulated near signal from said first device to said relay station;

receiving at said first device a composite signal from said relay station, said composite signal containing a relayed version of said modulated near signal and a relayed version of a modulated far signal transmitted from said second device;

providing said composite signal in a representation as a first interface signal to a canceler module of said first device;

providing a representation of said modulated near signal as a second interface signal to said canceler module, said second interface signal being of a frequency centered at or near a second interface frequency not at baseband;

canceling at said canceler module a portion of said relayed version of said modulated near signal from said representation of said composite signal using said second interface signal to a produce a cancellation-processed signal;

demodulating said cancellation-processed signal to produce at least one demodulated signal; and

outputting said at least one demodulated signal from said canceler module.

32. The method of claim 31 wherein said step demodulating step produces more than one demodulated signal using more than one demodulator.

33. A system for providing self-interference cancellation in two-way relayed electromagnetic communication between a first device and a second device through a relay station comprising:

means for generating at said first device a modulated near signal;

means for transmitting said modulated near signal from said first device to said relay station;

means for receiving at said first device a composite signal from said relay station, said composite signal containing a relayed version of said modulated near signal and a relayed version of a modulated far signal transmitted from said second device;

means for providing said composite signal in a representation as a first interface signal to a canceler module of said first device;

means for providing a representation of said modulated near signal as a second interface signal to said canceler module, said second interface signal being of a frequency centered at or near a second interface frequency not at baseband;

means for canceling at said canceler module a portion of said relayed version of said modulated near signal from said representation of said composite signal using said second interface signal to a produce a cancellation-processed signal; and

means for outputting said cancellation-processed signal as a third interface signal from said canceler module.