Interference cancellation methods and apparatus
Methods and apparatus for interference cancelation in a radio frequency communications device are described. In various embodiments a signal to be transmitted in converted into an optical signal and processed using an optical filter assembly including one or more optical filters to generate an optical interference cancelation signal. The optical interference cancelation signal is converted into an analog radio frequency interference cancelation signal using an optical to electrical converter prior to the analog radio frequency interference cancelation signal being combined with a received signal to cancel interference, e.g., self interference. The optical filter assembly can include a large number of taps, e.g., 30, 50, 100 or more. Each tap may be implemented as a separate optical filter or series of optical filters. Delays and/or gain of the optical filters can be controlled dynamically based on channel estimates which may change due to changes in the environment and/or communications device position.
1. A communications device comprising:
a radio frequency signal to optical signal converter comprising:
a radio frequency input; and
a first optical output;
an optical filter assembly comprising:
an optical input operably coupled to the first optical output;
an optical filter control signal input operative to receive a control signal comprising a calculated coefficient that defines an operation of the optical filter assembly; and
a second optical output; and
an optical to radio frequency converter comprising:
a second optical input operably coupled to the second optical output; and
a radio frequency output.
2. The communications device of claim 1 , wherein the optical to radio frequency converter comprises a photodetector.
3. The communications device of claim 2 , wherein the photodetector is a balanced photodetector.
4. The communications device of claim 1 , wherein calculated coefficient is a scalar value.
5. The communications device of claim 1 , wherein calculated coefficient is based, at least in part, on a channel-specific estimate of self-interference.
6. An interference cancelation method comprising: receiving a first radio frequency signal; generating a first optical signal based on a second frequency signal; optically filtering the first optical signal based on a calculated coefficient; optically attenuating the first optical signal to generate a second optical signal; and generating a radio frequency interference cancelation signal from the second optical signal.
7. The interference cancellation method of claim 6 , wherein generating the radio frequency interference cancelation signal is based on the second optical signal and a third optical signal.
8. The interference cancellation method of claim 7 , wherein the third optical signal is received from an optical filter assembly.
9. The interference cancellation method of claim 6 , further comprising:
combining the first radio frequency signal with the radio frequency interference cancellation signal to generate a third radio frequency signal.
10. The interference cancellation method of claim 9 , wherein combining the first radio frequency signal with the radio frequency interference cancellation signal is performed in a radio frequency domain.
11. The interference cancellation method of claim 6 , wherein the radio frequency interference cancelation signal comprises a delayed interference signal.
12. The interference cancellation method of claim 6 , wherein optically attenuating the first optical signal to generate the second optical signal is controlled by an optical filter control signal.
13. A non-transitory computer readable medium including computer executable instructions, which when executed by one or more processors, cause the one or more processors to perform the steps of:
controlling a radio frequency signal optical signal converter to generate a first optical signal responsive to receipt of a radio frequency signal;
controlling an optical filter assembly to attenuate the first optical signal to generate a second optical signal; and
controlling an optical to radio frequency converter coupled to an output of the optical filter assembly, to generate a radio frequency interference cancelation signal from second optical signal.
14. The non-transitory computer readable medium of claim 13 , wherein the radio frequency signal is a received radio frequency signal.
15. The non-transitory computer readable medium of claim 14 , wherein the radio frequency interference cancellation signal is based, at least in part, on a transmitted radio frequency signal.
16. The non-transitory computer readable medium of claim 15 , wherein the computer executable instructions, which when executed by the one or more processors, cause the one or more processors to control a signal combiner to combine the received radio frequency signal with the radio frequency interference cancelation signal to reduce interference by the transmitted radio frequency signal on the received radio frequency signal.
17. A communications device comprising:
a radio frequency signal to optical signal converter comprising:
a radio frequency input to receive a first radio frequency signal; and
a first optical output operative to provide a first optical signal corresponding to the radio frequency signal;
an optical filter assembly comprising:
an optical input coupled to the first optical output and operative to receive the first optical signal;
an optical filter control signal input operative to receive a control signal; and
a second optical output operative to provide a second optical signal based on the first optical signal and a calculated coefficient; and
an optical to radio frequency converter comprising:
a second optical input coupled to the second optical output and operative to receive the second optical signal; and
a radio frequency output providing a second radio frequency signal operative to cancel at least a portion of the first radio frequency signal.
18. The communications device of claim 17 , wherein the first radio frequency signal is a transmitted radio frequency signal transmitted by the communications device.
19. The communications device of claim 18 , wherein the second radio frequency signal is combined with a received radio frequency signal received by the communications device.
20. The communications device of claim 19 , wherein:
the transmitted radio frequency signal is transmitted by a first antenna; and
the received radio frequency signal is received by a second antenna different from the first antenna.
21. The communications device of claim 19 , comprising:
an antenna; wherein:
the transmitted radio frequency signal is transmitted by the antenna; and
the received radio frequency signal is received by the antenna simultaneously with the transmitted radio frequency signal being transmitted by the antenna.
22. The communications device of claim 18 , wherein the second radio frequency signal is based, at least in part, on a reflection of the transmitted radio frequency signal.