Pilot-based analog active interference canceller

1. A method for interference cancellation, comprising:

upconverting a waveform to a transmit frequency by mixing the waveform with a transmit local oscillator (LO) signal generated by a transmit LO, to generate an offending signal;

transmitting the offending signal from the transmitter;

receiving the offending signal at a receiver;

downconverting the offending signal by mixing the offending signal with a receive local oscillator (LO) signal generated by a receive LO;

injecting the receive LO signal into a transmit chain of the transmitter to create a transmit pilot within the offending signal, the transmit pilot being distinct from the transmit LO signal; and

determining a set of coefficients for the interference cancellation based on an output signal from the receiver.

2. The method of claim 1 , further comprising:

applying the set of coefficients to an adaptive filter coupled to the receiver; and

cancelling interference associated with the offending signal utilizing the adaptive filter with the applied set of coefficients.

3. The method of claim 2 , wherein the adaptive filter is a single tap minimum mean square error (MMSE) filter.

4. The method of claim 1 , further comprising utilizing a least mean square (LMS) error criterion for the determining the set of coefficients for the interference cancellation.

5. The method of claim 1 , further comprising:

enabling a path for the injecting the receive LO signal into the transmit chain if a first signal level of a desired receive signal is greater than a second signal level of the offending signal minus a threshold.

6. The method of claim 5 , wherein the threshold is between 8 dB and 12 dB.

7. The method of claim 5 , further comprising enabling the path for injecting the transmit pilot utilizing a switch.

8. The method of claim 1 , further comprising setting the receive LO to the transmit frequency of the offending signal, such that the transmit pilot enables interference cancellation of the offending signal at a fundamental frequency of the offending signal.

9. The method of claim 1 , wherein the transmitter operates at a Long Term Evolution (LTE) band and the receiver operates at a WiFi band.

10. The method of claim 1 , wherein the receiver and the transmitter share a same antenna.

11. The apparatus of claim 1 , wherein the transmitter operates at a Long Term Evolution (LTE) band and the receiver operates at a WiFi band.

12. An apparatus for interference cancellation, comprising:

a transmitter comprising a transmit local oscillator (LO) for generating a transmit LO signal and a transmit mixer for mixing a waveform with the transmit LO signal to generate an offending signal, the transmitter configured to transmit an offending signal;

a receiver comprising a receive LO for generating a receive LO signal and a receive mixer for mixing a received signal with the receive LO signal;

a splitter coupled to the receive LO for injecting the receive LO signal into a transmit chain of the transmitter to create a transmit pilot within the offending signal, the transmit pilot being distinct from the transmit LO signal; and

a processor coupled to the receiver for determining a set of coefficients for the interference cancellation based on an output signal from the receiver.

13. The apparatus of claim 12 , further comprising:

a coefficient control logic for applying the set of coefficients to an adaptive filter coupled to the receiver; and

a subtractor for cancelling interference associated with the offending signal with a filtered control signal outputted from the adaptive filter with the applied set of coefficients.

14. The apparatus of claim 13 , wherein the adaptive filter is a single tap minimum mean square error (MMSE) filter.

15. The apparatus of claim 12 , wherein the processor, being configured for determining the set of coefficients, is further configured to utilize a least mean square (LMS) error criterion for determining the set of coefficients for the interference cancellation.

16. The apparatus of claim 12 , further comprising:

a switch coupled to the processor for enabling a path between the splitter and the transmit chain for injecting the transmit pilot into the transmit chain if a first signal level of a desired receive signal is greater than a second signal level of the offending signal minus a threshold.

17. The apparatus of claim 16 , wherein the threshold is between 8 dB to 12 dB.

18. The apparatus of claim 12 , further comprising a second processor for setting the receive LO to the transmit frequency of the offending signal, such that the transmit pilot enables interference cancellation of the offending signal at a fundamental frequency of the offending signal.

19. The apparatus of claim 12 , further comprising an antenna;

wherein the receiver and the transmitter share the antenna.

20. An apparatus for interference cancellation, comprising:

means for upconverting a waveform to a transmit frequency by mixing the waveform with a transmit local oscillator (LO) signal generated by a means for generating the transmit LO signal, to generate an offending signal;

means for transmitting the offending signal;

means for receiving the offending signal;

means for downconverting the offending signal by mixing the offending signal with a receive local oscillator (LO) signal generated by a means for generating the receive LO signal;

means for injecting the receive LO signal into a transmit chain of the means for transmitting, to create a transmit pilot within the offending signal, the transmit pilot being distinct from the transmit LO signal; and

means for determining a set of coefficients for the interference cancellation based on an output signal from the means for receiving.

21. The apparatus of claim 20 , further comprising:

means for applying the set of coefficients to a means for adaptive filtering, wherein the means for adaptive filtering is coupled to the means for receiving; and

means for cancelling interference associated with the interference signal utilizing the means for adaptive filtering with the applied second set of coefficients.

22. A non-transitory computer-readable storage medium storing computer executable code, operable on a wireless communication device, the computer executable code comprising:

instructions for causing the wireless communication device to upconvert a waveform to a transmit frequency by mixing the waveform with a transmit local oscillator (LO) signal generated by a transmit LO, to generate an offending signal;

instructions for causing the wireless communication device to transmit the offending signal from the transmitter,

instructions for causing the wireless communication device to receive the offending signal at a receiver;

instructions for causing the wireless communication device to downconvert the offending signal by mixing the offending signal with a receive local oscillator (LO) signal generated by a receive LO;

instructions for causing the wireless communication device to inject the receive LO signal into a transmit chain of the transmitter to create a transmit pilot within the offending signal, the transmit pilot being distinct from the transmit LO signal; and

instructions for causing the wireless communication device to determine a set of coefficients for interference cancellation of the offending signal based on an output signal from the receiver.

23. The non-transitory computer-readable storage medium of claim 22 , wherein the computer executable code further comprises:

instructions for causing the wireless communication device to apply the set of coefficients to an adaptive filter coupled to the receiver; and

instructions for causing the wireless communication device to cancel interference associated with the offending signal utilizing the adaptive filter with the applied second set of coefficients.