Pilot-based analog active interference canceller

• US 9,800,287 B2
• Filed: 05/22/2015
• Issued: 10/24/2017
• Est. Priority Date: 05/22/2015
• Status: Expired due to Fees

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Hwang, Insoo, Nguyen, Cong, Song, Bongyong
• Primary Examiner(s): HUANG, WEN WU
• Application Number:
  US14/720,534
• Publication Number:
  US 20160344432A1
• Time in Patent Office: 886 Days
• Field of Search: 455 78, 455 82, 455 83
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver

Abstract

Aspects of the disclosure are directed to interference cancellation. A method for performing interference cancellation in a wireless communications device having a transmitter, a receiver, a coefficient controller, an analog interference cancellation (AIC) circuit and a receive local oscillator (LO) includes utilizing a receive local oscillator (LO) to generate a transmit pilot; injecting the transmit pilot into a transmit chain for transmission; utilizing a receiver to receive a signal, wherein the signal includes the transmit pilot and an interference signal; and determining a set of coefficients for the interference cancellation based on an output signal from the receiver.

Claims

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.