METHOD AND APPARATUS FOR THE CANCELLATION OF INTERMODULATION AND HARMONIC DISTORTION IN A BASEBAND RECEIVER

• US 20140161159A1
• Filed: 12/12/2012
• Published: 06/12/2014
• Est. Priority Date: 12/12/2012
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola Mobility LLC (Lenovo Group Ltd.)
• Inventors: Black, Gregory R., Schwent, Dale G.
• Granted Patent: US 8,917,792 B2
• Time in Patent Office: Days
• US Class Current: 375/219
• CPC Class Codes: H04B 1/0475 with means for limiting noise, interference or distortion H04B1/0483 takes precedence
• CPC Class Codes: H04B 1/109 by improving strong signal performance of the receiver when strong unwanted signals are present at the receiver input
• CPC Class Codes: H04B 1/123 using adaptive balancing or compensation means adaptive filter circuits and algorithms H03H
• CPC Class Codes: H04B 1/525 with means for reducing leakage of transmitter signal into the receiver
• CPC Class Codes: H04B 15/00 Suppression or limitation of noise or interference by means associated with receiver H04B1/10

Abstract

A method (600) and apparatus (200) cancel odd-order distortion signals. Desensitization can be determined (610) in a received signal caused by odd-order harmonic distortion occurring from at least one transmit signal. A baseband replica harmonic distortion signal can be generated (620) using the transmit signal. The baseband replica harmonic distortion signal can be converted (630) to a low frequency harmonic distortion signal. The low frequency harmonic distortion signal can be subtracted (640) from the received signal to cancel the odd-order distortion from the received signal to create a corrected signal.

Claims

1. A method comprising:

determining desensitization in a received signal caused by odd-order intermodulation distortion occurring from at least two transmit signals;

generating a baseband replica intermodulation distortion signal using the transmit signals;

converting the baseband replica intermodulation distortion signal to a low frequency intermodulation distortion signal, and

subtracting the low frequency intermodulation distortion signal from the received signal to cancel odd-order intermodulation distortion from the received signal to create a corrected signal.

2. The method of claim 1 further comprising filtering the low frequency distortion signal using a low pass filter where the low pass filter has a function similar to a low pass filter of a receiver receiving the received signal.

3. The method of claim 1,

wherein the odd-order intermodulation distortion includes at least one of an upper order and a lower order distortion signal, and

wherein the at least one of an upper order and a lower order distortion signal is determined based on frequencies of the transmit signals.

4. The method of claim 3, wherein the upper order frequency of the odd-order intermodulation distortion is determined by a function subtracting a higher frequency of the transmit signals form a lower frequency of the transmit signals and the lower order frequency of the odd-order intermodulation distortion is determined by a function subtracting the lower frequency of the transmit signal from the higher frequency of the transmit signals.

5. The method of claim 1 further comprising sampling the transmit signals near a Nyquist limit of the transmit signals to avoid aliasing where the sampling is performed prior to generating the baseband replica intermodulation distortion signal.

6. The method of claim 1, wherein generating the baseband replica intermodulation distortion signal comprises generating the baseband replica intermodulation distortion signal using interpolated complex signals.

7. The method of claim 1, wherein generating the baseband replica intermodulation distortion signal comprises generating the baseband replica intermodulation distortion signal using complex multiplication of a direct current baseband replica signal and an intermediate frequency signal having frequency that is the difference between a frequency of a local oscillator and a frequency of the odd order distortion.

8. The method of claim 1, wherein generating the baseband replica intermodulation distortion signal comprises generating the baseband replica intermodulation distortion signal using the frequency separation of the transmit signals.

9. The method of claim 1 wherein generating the baseband replica intermodulation distortion signal comprises determining one of a lower order demodulation signal using a function of an upper frequency intermodulation distortion signal multiplied by a function of a lower frequency intermodulation distortion signal, and an upper order demodulation signal using a function of the lower frequency intermodulation distortion signal multiplied by a function of the upper frequency intermodulation distortion signal.

10. The method of claim 1 further comprising scaling the generated baseband replica intermodulation distortion signal according to an expected distortion level using a function of a power level of the transmit signals and a gain of a receiver.

11. The method of claim 1 wherein a low frequency of the baseband replica intermodulation distortion signal is centered on direct current.

12. The method of claim 1 further comprising converting the baseband replica distortion signal to a low frequency replica distortion signal using complex multiplication on the baseband distortion signal and a clock signal having a frequency of a desired frequency.

13. An apparatus comprising:

a first receiver that receives a received signal;

a first transmitter that sends transmit signals, where the first transmitter causes odd-order distortion of the received signal; and

an adaptive baseband distortion canceller coupled between the receiver and the transmitter where the adaptive baseband distortion canceller generates a baseband replica distortion signal using transmit signals to be sent by the first transmitter, converts the baseband replica distortion signal to a low frequency distortion signal, and subtracts the low frequency distortion signal from the received signal to cancel the odd-order distortion from the received signal to create a corrected signal.

14. The apparatus of claim 13, wherein the adaptive baseband distortion canceller comprises a complex digital mixer that performs complex multiplication on the baseband replica distortion signal using a difference of the frequencies in the transmit signals.

15. The apparatus of claim 14, wherein the complex digital mixer has an input of the difference between a frequency of a local oscillator and a frequency of the odd-order distortion.

16. The apparatus of claim 13, wherein the adaptive intermodulation distortion canceller comprises a baseband distortion calculator.

17. The apparatus of claim 13, wherein the adaptive baseband distortion canceller comprises at least one of a least mean squared adaptive filter and correlation block to provide a desired signal amplitude and phase of the cancelling signal.

18. The apparatus of claim 13,

wherein the first transmitter sends first transmit signals,

wherein the apparatus further comprises a second transmitter that sends second transmit signals, and

wherein transmitting both the first transmit signals and the second transmit signals causes odd-order distortion of the received signal.

19. The apparatus of claim 13, further comprising a second receiver,

wherein the first transmitter causes odd-order distortion of the received signal by causing desensitization of a receive channel frequency when transmitting on a frequency related to a frequency of the received signal.

20. The apparatus of claim 19, wherein the frequency related to a frequency of the received signal is a harmonic frequency of a frequency of the first transmitted signal.

21. The apparatus of claim 19, wherein the frequency related to a frequency of the received signal is an intermodulation frequency of a frequency of the first transmit signals and a frequency of the second transmit signals.

22. A method comprising:

determining desensitization in a received signal caused by odd-order harmonic distortion occurring from at least one transmit signal;

generating a baseband replica harmonic distortion signal using the transmit signal;

converting the baseband replica harmonic distortion signal to a low frequency harmonic distortion signal, and

subtracting the low frequency harmonic distortion signal from a downconverted received signal to cancel the odd-order harmonic distortion from the downconverted received signal to create a corrected signal.

23. The method of claim 22 further comprising filtering the downconverted received signal using a low pass filter where the low pass filter has a function similar to a low pass filter of a receiver receiving the received signal.

24. The method of claim 22, wherein the odd-order harmonic distortion is determined based on the frequency of one of the transmit signals.

25. The method of claim 24, wherein a harmonic frequency of the odd-order harmonic distortion is determined by a function of a multiple of the at least one transmit signals.

26. The method of claim 22, further comprising sampling the transmit signal near a Nyquist limit of the transmit signal to avoid aliasing where the sampling is performed prior to generating the baseband replica harmonic distortion signal.

27. The method of claim 22, wherein generating the baseband replica harmonic distortion signal comprises generating the baseband replica harmonic distortion signal using interpolated complex signals.

28. The method of claim 22, wherein generating the baseband replica harmonic distortion signal comprises generating the baseband replica harmonic distortion signal using complex multiplication of a direct current baseband replica signal and an intermediate frequency signal having frequency that is the difference between a frequency of the local oscillator and a frequency of the odd order distortion.

29. The method of claim 22, wherein generating the baseband replica harmonic distortion signal comprises generating the baseband replica harmonic distortion signal using the frequency separation of the transmit signals.

30. The method of claim 22, wherein generating the baseband replica harmonic distortion signal includes determining a demodulation signal using a power function of the at least one transmit signal.

31. The method of claim 22 further comprising scaling the generated baseband replica harmonic distortion signal according to an expected distortion level using a function of a power level of the transmit signal and a gain of a receiver.

32. The method of claim 22, wherein a low frequency of the baseband replica harmonic distortion signal is centered on direct current.

33. The method of claim 22 further comprising converting the baseband replica harmonic distortion signal to a low frequency replica harmonic distortion signal using complex multiplication on the baseband harmonic distortion signal and a clock signal having a frequency of a down-converted odd order harmonic signal.