Dynamic Cancellation of Passive Intermodulation Interference

• US 20120295558A1
• Filed: 09/09/2011
• Published: 11/22/2012
• Est. Priority Date: 05/20/2011
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Li, Shaohua, Baldemair, Robert, Cheng, Jung-fu, Ghasemzadeh, Farshid, Larsson, Magnus, Sköld, Johan, Wang, Meng
• Granted Patent: US 9,026,064 B2
• Time in Patent Office: Days
• US Class Current: 455/79
• 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

Abstract

A wireless communication node (10) dynamically estimates passive intermodulation (PIM) interference coupled into the node'"'"'s receive path from the transmission of a composite signal through the node'"'"'s transmit path. The node (10) then cancels the estimated PIM interference in the receive path. In some embodiments, the node dynamically estimates the PIM interference as a function of the composite signal that models PIM interference generation and coupling in the node (10) according to one or more coefficients (30). The coefficients (30) may be determined by transmitting a test signal (34) during a test stage, when the node (10) is not scheduled to receive any signal. Later, when the composite signal (18) is transmitted, the node (10) uses the coefficients (10) to dynamically estimate and cancel the resulting PIM interference.

Claims

1-22. -22. (canceled)

23. A wireless communication node comprising:

a transceiver with a transmit path and a receive path;

an estimation circuit configured to dynamically estimate passive intermodulation (PIM) interference coupled into the receive path from the transmission of a composite signal through the transmit path, wherein the composite signal includes component signals of different frequencies; and

a cancellation circuit configured to cancel the estimated PIM interference in the receive path.

24. The wireless communication node of claim 23, wherein the estimation circuit is configured to dynamically estimate the PIM interference as a function of the composite signal.

25. The wireless communication node of claim 24, wherein said function includes one or more coefficients that model generation of PIM interference in the transmit path and coupling of PIM interference from the transmit path into the receive path.

26. The wireless communication node of claim 25, further comprising an analysis circuit configured to determine the one or more coefficients by:

measuring interference coupled into the receive path from the transmission of a test signal through the transmit path during a time in which the transceiver is not scheduled to receive any signal; and

estimating the one or more coefficients as a function of the test signal and the measured interference.

27. The wireless communication node of claim 25, further comprising an analysis circuit configured to periodically update values of the one or more coefficients to reflect adjustments to the transmit path.

28. The wireless communication node of claim 25, further comprising an analysis circuit configured to periodically adjust the number of said coefficients.

29. The wireless communication node of claim 28, further comprising an error detection circuit configured to determine the extent to which previous cancellation of estimated PIM interference has decreased error rates.

30. The wireless communication node of claim 28, further comprising an error detection circuit configured to determine the extent to which cancelling estimated PIM interference has decreased error rates towards a target error rate, and wherein said adjustment is at least partly based on that determination.

31. The wireless communication node of claim 25, wherein said function is a polynomial with the composite signal as an independent variable and the one or more coefficients as coefficients of the polynomial.

32. The wireless communication node of claim 23, further comprising an interference monitoring circuit configured to monitor statistics regarding a received interference level at the transceiver and wherein the cancellation circuit is configured to selectively cancel PIM interference in the receive path depending on said statistics.

33. The wireless communication node of claim 32, wherein the cancellation circuit is configured to selectively cancel PIM interference by cancelling PIM interference if the statistics indicate the received interference level exceeds a predefined threshold level and has low variance, and refraining from cancelling PIM interference if the statistics indicate otherwise.

34. A method implemented by a wireless communication node that includes a transceiver, the method comprising:

dynamically estimating passive intermodulation (PIM) interference coupled into the receive path of the transceiver from the transmission of a composite signal through the transmit path of the transceiver, wherein the composite signal includes component signals of different frequencies; and

cancelling the estimated PIM interference in the receive path.

35. The method of claim 34, wherein said dynamically estimating comprises dynamically estimating the PIM interference as a function of the composite signal.

36. The method of claim 35, wherein said function includes one or more coefficients that model generation of PIM interference in the transmit path and coupling of PIM interference from the transmit path into the receive path.

37. The method of claim 36, further comprising determining the one or more coefficients by:

transmitting a test signal through the transmit path during a time in which the transceiver is not scheduled to receive any signal;

measuring interference coupled into the receive path from the transmission of the test signal; and

estimating the one or more coefficients as a function of the test signal and the measured interference.

38. The method of claim 36, further comprising periodically updating values of the one or more coefficients to reflect changes at the wireless communication node.

39. The method of claim 36, further comprising periodically adjusting the number of said coefficients.

40. The method of claim 39, wherein said adjustment is at least partly based on the extent to which previous cancellation of estimated PIM interference has decreased error rates.

41. The method of claim 39, wherein said adjustment is at least partly based on the extent to which cancelling estimated PIM interference has decreased error rates towards a target error rate.

42. The method of claim 36, wherein said function is a polynomial with the composite signal as an independent variable and the one or more coefficients as coefficients of the polynomial.

43. The method of claim 34, further comprising monitoring statistics regarding a received interference level at the transceiver and selectively cancelling PIM interference in the receive path depending on said statistics.

44. The method of claim 43, wherein said selectively cancelling comprises cancelling PIM interference if the statistics indicate the received interference level exceeds a predefined threshold level and has low variance, and refraining from cancelling PIM interference if the statistics indicate otherwise.