Method and system for crosstalk cancellation

• US 8,068,406 B2
• Filed: 10/19/2009
• Issued: 11/29/2011
• Est. Priority Date: 08/07/2003
• Status: Expired due to Fees

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Quellan, Inc. (Renesas Electronics Corporation)
• Inventors: Vrazel, Michael G., Summers, Charles, Kim, Andrew Joo, Bajekal, Sanjay
• Primary Examiner(s): MARCELO, MELVIN C
• Application Number:
  US12/581,511
• Publication Number:
  US 20100039923A1
• Time in Patent Office: 771 Days
• Field of Search: 370/201, 370/286
• US Class Current: 370/201
• CPC Class Codes: H04B 3/23 using a replica of transmitted signal in the time domain, e.g. echo cancellers
• CPC Class Codes: H04B 3/238 using initial training sequence
• CPC Class Codes: H04B 3/32 Reducing cross-talk, e.g. by compensating
• CPC Class Codes: H04J 1/12 Arrangements for reducing cross-talk between channels in line transmission systems H04B3/32; in cables or lines H04B3/26 - H04B3/30

Abstract

Signals propagating in one communication channel can generate crosstalk interference in another communication channel. A crosstalk cancellation device can process the signals causing the crosstalk interference and generate a crosstalk cancellation signal that can compensate for the crosstalk when applied to the channel receiving crosstalk interference. The crosstalk cancellation device can include a model of the crosstalk effect that generates a signal emulating the actual crosstalk both in form an in timing. The crosstalk cancellation device can include a controller that monitors crosstalk-compensated communication signals and adjusts the model to enhance crosstalk cancellation performance. The crosstalk cancellation device can have a mode of self configuration or calibration in which defined test signals can be transmitted on the crosstalk-generating channel and the crosstalk-receiving channel.

Claims

1. A method for canceling crosstalk an aggressor signal applies to a victim signal, comprising:

obtaining a sample of the aggressor signal;

processing the sample with a circuit that comprises a crosstalk model to produce a crosstalk cancellation signal that is temporally aligned to the crosstalk; and

applying the temporally aligned crosstalk cancellation signal to the victim signal.

2. The method of claim 1, wherein the circuit comprises an adjustable delay that temporally aligns the crosstalk cancellation signal to the crosstalk.

3. The method of claim 1, wherein the aggressor signal conveys first data and the victim conveys second data, and

wherein the method comprises establishing a predetermined phase relationship between crosstalk cancellation signal and the crosstalk.

4. The method of claim 1, wherein the aggressor signal propagates on a first circuit trace and wherein the victim signal propagates on a second circuit trace disposed adjacent the first circuit trace.

5. The method of claim 1, wherein an integrated circuit comprises the crosstalk model, and

wherein upon applying the temporally aligned crosstalk cancellation signal to the victim signal, the crosstalk cancellation signal is about 180 degrees out of phase with the crosstalk.

6. The method of claim 1, wherein the crosstalk model comprises a crosstalk modeling filter, and

wherein the method further comprises reducing residual crosstalk in response to adjusting the crosstalk modeling filter.

7. The method of claim 1, wherein obtaining the sample of the aggressor signal comprises obtaining the sample from an aggressor communication channel,

wherein applying the temporally aligned crosstalk cancellation signal to the victim signal comprises applying the temporally aligned crosstalk cancellation signal to a victim communication channel, and

wherein the method further comprises:

transmitting a test signal on the aggressor communication channel to produce test crosstalk on the victim communication channel; and

adjusting the crosstalk model in response to analyzing the test crosstalk.

8. The method of claim 1, further comprising:

transmitting a first test signal on a first signal path that conveys the aggressor signal;

transmitting a second test signal on a second signal path that conveys the victim signal; and

refining a signal processing parameter of the circuit.

9. A method for reducing interference on a first signal that communicates information, comprising the steps of:

tapping off a portion of a second signal imposing the interference on the first signal;

feeding the tapped off portion of the second signal to a circuit that emulates the imposed interference;

shifting the emulated interference in time to provide a time match between the emulated interference and the imposed interference; and

reducing the imposed interference in response to applying the shifted emulated interference to the first signal.

10. The method of claim 9, wherein the circuit comprises a crosstalk modeling filter, and

wherein the method further comprises the steps of:

adjusting the crosstalk modeling filter with a control circuit to reduce residual interference on the first signal.

11. The method of claim 9, wherein the circuit is an integrated circuit,

wherein a first circuit trace carries the first signal and runs alongside a second circuit trace that carries the second signal,

wherein the first signal conveys first data,

wherein the second signal conveys second data, and

wherein the method further comprises transmitting a test signal on the second circuit trace to produce test interference on the first circuit trace.

12. The method of claim 9, wherein the time match comprises a predetermined phase relationship between the emulated interference and the imposed interference.

13. The method of claim 9, wherein applying the shifted emulated interference to the first signal comprises producing a third signal, and

wherein the method further comprises refining the time match between the emulated interference and the imposed interference based on an analysis of the third signal.

14. The method of claim 9, wherein the circuit comprises a model, and

wherein the method further comprises the steps of:

coupling test interference onto a first communication channel that is operative to carry the first signal in response to transmitting a test signal on a second communication channel that is operative to carry the second signal; and

setting a parameter of the model in response to analyzing the test interference.

15. A method for improving a first communication signal comprising interference due to a transfer of energy from a second communication signal, comprising the steps of:

providing a first signal in response to sampling the second communication signal;

generating a second signal in response to processing the first signal with an integrated circuit that models the transfer of energy;

synchronizing the second signal to the interference; and

applying the synchronized second signal to the first communication signal to cancel a substantial portion of the interference.

16. The method of claim 15, wherein the applying step comprises increasing openness of an eye in an eye diagram.

17. The method of claim 15, further comprising setting a plurality of modeling parameters for the integrated circuit in response to:

transmitting a first test signal on an aggressor channel that is operative to carry the second communication signal; and

transmitting a second test signal on a victim channel that is operative to carry the first communication signal, wherein the first test signal produces test interference propagating on the second communication channel with the second test signal.

18. The method of claim 15, wherein the generating step comprises operating a digital circuit at least one order of magnitude below a channel baud rate.

19. The method of claim 15, further comprising the steps of:

generating test crosstalk in response to transmitting a test signal on a channel; and

adjusting a modeling parameter based on an analysis of the generated crosstalk, wherein

processing the first signal comprises processing the first signal according to the adjusted modeling parameter.

20. The method of claim 15, further comprising the steps of:

conveying first data in response to transmitting the first communication signal on a first circuit trace; and

conveying second data in response to transmitting the second communication signal on a second circuit trace that extends alongside the first circuit trace.