Sign-based general zero-forcing adaptive equalizer control

• US 8,213,494 B2
• Filed: 06/22/2009
• Issued: 07/03/2012
• Est. Priority Date: 06/20/2008
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Hidaka, Yasuo
• Primary Examiner(s): Puente, Eva
• Assistant Examiner(s): Guarino, Rahel
• Application Number:
  US12/489,356
• Publication Number:
  US 20090316771A1
• Time in Patent Office: 1,107 Days
• Field of Search: 375/349, 375/348, 375/233, 455/226.1, 455/134, 455/135, 455/136, 708/323
• US Class Current: 375/233
• CPC Class Codes: H04L 2025/0349 as a feedback filter
• CPC Class Codes: H04L 2025/03681 Control of adaptation
• CPC Class Codes: H04L 2025/03783 Details of reference signals
• CPC Class Codes: H04L 25/03057 with a recursive structure H04L25/03031 takes precedence
• CPC Class Codes: H04L 7/0025 interpolation of clock signal

Abstract

In one embodiment, a system includes one or more digital feedback equalizers (DFEs) that include one or more residual intersymbol interference (ISI) detectors, one or more column balancers, and one or more weight selectors. The residual ISI detectors produce a first output signal indicating whether the residual ISI of a received input signal has a positive sign or a negative sign. The column balancers select one of the first output signals to produce a second output signal. The weight selectors access one of the weight values. The weight value corresponds to the column balancer that produced the second output signal and the residual ISI detector that produced the first output signal, and has a magnitude that is substantially independent of the sign of the residual ISI. The weight selectors produce a third output signal based on the weight value and the sign of the residual ISI.

Claims

1. A system comprising:

one or more residual intersymbol interference (ISI) detectors that are each configured to receive from a decision feedback equalizer (DFE) a data signal or an error signal comprising residual ISI and produce a first output signal indicating whether the residual ISI has a positive sign or a negative sign;

one or more column balancers that are each configured to receive, from one or more of the ISI residual detectors, respective first output signals and select one of the received first output signals to produce a second output signal; and

one or more weight selectors that are each configured to;

receive, from a particular one of the one or more column balancers, a respective second output signal;

access from among a plurality of weight values one of the weight values for the received second output signal, the accessed one of the weight values;

corresponding to the particular one column balancer; and

the residual ISI detector that produced the selected first output signal to produce the received second output signal; and

having a magnitude that is substantially independent of the sign of the residual ISI indicated by the selected first output signal to produce the received second output signal; and

produce a third output signal based on the accessed one of the weight values and the sign of the residual ISI indicated by the selected first output signal to produce the received second output signal, the third signal being usable in producing one or more fourth output signals representing one or more control variables for one or more equalizers.

2. The system of claim 1, wherein the plurality of weight values reside in a two-dimensional weight register file, the plurality of weight values being indexed by column balancer and residual ISI detector.

3. The system of claim 1, wherein an integrator is used for each of the third output signals to produce the corresponding fourth output signal by integrating the third output signal.

4. The system of claim 1, wherein a probability of the column balancer selecting any one of the received first output signals is equal to a probability of the column balancer selecting any other one of the received first output signals to produce the second output signal.

5. The system of claim 4, wherein the column balancer is configured to select from among the received first output signals randomly.

6. The system of claim 4, wherein the column balancer is configured to select from among the received first output signals sequentially.

7. The system of claim 4, wherein the column balancer is configured to select a same one of the received first output signals twice in a row.

8. The system of claim 1, wherein the accessed one of the weight values is calculated from a derivative of an average of residual ISI in a worst-case transmission channel with respect to one or more of the control variables for one or more of the equalizers.

9. The system of claim 1, wherein:

there are two weight selectors;

the third output signal of a first one of the weight selectors is for use in producing a linear equalizer (LE) parameter signal; and

the third output signal of a second one of the weight selectors is for use in producing a boundary feedback (FB) coefficient signal and a data FB coefficient signal for the DFE.

10. The system of claim 1, wherein the data FB coefficient is derived from the boundary FB coefficient using a scaling factor.

11. The system of claim 1, wherein different ones of the residual ISI detectors use different bit patterns or different schemes to detect the residual ISI.

12. The system of claim 1, where the residual ISI detectors are programmable.

13. The system of claim 1, wherein functions of a plurality of the residual ISI detectors are implemented using one multiplexed residual ISI detector to produce the first output signals.

14. The system of claim 1, wherein functions of a plurality of the column balancers are implemented using one multiplexed column balancer to produce the second output signals.

15. The system of claim 1, wherein functions of a plurality of the weight selectors are implemented using one multiplexed weight selector to produce the third output signals.

16. The system of claim 1, wherein functions of the column balancer and a corresponding one of the weight selectors are implemented together.

17. The system of claim 1, wherein functions of a plurality of the residual ISI detectors and a plurality of the column balancers are implemented together.

18. A method comprising:

by each of one or more residual intersymbol interference (ISI) detectors;

receiving from a decision feedback equalizer (DFE) a data signal or an error signal comprising residual ISI; and

producing a first output signal indicating whether the residual ISI has a positive sign or a negative sign;

by each of one or more column balancers;

receiving, from one or more of the ISI residual detectors, respective first output signals; and

selecting one of the received first output signals to produce a second output signal;

by each of one or more weight selectors;

receiving, from a particular one of the one or more column balancers, a respective second output signal;

accessing from among a plurality of weight values one of the weight values for the received second output signal, the accessed one of the weight values;

corresponding to the particular one column balancer and the residual ISI detector that produced the selected first output signal to produce the received second output signal; and

having a magnitude that is substantially independent of the sign of the residual ISI indicated by the selected first output signal to produce the received second output signal; and

producing a third output signal based on the accessed one of the weight values and the sign of the residual ISI indicated by the selected first output signal to produce the received second output signal, the third signal being usable in producing one or more fourth output signals representing one or more control variables for one or more equalizers.

19. A system comprising:

means for producing one or more first output signals, each first output signal indicating whether a corresponding residual intersymbol interference (ISI) has a positive sign or a negative sign;

means for selecting one of the one or more first output signals to produce a second output signal;

means for accessing from among a plurality of weight values one of the weight values for the second output signal, the accessed one of the weight values;

corresponding to means for selecting one of the one or more first output signals to produce the second output signal; and

having a magnitude that is substantially independent of the sign of the residual ISI indicated by the selected first output signal to produce the second output signal; and

means for producing a third output signal based on the accessed one of the weight values and the sign of the residual ISI indicated by the selected first output signal to produce the second output signal, the third signal being usable in producing one or more fourth output signals representing one or more control variables for one or more equalizers.