Equalizer characteristics optimizing method and transmission system

• US 20100008413A1
• Filed: 09/18/2009
• Published: 01/14/2010
• Est. Priority Date: 03/27/2007
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Yamazaki, Manabu, Tosaka, Masaki
• Granted Patent: US 8,194,727 B2
• Time in Patent Office: Days
• US Class Current: 375/232
• CPC Class Codes: H04B 3/06 by the transmitted signal
• CPC Class Codes: H04L 2025/03356 Baseband transmission
• CPC Class Codes: H04L 25/063 Setting decision thresholds using feedback techniques only
• CPC Class Codes: H04L 7/02 Speed or phase control by the received code signals, the signals containing no special synchronisation information H04L7/0075 takes precedence

Abstract

An equalizer characteristics optimizing method includes acquiring a recovery clock timing from a reception signal; acquiring a predetermined sampling clock timing with respect to the recovery clock timing; latching the reception signal at the recovery clock timing; latching the reception signal at the sampling clock timing; comparing logic values obtained in the latching steps; collecting, after changing a characteristics setting of an equalizer, logic value comparison result data by repeating the recovery clock acquiring step, the acquiring of the sampling clock timing, the latching of the reception signal at the individual clock timings, and the comparing of the logic values, using the changed characteristics setting; and determining an optimum characteristics setting of an equalizer based on the collected logic value comparison result data.

Claims

1. An equalizer characteristics optimizing method comprising:

acquiring a recovery clock timing from a reception signal whose frequency characteristics are compensated by an equalizer;

acquiring a predetermined sampling clock timing with respect to the recovery clock timing;

latching, at the recovery clock timing, the reception signal whose frequency characteristics are compensated by the equalizer;

latching, at the sampling clock timing, the reception signal whose frequency characteristics are compensated by the equalizer;

comparing a logic value obtained by the latching, at the recovery clock timing, with a logic value obtained by the latching, at the sampling clock timing;

collecting logic value comparison result data by repeating, after a characteristics setting of the equalizer is changed, the acquiring a recovery clock timing, the acquiring a predetermined sampling clock timing, the latching, at the recovery clock timing, the latching, at the sampling clock timing, and the comparing with regard to the reception signal whose frequency characteristics are compensated by the equalizer with the changed characteristics setting; and

determining an optimum characteristics setting of the equalizer based on the logic value comparison result data collected by the collecting logic value comparison result data.

2. The equalizer characteristics optimizing method according to claim 1, wherein the collecting includes changing the equalizer characteristics setting by independently varying a predetermined first coefficient for controlling a low-frequency band of the frequency characteristics of the equalizer and a predetermined second coefficient for controlling a high-frequency band of the frequency characteristics of the equalizer,

and wherein the determining an optimum characteristics setting includes obtaining a two-dimensional table of comparison results obtained by the comparing and collected by the collecting with respect to the predetermined first coefficient and the predetermined second coefficient, and determining a center of gravity of the comparison results in the two-dimensional table that indicate correspondence of the compared logic values.

3. The equalizer characteristics optimizing method according to claim 1, wherein the determining an optimum characteristics setting includes obtaining an average value of comparison results obtained by the comparing and collected by the collecting, by using a filter configured to average the comparison results, and determining the optimum characteristics setting of the equalizer based on the average value obtained each time the equalizer characteristics setting is changed.

4. The equalizer characteristics optimizing method according to claim 1, wherein the acquiring a predetermined sampling clock timing includes acquiring 2n sampling clock timings of which half are shifted in a leading direction and the other half are shifted in a lagging direction symmetrically with respect to the recovery clock timing, where n is an integer of 1 or more.

5. The equalizer characteristics optimizing method according to claim 1, wherein the acquiring a predetermined sampling, clock timing includes acquiring the sampling clock timing in either a leading or a lagging direction alone with respect to the recovery clock timing.

6. The equalizer characteristics optimizing method according to claim 1, wherein the acquiring a predetermined sampling clock timing includes sweeping the sampling clock timing within a predetermined phase range with respect to the recovery clock timing,

wherein the comparing includes determining a weight that indicates a ratio of correspondence in the logic value comparison results based on the logic value comparison result that is obtained by the sweeping each time the equalizer characteristics setting is changed,

and wherein the determining of an optimum characteristics setting includes determining the optimum characteristics setting of the equalizer based on data of the weight.

7. An equalizer characteristics optimizing method comprising:

comparing logic values obtained by latching, at a recovery clock timing and a sampling clock timing, a reception signal whose frequency characteristics are compensated by an equalizer;

generating the recovery clock timing based on a comparison result obtained by the comparing;

generating the sampling clock timing with respect to the recovery clock timing;

collecting logic value comparison result data by repeating, after a characteristics setting of the equalizer is changed, the generating the recovery clock timing, the generating the sampling clock timing, the latching, and the comparing with regard to the reception signal whose frequency characteristics are compensated by the equalizer with the changed characteristics setting; and

determining an optimum characteristics setting of the equalizer based on the logic value comparison result data collected by the collecting logic value comparison result data.

8. A transmission system comprising:

a transmission interface having a function of optimizing characteristics of an equalizer;

a logic value comparing unit configured to compare logic values obtained by latching, at a recovery clock timing and a sampling clock timing, a reception signal whose frequency characteristics are compensated by the equalizer;

a recovery clock generating unit configured to generate the recovery clock timing based on a comparison result obtained by the logic value comparing unit;

a sampling clock generating unit configured to generate the sampling clock timing with respect to the recovery clock timing;

a frequency characteristics control unit configured to collect logic value comparison result data by repeating, after a characteristics setting of the equalizer is changed, generation of the recovery clock timing by the recovery clock generating unit, generation of the sampling clock timing by the sampling clock generating unit, the latching, and comparison of logic values by the logic value comparing unit, with regard to the reception signal whose frequency characteristics are compensated by the equalizer with the changed characteristics setting; and

an optimum setting determining unit configured to determine an optimum characteristics setting of the equalizer based on the logic value comparison result data collected by the frequency characteristics control unit.

9. The transmission system according to claim 8, wherein the frequency characteristics control unit is configured to change the equalizer characteristics setting by independently varying a predetermined first coefficient for controlling a low-frequency band of the frequency characteristics of the equalizer and a predetermined second coefficient for controlling a high-frequency band of the frequency characteristics of the equalizer;

and wherein the optimum setting determining unit is configured to determine the optimum characteristics setting of the equalizer by obtaining a two-dimensional table of comparison results obtained by the logic value comparing unit and collected by the frequency characteristics control unit with respect to the predetermined first coefficient and the predetermined second coefficient, and configured to determine a center of gravity of the comparison results in the two-dimensional table that indicate correspondence of the compared logic values.

10. The transmission system according to claim 8, wherein the optimum setting determining unit is configured to obtain an average value of comparison results obtained by the logic value comparing unit and collected by the frequency characteristics control unit using a filter that averages the comparison results, and configured to determine the optimum characteristics setting of the equalizer based on the average value obtained each time the equalizer characteristics setting is changed.

11. The transmission system according to claim 8, wherein the sampling clock generating unit is configured to generate 2n sampling clock timings of which half are shifted in a leading direction and half are shifted in a lagging direction symmetrically with respect to the recovery clock timing, where n is an integer of 1 or more.

12. The transmission system according to claim 8, wherein the sampling clock generating unit is configured to acquire the sampling clock timing in either a leading or a lagging direction alone with respect to the recovery clock timing.

13. The transmission system according to claim 8, wherein the sampling clock generating unit is configured to sweep the sampling clock timing within a predetermined phase range with respect to the recovery clock timing,

wherein the logic value comparing unit is configured to determine a weight that indicates a ratio of correspondence in logic value comparison results based on the logic value comparison result that is obtained by sweeping of the sampling clock timing each time the equalizer characteristics setting is changed,

and wherein the optimum setting determining unit is configured to determine the optimum characteristics setting of the equalizer based on data of the weight.