Method and apparatus for eye-opening based optimization

• US 7,400,694 B1
• Filed: 11/01/2004
• Issued: 07/15/2008
• Est. Priority Date: 11/01/2004
• Status: Active Grant

• Current Assignee: Synopsys Incorporated
• Original Assignee: Synopsys Incorporated
• Inventors: Weinlader, Daniel Keith, Sonntag, Jeffrey Lee, Stonick, John Theodore
• Primary Examiner(s): Ghayour; Mohammad H.
• Assistant Examiner(s): Malek; Leila
• Application Number:
  US10/978,764
• Time in Patent Office: 1,352 Days
• Field of Search: 375/316, 375/350, 375/349, 369/47.26, 369/53.35, 369/59.17, 708/300, 708/322, 708/323
• US Class Current: 375/350
• CPC Class Codes: H04L 25/063 Setting decision thresholds using feedback techniques only

Abstract

An eye opening measurement technique, that does not interrupt a receiver'"'"'s normal operation, is used as a metric for optimizing any selected parameters of the receiver'"'"'s operation. If eye opening size decreases, as a result of a change to a receiver parameter, the polarity for stepwise changes is reversed such that the next change is in the opposite direction. Other types of search procedures can be used.

Eye opening size is the difference between the eye'"'"'s upper and lower edges. Measurement of eye opening size is accomplished using a data and auxiliary slicer that find each “edge” of an eye opening based upon the slicers'"'"' level of agreement.

Depending upon the level of agreement, and whether symbols of the upper or lower region of the eye are counted, the threshold of the auxiliary slicer can be adjusted in the direction necessary to converge on the eye edge sought.

Claims

1. A method for adapting a receiver of a data transmission system which uses only two slicers to determine an eye opening, comprising:

receiving a signal at a low-pass filter (LPF), wherein the signal is associated with a data transmission stream, and wherein the LPF'"'"'s bandwidth is adjustable;

supplying the LPF'"'"'s output signal to a single data slicer and single auxiliary slicer, wherein the data slicer is used to compare the LPF'"'"'s output signal to a fixed threshold for identifying symbols in the data transmission stream, and wherein the auxiliary slicer is used to compare the LPF'"'"'s output signal to an adjustable threshold for identifying an eye opening size for the LPF'"'"'s output signal;

determining a first eye opening size by;

adjusting the auxiliary slicer'"'"'s threshold towards an upper edge of a first eye opening as a result of comparisons between the auxiliary slicer and the data slicer; and

adjusting the auxiliary slicer'"'"'s threshold towards a lower edge of the first eye opening as a result of comparisons between the auxiliary slicer and the data slicer;

performing a first adjustment, in a first direction, to the LPF'"'"'s bandwidth, wherein performing the first adjustment causes the LPF'"'"'s output signal to have an eye opening size that is different from the first eye opening size;

determining a second eye opening size, as a result of the first adjustment, by;

adjusting the auxiliary slicer'"'"'s threshold towards an upper edge of a second eye opening as a result of comparisons between the auxiliary slicer and the data slicer; and

adjusting the auxiliary slicer'"'"'s threshold towards a lower edge of the second eye opening as a result of comparisons between the auxiliary slicer and the data slicer;

comparing the first eye opening size to the second eye opening size; and

performing a second adjustment, to the LPF'"'"'s bandwidth, in a direction dependent upon a result of the comparison.

2. The method of claim 1, further comprising:

continuing normal reception of data transmissions, from the data slicer, during determinations of an eye opening size.

3. The method of claim 1, wherein the step of performing a second adjustment further comprises:

adjusting the LPF'"'"'s bandwidth in the first direction if the second eye opening size is greater than the first eye opening size and adjusting the LPF'"'"'s bandwidth in a second direction if the second eye opening size is less than the first eye opening size.

4. The method of claim 1, wherein each step of adjusting the auxiliary slicer'"'"'s threshold towards an edge of an eye further comprises:

counting each disagreement between the data slicer and the auxiliary slicer when the data slicer indicates reception of a symbol of the eye edge sought;

comparing the disagreement count to a first threshold; and

adjusting the auxiliary slicer'"'"'s threshold as a result of the comparison of the disagreement count to a first threshold.

5. The method of claim 4, wherein the step of adjusting further comprises:

adjusting the auxiliary slicer'"'"'s threshold further from a center of an eye opening if the disagreement count is less than the first threshold; and

adjusting the auxiliary slicer'"'"'s threshold towards a center of an eye opening if the disagreement count is greater than the first threshold.

6. The method of claim 1, wherein the auxiliary slicer is integrated on an integrated circuit and the data slicer is integrated on the same, physically contiguous, integrated circuit.

7. A system for adapting a receiver of a data transmission system which uses only two slicers to determine an eye opening, comprising:

a low-pass filter (LPF) configured to receive a signal, wherein the signal is associated with a data transmission stream, and wherein the LPF'"'"'s bandwidth is adjustable;

a sub-system configured to supply the LPF'"'"'s output signal to a single data slicer and a single auxiliary slicer, wherein the data slicer is used to compare the LPF'"'"'s output signal to a fixed threshold for identifying symbols in the data transmission stream, and wherein the auxiliary slicer is used to compare the LPF'"'"'s output signal to an adjustable threshold for identifying an eye opening size for the LPF'"'"'s output signal;

a sub-system configured to determine a first eye opening size by;

adjusting the auxiliary slicer'"'"'s threshold towards an upper edge of a first eye opening as a result of comparisons between the auxiliary slicer and the data slicer; and

adjusting the auxiliary slicer'"'"'s threshold towards a lower edge of the first eye opening as a result of comparisons between the auxiliary slicer and the data slicer;

a sub-system configured to perform a first adjustment, in a first direction, to the LPF'"'"'s bandwidth, wherein performing the first adjustment causes the LPF'"'"'s output signal to have an eye opening size that is different from the first eye opening size;

a sub-system configured to determine a second eye opening size, as a result of the first adjustment, by;

adjusting the auxiliary slicer'"'"'s threshold towards an upper edge of a second eye opening as a result of comparisons between the auxiliary slicer and the data slicer; and

adjusting the auxiliary slicer'"'"'s threshold towards a lower edge of the second eye opening as a result of comparisons between the auxiliary slicer and the data slicer;

a sub-system configured to compare the first eye opening size to the second eye opening size; and

a sub-system configured to perform a second adjustment, to the LPF'"'"'s bandwidth, in a direction dependent upon a result of the comparison.