METHOD AND APPARATUS FOR PERFORMANCE METRIC COMPATIBLE CONTROL OF DATA TRANSMISSION SIGNALS

• US 20080144742A1
• Filed: 02/28/2008
• Published: 06/19/2008
• Est. Priority Date: 11/01/2004
• Status: Active Grant

• Current Assignee: Synopsys Incorporated
• Original Assignee: Synopsys Incorporated
• Inventors: Weinlader, Daniel Keith, Sonntag, Jeffrey Lee, Yokoyama-Martin, David Andrew
• Granted Patent: US 8,015,539 B2
• Time in Patent Office: Days
• US Class Current: 375/319
• CPC Class Codes: H04L 1/20 using signal quality detector
• CPC Class Codes: H04L 25/0272 Arrangements for coupling to multiple lines, e.g. for differential transmission
• CPC Class Codes: H04L 25/0284 Arrangements to ensure DC-balance
• CPC Class Codes: H04L 25/0296 Arrangements to ensure DC-balance
• CPC Class Codes: H04L 25/4917 using multilevel codes

Abstract

The DC offset of a differential signal can be changed by differentially shifting the DC offset of each of its signals. Techniques are presented for changing, in a controlled way, the DC offset of a differential signal as received by a receiver of a data transmission system. Several classes of example embodiments, utilizing digitally controllable voltage or current sources, are presented. The classes differ based upon such factors as coupling capacitor arrangement and use of termination resistors. Specific embodiments, within each class, differ based upon such factors as whether voltage or current sources are used and the characteristics of such sources. Once the DC offset of a differential signal has been changed, the effect of such change on a performance metric can be measured. Example applications include the ability to determine a differential signal level that results in BER having a particular level and determination of differential signal margin.

Claims

1. A method for determining a non-normal differential-signal-level that is associated with a non-normal symbol-error-rate for a data transmission system, the method comprising:

receiving the non-normal symbol-error-rate for the data transmission system, wherein the non-normal symbol-error-rate is greater than the data transmission system'"'"'s symbol-error-rate under normal operating conditions;

receiving an input differential signal at an input of an adjustable DC-offset-circuit, wherein an output of the adjustable DC-offset-circuit is coupled with an input of a receiver;

determining the non-normal differential-signal-level by adjusting the output of the adjustable DC-offset-circuit so that a symbol-error-rate measured by the receiver is substantially equal to the non-normal symbol-error-rate; and

recording the non-normal differential-signal-level.

2. The method of claim 1, wherein the output of the adjustable DC-offset-circuit is adjusted using a digitally controllable voltage source.

3. The method of claim 1, wherein the output of the adjustable DC-offset-circuit is adjusted using a digitally controllable current source.

4. The method of claim 1, wherein the non-normal differential-signal-level is used to estimate the data transmission system'"'"'s symbol-error-rate under normal operating conditions.

5. The method of claim 1, wherein the input differential signal is received through coupling capacitors which are coupled with a transmitter.

6. An apparatus for determining a non-normal differential-signal-level that is associated with a non-normal symbol-error-rate for a data transmission system, the apparatus comprising:

a first receiving mechanism configured to receive the non-normal symbol-error-rate for the data transmission system, wherein the non-normal symbol-error-rate is greater than the data transmission system'"'"'s symbol-error-rate under normal operating conditions;

a second receiving mechanism configured to receive an input differential signal at an input of an adjustable DC-offset-circuit, wherein an output of the adjustable DC-offset-circuit is coupled with an input of a receiver;

a determining mechanism configured to determine the non-normal differential-signal-level by adjusting the output of the adjustable DC-offset-circuit so that a symbol-error-rate measured by the receiver is substantially equal to the non-normal symbol-error-rate; and

a recording mechanism configured to record the non-normal differential-signal-level.

7. The apparatus of claim 6, wherein the output of the adjustable DC-offset-circuit is adjusted using a digitally controllable voltage source.

8. The apparatus of claim 6, wherein the output of the adjustable DC-offset-circuit is adjusted using a digitally controllable current source.

9. The apparatus of claim 6, wherein the non-normal differential-signal-level is used to estimate the data transmission system'"'"'s symbol-error-rate under normal operating conditions.

10. The apparatus of claim 6, wherein the input differential signal is received through coupling capacitors which are coupled with a transmitter.

11. A computer-based system for determining a non-normal differential-signal-level that is associated with a non-normal symbol-error-rate for a data transmission system, the computer-based system comprising:

an adjustable DC-offset-circuit, wherein an input of the adjustable DC-offset-circuit receives an input differential signal, and wherein an output of the adjustable DC-offset-circuit is coupled with an input of a receiver;

a processor; and

a computer-readable storage medium storing instructions that when executed by the processor cause the computer-based system to;

receive the non-normal symbol-error-rate for the data transmission system, wherein the non-normal symbol-error-rate is greater than the data transmission system'"'"'s symbol-error-rate under normal operating conditions;

determine the non-normal differential-signal-level by adjusting the output of the adjustable DC-offset-circuit so that a symbol-error-rate measured by the receiver is substantially equal to the non-normal symbol-error-rate; and

record the non-normal differential-signal-level.

12. The computer-based system of claim 11, wherein the output of the adjustable DC-offset-circuit is adjusted using a digitally controllable voltage source.

13. The computer-based system of claim 11, wherein the output of the adjustable DC-offset-circuit is adjusted using a digitally controllable current source.

14. The computer-based system of claim 11, wherein the non-normal differential-signal-level is used to estimate the data transmission system'"'"'s symbol-error-rate under normal operating conditions.

15. The computer-based system of claim 11, wherein the input differential signal is received through coupling capacitors which are coupled with a transmitter.