Systems, circuits and methods for adapting parameters of a linear equalizer in a receiver
View Patent ↗A receiver is optimized by adapting parameters of a linear equalizer component within the receiver. Data decisions and error decisions are generated. These data decision and error decisions are used to derive an error rate of data by measuring the number of margin hits that occur. A balance value is also calculated from the data decisions and the error decisions. The balance value is used to update parameters of the linear equalizer. The updating of the parameter continues until the number of margin hits has been minimized.
1. A method for offset cancellation of a linear equalizer in a receiver, comprising:
receiving a plurality of data decisions and a plurality of error decisions;
determining a number of margin hits based on the data decisions and the error decisions, wherein a margin hit indicates that one of the data decisions differs from one of the error decisions; and
sweeping an input of a digital to analog converter (DAC) coupled to the linear equalizer by varying the input of the DAC and injecting an output of the DAC into the linear equalizer until the number of margin hits is minimized.
2. The method of claim 1 , wherein the sweeping of the input comprises a steepest descent algorithm.
3. The method of claim 2 , wherein the steepest descent algorithm comprises a gradient function to determine a direction of the input of the DAC which decreases the number of margin hits most rapidly.
4. The method of claim 1 , wherein the DAC comprises a 6-bit current-mode digital to analog converter.
5. The method of claim 1 , wherein the sweeping of the input of the DAC is controlled by a microcontroller.
6. The method of claim 1 , wherein the sweeping of the input of the DAC is controlled by off-chip software.
7. The method of claim 1 , wherein the output of the DAC comprises a differential current.
8. The method of claim 1 , wherein the plurality of data decisions are generated from data slicers that decide if an output of a summer is a logical 1 or a logical 0.
9. The method of claim 8 , where in the plurality of error decisions are generated from error slicers that compare the output of the summer with a target signal eye opening level.
10. A system comprising:
a decision feedback equalizer configured to generate a plurality of data decisions and a plurality of error decisions;
a logic module configured to determine a number of margin hits based on the data decisions and the error decisions, wherein a margin hit indicates that one of the data decisions differs from one of the error decisions; and
a digital to analog converter (DAC) coupled to a linear equalizer,
wherein an input of the DAC is swept by varying the input of the DAC and injecting an output of the DAC into the linear equalizer until the number of margin hits-is minimized.
11. The system of claim 10 , wherein the sweeping of the input comprises a steepest descent algorithm.
12. The system of claim 11 , wherein the steepest descent algorithm comprises a gradient function to determine a direction of the input of the DAC which decreases the number of margin hits most rapidly.
13. The system of claim 10 , wherein the DAC comprises a 6-bit current-mode digital to analog converter.
14. The system of claim 10 , wherein the logic module comprises a microcontroller.
15. The system of claim 10 , wherein the logic module comprises off-chip software.
16. The system of claim 11 , wherein the output of the DAC comprises a differential current.
17. The system of claim 10 , wherein the plurality of data decisions are generated from data slicers that decide if an output of a summer is a logical 1 or a logical 0.
18. The system of claim 17 , wherein the plurality of error decisions are generated from error slicers that compare the output of the summer with a target signal eye opening level.
19. A method for optimization of a linear equalizer in a receiver, comprising:
receiving a plurality of data decisions and a plurality of error decisions;
determining a number of margin hits, wherein a margin hit indicates that one of the data decisions differs from one of the error decisions; and
sweeping a gain value of the linear equalizer until the number of margin hits is minimized.
20. The method of claim 19 , wherein the sweeping of the gain value is performed by a microcontroller.
21. The method of claim 19 , wherein the gain value is constrained by an output swing of a variable gain amplifier (VGA) coupled to the linear equalizer.
22. The method of claim 19 , wherein the sweeping of the gain value uses a steepest descent algorithm.
23. The method of claim 22 , wherein the steepest descent algorithm uses a gradient function to determine a direction of the sweeping of the gain value which decreases the number of margin hits most rapidly.
24. The method of claim 19 , wherein the sweeping of the gain value is performed by off-chip software.
25. The method of claim 19 , wherein the plurality of data decisions are generated from data slicers that decide if an output of a summer is a logical 1 or a logical 0.
26. The method of claim 25 , wherein the plurality of error decisions are generated from error slicers that compare the output of the summer with a target signal eye opening level.