Methods and systems for adaptive receiver equalization

• US 8,472,512 B2
• Filed: 05/09/2012
• Issued: 06/25/2013
• Est. Priority Date: 04/28/2000
• Status: Expired due to Fees

• Current Assignee: Avago Technologies International Sales Pte Limited (Broadcom, Inc.)
• Original Assignee: Broadcom Corporation (Broadcom, Inc.)
• Inventors: Buchwald, Aaron, Jiang, Xicheng, Wang, Hui, Baumer, Howard A., Madisetti, Avanindra
• Primary Examiner(s): Puente, Eva
• Application Number:
  US13/467,531
• Publication Number:
  US 20120243598A1
• Time in Patent Office: 412 Days
• Field of Search: 375/232
• US Class Current: 375/232
• CPC Class Codes: H03L 7/07 using several loops, e.g. for redundant clock signal generation
• CPC Class Codes: H03L 7/0814 the phase shifting device being digitally controlled
• CPC Class Codes: H03L 7/0816 the controlled phase shifter and the frequency- or phase-detection arrangement being connected to a common input
• CPC Class Codes: H03L 7/091 the phase or frequency detector using a sampling device H03L7/087 takes precedence
• CPC Class Codes: H04L 2025/03477 not time-recursive
• CPC Class Codes: H04L 2025/03617 Time recursive algorithms H04L2025/03643 takes precedence
• CPC Class Codes: H04L 25/03006 Arrangements for removing intersymbol interference
• CPC Class Codes: H04L 25/03885 adaptive
• CPC Class Codes: H04L 7/0025 interpolation of clock signal
• CPC Class Codes: H04L 7/0274 with Costas loop
• CPC Class Codes: H04L 7/0337 Selecting between two or more discretely delayed clocks or selecting between two or more discretely delayed received code signals

Abstract

Methods and systems for adaptively equalizing an analog information signal for a signal path, including sampling the analog information signal, thereby generating analog samples, and performing an equalizing process on the analog samples, wherein the equalizing includes processing an average of post-transition sample amplitudes and an average of steady state sample amplitudes of the analog samples to produce equalized analog samples.

Claims

1. A method for adaptively equalizing an analog information signal for a signal path, comprising:

sampling the analog information signal, thereby generating analog samples; and

performing an equalizing process on the analog samples, wherein the performing the equalizing process includes adjusting a difference between an average of post-transition sample amplitudes and an average of steady state sample amplitudes of the analog samples to produce equalized analog samples.

2. The method according to claim 1, further comprising:

quantizing the equalized analog samples of the analog information signal.

3. The method according to claim 2, wherein the performing the equalizing process comprises:

comparing a multi-level representation of the equalized samples with the quantized equalized samples;

performing a least-means-squared operation on results of the comparison;

adjusting an equalization coefficient with a result of the least-means-squared operation; and

repeating the comparing through the adjusting.

4. The method according to claim 1, wherein the performing includes performing the equalizing process at a sub-sample rate relative to the sampling of the analog information signal.

5. The method according to claim 1, wherein the performing includes performing the equalizing process at an off-set of a sub-sample rate relative to the sampling of the analog information signal.

6. The method according to claim 1, wherein the adjusting the difference comprises:

distinguishing between post-transition samples and steady-state samples;

integrating post-transition sample amplitudes;

integrating steady-state sample amplitudes;

determining a difference between the integrated post-transition sample amplitudes and the integrated steady-state sample amplitudes;

adjusting an equalization coefficient to minimize the difference between an average of the integrated post-transition sample amplitudes and an average of the integrated steady-state sample amplitudes; and

repeating the distinguishing through the adjusting.

7. The method according to claim 6, wherein the adjusting includes adjusting the difference at a sub-sample rate relative to the sampling of the analog information signal.

8. The method according to claim 6, wherein the adjusting includes adjusting the difference at an off-set of a sub-sample rate relative to the sampling the analog information signal.

9. The method according to claim 1, wherein the adjusting the difference comprises:

distinguishing between post-transition samples and steady-state samples;

averaging post-transition sample amplitudes;

averaging steady-state sample amplitudes;

determining a difference between the averaged post-transition sample amplitudes and the averaged steady-state sample amplitudes;

adjusting an equalization coefficient to minimize the difference between the averaged post-transition sample amplitudes and the averaged steady-state sample amplitudes; and

repeating the distinguishing through the adjusting.

10. The method according to claim 1, wherein the adjusting the difference comprises:

distinguishing between post-transition samples and steady-state samples;

accumulating post-transition sample amplitudes;

accumulating steady-state sample amplitudes;

determining a difference between the accumulated post-transition sample amplitudes and the accumulated steady-state sample amplitudes;

adjusting an equalization coefficient to minimize the difference between an average of the accumulated post-transition sample amplitudes and an average of the accumulated steady-state sample amplitudes; and

repeating the distinguishing through the adjusting.

11. The method according to claim 1, wherein the performing the equalizing process comprises minimizing inter-symbol interferences in the samples.

18. The method of claim 1, wherein the post-transition sample amplitudes represent amplitudes of the equalized analog samples after transitioning from a first amplitude to a second amplitude before settling to a steady state value.

12. A method for processing time staggered portions of an analog information signal for a signal path, comprising:

sampling the analog information signal at a plurality of phases;

measuring an equalization quality of the samples from one of the plurality of phases; and

equalizing the samples from each of the phases based on the measured equalization quality of the one phase, the equalizing including adjusting a difference between an average of post-transition sample amplitudes and an average of steady state sample amplitudes of the analog samples.

13. The method according to claim 12 further comprising:

quantizing the equalized analog samples.

19. The method of claim 12, wherein the post-transition sample amplitudes represent amplitudes of the equalized analog samples after transitioning from a first amplitude to a second amplitude before settling to a steady state value.

14. A system for processing a serial analog information signal, comprising:

a sampler configured to sample the serial analog information signal to generate analog samples;

an equalizer coupled to said sampler and configured to minimize inter-symbol interferences in the analog samples output from said sampler, said equalizer being configured to adjust a difference between an average of post-transition sample amplitudes and an average of steady state sample amplitudes of the analog samples to generate equalized samples; and

a quantizer coupled to said equalizer and configured to quantize said equalized samples output from said equalizer.

15. The system of claim 14, further comprising control logic coupled to a finite impulse response (FIR) filter in said equalizer, said control logic including:

a difference detector including a steady-state path, a post-transition path, and a combiner, wherein said combiner is configured to output an average difference between post-transition amplitudes of the equalized samples and steady-state amplitudes of the equalized samples; and

a state machine coupled to one or more outputs of said difference detector and configured to generate tap updates for said FIR filter according to said average difference.

16. The system according to claim 15, wherein said control logic further comprises:

a first input coupled to an output of said equalizer;

an analog-to-digital converter (ADC) coupled to said first input; and

a control module coupled to an output of said ADC, wherein

said ADC is configured to generate multi-level representations of equalized samples, and said control module is configured to generate said tap updates from at least said multi-level representations of the equalized samples.

17. The system according to claim 16, wherein said control logic further comprises:

a second input coupled to an output of said quantizer; and

a least-means-squared (LMS) module coupled to said first and second control logic inputs, wherein

said LMS module is configured to compare the multi-level representations of equalized samples with the quantized samples from said quantizer, and to generate said tap updates according to the comparison.

20. The system of claim 14, wherein the post-transition sample amplitudes represent amplitudes of the equalized analog samples after transitioning from a first amplitude to a second amplitude before settling to a steady state value.