Adaptive noise filtering and equalization for optimal high speed multilevel signal decoding

• US 7,573,966 B2
• Filed: 02/21/2006
• Issued: 08/11/2009
• Est. Priority Date: 07/15/2002
• Status: Expired due to Fees

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Quellan, Inc. (Renesas Electronics Corporation)
• Inventors: Kim, Andrew Joo, Bajekal, Sanjay, Hietala, Vincent Mark
• Primary Examiner(s): Fan; Chieh M
• Assistant Examiner(s): Ghulamali; Qutbuddin
• Application Number:
  US11/358,901
• Publication Number:
  US 20060239390A1
• Time in Patent Office: 1,267 Days
• Field of Search: 375/350, 375/355, 375/357, 375/358, 375/344, 375/316, 375/317, 375/219, 398/202, 370/201, 370/286
• US Class Current: 375/350
• CPC Class Codes: H04L 2025/03363 Multilevel H04L2025/03369 takes precedence
• CPC Class Codes: H04L 2025/03471 Tapped delay lines H04L2025/03464 takes precedence
• CPC Class Codes: H04L 25/03076 not using decision feedback
• CPC Class Codes: H04L 25/03267 with decision feedback equalisers

Abstract

A Signal Conditioning Filter (SCF) and a Signal Integrity Unit (SIU) address the coupled problem of equalization and noise filtering in order to improve signal fidelity for decoding. Specifically, a received signal can be filtered in a manner to optimize the signal fidelity even in the presence of both significant (large magnitudes of) ISI and noise. The present invention can provide an adaptive method that continuously monitors a signal fidelity measure. Monitoring the fidelity of a multilevel signal can be performed by external means such as by the SIU. A received signal y(t) can be “conditioned” by application of a filter with an electronically adjustable impulse response g(t). A resulting output z(t) can then be interrogated to characterize the quality of the conditioned signal. This fidelity measure q(t) can be used to adjust the filter response to maximize the fidelity measure of the conditioned signal.

Claims

1. A system for processing digital signals comprising symbols propagated according to a period, the system comprising:

a signal conditioning filter comprising;

a first stage for mitigating degradations of the digital signals that occur according to a first time scale, the first stage comprising a first analog filter tuned to the first time scale, the first time scale comprising a fraction of the period at which the symbols are propagated, and

a second stage for removing signal distortions that occur according to a second time scale, the second stage comprising a second analog filter tuned to the second time scale, the second time scale being different than the first time scale and comprising a magnitude at least equal to the period at which the symbols are propagated; and

a signal integrity unit coupled to an output of the second stage, the signal integrity unit comprising a third analog filter stage for producing an analog probability estimate, the signal integrity unit analyzing the analog probability estimate and adjusting the first and second time scales based on the analysis of the analog probability estimate.

2. The system of claim 1, wherein each analog filter comprises a linear tapped-delay line filter.

3. The system of claim 2, wherein each linear tapped delay-line filter comprises LC circuits.

4. The system of claim 1, wherein the signal integrity unit controls the signal conditioning filter by maximizing fidelity of the digital signals.

5. The system of claim 1, wherein the signal conditioning filter comprises a coefficient amplifier, the coefficient amplifier comprising a Gilbert cell multiplier.

6. A system for processing digital signals comprising symbols propagated according to a symbol period, the system comprising:

a first analog filter stage comprising a first filter tuned to a first time constant, the first time constant comprising a value that is less than the symbol period, for compensating for signal distortions that occur within a single symbol period and for integrating over less than a symbol period;

a second analog filter stage comprising a second filter tuned to a second time constant, the first time constant being smaller than the second time constant and the second time constant comprising value at least equal to the symbol period; and

a signal integrity unit coupled to an output of the second analog filter stage, the signal integrity unit comprising a third analog filter stage for producing an analog probability estimate, the signal integrity unit analyzing the analog probability estimate and adjusting the first and second time constants based on the analysis of the analog probability estimate.

7. The system of claim 6, wherein each filter comprises linear tapped-delay line filter.

8. The system of claim 6, wherein each filter comprises a coefficient amplifier, the coefficient amplifier comprising a Gilbert cell multiplier.

9. The system of claim 6, wherein the first filter stage substantially reduces at least one of ringing, jitter, and noise.

10. The system of claim 6, wherein the second filter stage removes inter-symbol interference (ISI).