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

• US 20100040180A1
• Filed: 08/11/2009
• Published: 02/18/2010
• Est. Priority Date: 07/15/2002
• Status: Active Grant

• Current Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Original Assignee: Intersil Americas LLC (Renesas Electronics Corporation)
• Inventors: Hietala, Vincent Mark, Kim, Andrew Joo, Bajekal, Sanjay
• Granted Patent: US 8,311,168 B2
• Time in Patent Office: Days
• US Class Current: 375/348
• 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

1-32. -32. (canceled)

33. A method for processing digital signals comprising a series of symbols and a symbol period with first signal degradation on a first time scale and second signal degradation on a second time scale, the method comprising the steps of:

mitigating the first signal degradation with a first filter configured to the first time scale;

mitigating the second signal degradation with a second filter configured to the second time scale;

producing a probability estimate in response to processing an output of the first filter or the second filter; and

adjusting the first time scale for the first filter or the second time scale for the second filter based on the probability estimate,

wherein the first time scale is less than the symbol period and the second time scale is greater than the symbol period.

34. The method of claim 33, wherein the first filter comprises a first analog filter and the second filter comprises a second analog filter.

35. The method of claim 33, wherein the probability estimate comprises an analog probability estimate.

36. The method of claim 33, wherein the adjusting step comprises adjusting the first time scale and the second time scale based on the probability estimate.

37. The method of claim 33, wherein the first signal degradation comprises ringing or jitter and wherein the second signal degradation comprises inter-symbol interference.

38. The method of claim 33, wherein the first filter comprises a first linear tapped-delay line filter, and wherein the second filter comprises a second a linear tapped-delay line filter.

39. The method of claim 33, wherein the symbol period specifies a time interval spanning between two temporally adjacent symbols in the series of symbols.

40. The method of claim 33, wherein the digital signals are communication signals.

41. A method for processing a digital signal comprising signal distortions, the method comprising the steps of:

processing the digital signal with a plurality of filters arranged in series, each filter filtering according to a respective filtering parameter;

producing a probability estimate in response to processing an output of one of the filters; and

adjusting each of the filtering parameters according to the probability estimate.

42. The method of claim 41, wherein the probability estimate comprises an analog probability estimate.

43. The method of claim 41, wherein the plurality of filters comprises a first filter that feeds a second filter, and wherein producing the probability estimate comprises processing an output of the second filter with a third filter.

44. The method of claim 43, wherein the signal distortions comprise first signal distortions occurring substantially within a symbol period of the digital signal and second signal distortions occurring beyond the symbol period,

wherein the first filter is operative to compensate for the first signal distortions, and

wherein the second filter is operative to compensate for the second signal distortions.

45. The method of claim 41, wherein a first filter in the series of filters reduces ringing, jitter, or noise of the digital signal.

46. The method of claim 45, wherein the first filter in the series of filters feeds a second filter in the series of filters, and wherein the second filter reduces inter-symbol interference (ISI) of the digital signal.

47. The method of claim 41, wherein the digital signal comprises a communication signal.

48. The method of claim 41, wherein each filter in the plurality of filters comprises a respective coefficient amplifier that comprises a Gilbert cell multiplier.

49. A method for processing a digital signal comprising the steps of:

reducing ringing, jitter, or noise on the digital signal in response to processing the digital signal with a first filter stage having a first time constant;

reducing inter-symbol interference on the digital signal in response to processing the digital signal with a second filter stage having a second time constant;

generating a probability estimate from an output of the first filter stage or the second filter stage; and

refining the first time constant and the second time constant based on an analysis of the probability estimate.

50. The method of claim 49, wherein the first filter stage feeds the second filter stage, and wherein the generating step comprises generating the probability estimate from an output of the second filter stage.

51. The method of claim 49, wherein the first time constant is below a symbol period of the digital signal.

52. The method of claim 51, wherein the second time constant is above the symbol period.