Fast Equalization for Jitter Mitigation in Serial Links
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Solution Overview
Problem
Existing communication systems struggle to mitigate high-frequency jitter, which affects receiver performance, especially at high data rates, as timing recovery loops can only track jitter frequencies below their bandwidth.
Innovation Solution
A fast equalization system that includes a filter, slicer, lookup table, and coefficient improvement module, which uses updated filtering coefficients to reduce jitter effects beyond the timing recovery bandwidth, compatible with existing clock recovery methods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a timing recovery loop is used to track jitter, then jitter at frequencies below the loop bandwidth is mitigated, but jitter at frequencies above the loop bandwidth cannot be tracked and deteriorates receiver performance
Solution Approach 1:
The patent divides jitter mitigation into two separate functional segments: a timing recovery loop that handles low-frequency jitter (below loop bandwidth) and a fast equalization module that handles high-frequency jitter (above loop bandwidth). This segmentation allows each module to optimize for its specific frequency range without compromise, resolving the contradiction between reliability for low-frequency jitter and adaptability for high-frequency jitter.
Solution Approach 2:
The fast equalization module acts as an intermediary between the timing recovery loop and the slicer, specifically addressing the high-frequency jitter component that the timing recovery loop cannot handle. This intermediary module processes the equalized signal to further reduce high-frequency jitter before slicing, enabling comprehensive jitter mitigation across the entire frequency spectrum.
2Reliability
If the timing recovery loop bandwidth is increased to track higher frequency jitter, then more jitter frequencies are mitigated, but the loop becomes less stable and more complex
Solution Approach 1:
Instead of increasing the timing recovery loop bandwidth to handle high-frequency jitter, the patent segments the jitter mitigation function into two independent modules: the original timing recovery loop for low-frequency jitter and a new fast equalization module for high-frequency jitter. This avoids the complexity and stability issues that would arise from broadening the loop bandwidth while achieving comprehensive jitter coverage.
3Measurement precision
If conventional equalization is used to compensate for channel distortions, then signal quality is improved, but high-frequency jitter effects remain and degrade performance
Solution Approach 1:
The fast equalization module serves as an intermediary processing stage between the conventional equalizer and the slicer. It specifically targets and mitigates high-frequency jitter components that pass through the conventional equalizer unaffected, thereby eliminating the harmful high-frequency jitter impact while preserving the signal quality improvements achieved by conventional equalization.
Solution Approach 2:
The patent replaces the traditional timing-recovery-dependent jitter mitigation mechanism with a new fast equalization mechanism that operates independently of the timing recovery loop bandwidth. This substitution enables high-frequency jitter mitigation without being constrained by the timing recovery loop's frequency response characteristics.
Data Source
AI summary
A system for receiving signals transmitted via serial links includes an equalizer for accessing a digitized communications signal and producing an equalized output signal, and a fast equalization module for determining output data corresponding to the communications signal. The fast equalization module includes a filter to access an output of the equalizer, a slicer module to access an output of the filter and produce a data output corresponding to the communications signal, a lookup table to provide filtering coefficients to the filter, and a coefficient improvement module to improve the coefficients based on an error signal from the filter. The coefficient improvement module is configured to update the coefficients in the lookup table.