Equalizer Tap Adaptation for Sampling Phase Recovery
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Solution Overview
Problem
In communications systems, the clock recovery process is interfered with by clock delay corrections from adaptive equalization, leading to suboptimal sampling phases and increased noise in the timing recovery loop.
Innovation Solution
An equalizer that detects and controls clock delay corrections by dynamically adjusting tap weights based on Center of Filter (COF) offsets, minimizing interference with the timing recovery loop and optimizing sampling phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive equalization is used to correct channel distortion and time delays, then equalization performance is improved, but clock delay correction interferes with the timing recovery process causing sampling phase shifts
Solution Approach 1:
The patent separates the equalization adaptation function from the timing recovery function by extracting and compensating for clock delay corrections. The equalizer adapts tap weights for equalization while the timing recovery loop independently recovers clock timing, preventing interference between the two processes.
Solution Approach 2:
The patent implements a feedback mechanism where the Center of Filter (COF) value, which indicates clock delay correction amount, is continuously monitored and used to adjust equalizer tap weights. This feedback loop enables the system to compensate for clock delay corrections and maintain optimal sampling phases despite equalization adaptation.
2Adaptability or versatility
If equalizer tap weights are dynamically adapted to time-variant channel characteristics, then adaptability to channel changes is improved, but clock delay correction increases interfering with timing recovery
Solution Approach 1:
The patent converts the harmful clock delay correction by the equalizer into a useful signal. The COF value, which represents the amount of clock delay correction, is extracted and fed back to adjust equalizer tap weights, thereby compensating for the interference while maintaining the benefits of adaptive equalization.
Solution Approach 2:
The COF value serves as an intermediary parameter that mediates between the equalization process and the timing recovery process. It carries information about clock delay corrections from the equalizer and enables compensation without directly interfering with the timing recovery loop.
Data Source
AI summary
System and method of timing recovery to achieve sampling phase optimization with aid of equalization adaptation. For equalizer filter, the offset between a current Center of Filter (COF) value and a nominal COF value is used as a measure for a clock phase correction resulted from an adaptive equalization process. A COF may be defined as a function of two selected tap weights or equal to a selected tap weight. The nominal COF value can be dynamically adapted based on the real-time sampling phase error. The tap weights of the equalizer filter are adjusted to decrease the offset, e.g., by interpolating/extrapolating selected tap weights based on the offset. By using sampling phase error as a feedback for COF_nom updating and so for equalization adaptation, the clock delay correction contributed by the adaptive equalization process is advantageously controlled to benefit sampling phase optimization.