Equalizer Tap Weight Segmentation for Timing Recovery Interference
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Solution Overview
Problem
In communication systems, the interaction between adaptive equalization and timing recovery loops leads to undesirable clock delay corrections, impairing the equalizer's ability to track channel changes, as conventional methods like freezing equalizer adaptation impede its capability to adapt to time-varying channel characteristics.
Innovation Solution
An equalizer that detects and compensates clock delay corrections by dynamically adjusting tap weights based on the Center of Filter (COF) value, preventing interference with the timing recovery loop, allowing for continuous adaptation to channel changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If adaptive equalization is continuously adapted to track channel changes, then the equalizer can maintain equalization performance, but it introduces unwanted clock delay correction that interferes with timing recovery
Solution Approach 1:
The patent segments the equalizer tap weights into two distinct groups: tracking tap weights that adapt to channel changes, and timing-related tap weights that are adjusted to compensate for COF shifts. This segmentation allows the equalizer to maintain its tracking capability while separately managing the timing interference issue through selective adaptation of different tap weight subsets.
Solution Approach 2:
The patent introduces COF (Center of Filter) offset as an intermediary parameter that measures the timing interference caused by adaptive equalization. By monitoring and compensating for COF offset through specific tap weight adjustments, the system mediates between the need for continuous equalization adaptation and the requirement to prevent timing recovery interference.
2Object-generated harmful factors
If equalizer adaptation is frozen or slowed down to prevent timing recovery interference, then clock delay correction interference is reduced, but the equalizer loses its capability to track channel changes
Solution Approach 1:
The patent implements dynamic adaptation where different tap weights are updated at different rates and with different purposes. Tracking tap weights continuously adapt to channel variations, while timing-related tap weights are dynamically adjusted based on COF offset measurements. This dynamic approach allows the system to maintain both tracking capability and timing recovery compatibility simultaneously.
Solution Approach 2:
The patent changes the adaptation parameters selectively: tracking tap weights undergo continuous adaptation to follow channel changes, while timing-related tap weights are adjusted based on COF offset measurements. This selective parameter change strategy enables the equalizer to adapt to channel variations without introducing unwanted timing corrections that would interfere with the timing recovery loop.
3Reliability
If COF-based compensation is applied to eliminate timing interference, then timing recovery performance is improved, but the system complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the COF offset is continuously calculated from the equalizer tap weights and used to adjust the timing-related tap weights. This feedback loop automatically compensates for timing interference without requiring complex external control systems, as the compensation is generated internally based on the equalizer's own state.
Solution Approach 2:
The equalizer performs self-compensation for timing interference by using its own tap weight information to calculate COF offset and automatically adjusting its timing-related tap weights. This self-service approach eliminates the need for separate timing correction mechanisms, reducing overall system complexity while improving timing recovery performance.
Data Source
AI summary
System and method of timing recovery for recovering a clock signal with reduced interference with clock phase correction by an adaptive equalizer. The equalizer in the timing recovery loop is dynamically adapted to the current channel characteristics that vary over time. The equalizer includes compensation logic operable to detect and compensate a correction of clock phase ascribed to the equalization adaptation. The compensation logic can calculate the offset between a center of filter (COF) value and a COF nominal value, the offset indicative of the amount and direction of clock phase correction contributed by the equalizer. Based on the offset, the compensation logic adjusts the equalized signal by adjusting the tap weights of the equalizer to correct the offset, thereby compensating the clock phase correction.