Frequency-Domain Equalization Circuit for Wraparound Distortion Control
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Solution Overview
Problem
Existing adaptive frequency domain filters in optical fiber communication require significant calculation resources for coefficient updates, and the constraint methods to prevent distortion from block wraparound increase the calculation load, while methods that ignore distortion do not effectively address the issue.
Innovation Solution
Implement a frequency domain filter with an overlap-save method, adaptive coefficient updating, and a constraint operation unit that applies constraints at a lower frequency than coefficient updates to minimize calculation load while suppressing distortion from block wraparound.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If adaptive frequency domain filter coefficient updates are performed frequently to maintain equalization performance, then equalization accuracy is improved, but calculation amount and processing time increase significantly
Solution Approach 1:
The patent applies periodic action by updating filter coefficients at specific intervals rather than continuously. The coefficient updating unit performs updates based on predetermined conditions (such as signal quality thresholds or time intervals), transforming the continuous adaptation process into discrete periodic operations. This reduces the total number of calculations while maintaining effective equalization performance.
Solution Approach 2:
The patent implements dynamics by making the update frequency adaptive rather than fixed. The system adjusts the coefficient update rate dynamically based on signal conditions, channel stability, and performance metrics. When the transmission path is stable, updates occur less frequently; when conditions change, updates increase in frequency, optimizing the balance between accuracy and processing load.
2Reliability
If constraint operations are applied to prevent block wraparound distortion, then signal quality is improved, but calculation amount increases
Solution Approach 1:
The patent applies preliminary action by performing constraint operations in advance before the actual signal processing. The constraint operation unit prepares and applies constraints to the frequency domain filter coefficients beforehand, preventing block wraparound distortion from affecting the output signal. This proactive approach eliminates the need for more complex corrective operations during signal processing.
Solution Approach 2:
The patent extracts and isolates the constraint operation from the main signal processing flow. By separating the constraint application into a dedicated unit that operates independently on filter coefficients, the system minimizes the computational burden on the main signal processing path. Only the necessary constraint calculations are performed, rather than applying constraints to every signal sample.
3Productivity
If frequency domain filtering is used to handle large time spread, then calculation amount is reduced compared to time domain filtering, but block wraparound distortion is introduced
Solution Approach 1:
The patent introduces an intermediary constraint operation unit between the frequency domain filter and the output signal. This intermediary component applies constraints to the filter coefficients to prevent block wraparound distortion from propagating to the output. The constraint operation unit acts as a mediator that maintains the computational efficiency of frequency domain filtering while eliminating the harmful distortion effect.
Data Source
AI summary
A frequency domain filter receives an input signal in a frequency domain being blocked by an overlap-save method. The frequency domain filter multiplies the input signal in the frequency domain by a coefficient for each frequency. A coefficient updating unit adaptively updates a filter coefficient of the frequency domain filter. A constraint operation unit performs an operation of a constraint on a filter coefficient of the frequency domain filter in such a way as not to be affected by distortion caused by wraparound from both ends of a block to the output signal. A frequency at which the constraint operation unit performs the operation of the constraint is lower than a frequency at which the coefficient updating unit adaptively updates the filter coefficient of the frequency domain filter.