Receiver Clock Phase Detection Using Interior Spectral Components
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Solution Overview
Problem
In optical communication networks, clock phase noise due to jitter in sample timing relative to symbol timing reduces the accuracy of symbol estimates at the receiver, and existing clock recovery methods are affected by signal degradation from chromatic dispersion, polarization mode dispersion, and amplified spontaneous emission, leading to suboptimal clock phase detection.
Innovation Solution
A method at the receiver apparatus involves calculating an estimate of phase offset through cross-correlation of a first sequence of values with a representation of the communications signal, using a complex conjugate operation and frequency-dependent weighting, allowing for clock phase detection even with reduced signal excess bandwidth and energy in roll-off regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional clock recovery methods are used, then clock phase detection can be performed, but accuracy is reduced due to signal degradation from chromatic dispersion, polarization mode dispersion, and amplified spontaneous emission
Solution Approach 1:
The patent converts the harmful effects of signal degradation (chromatic dispersion, polarization mode dispersion, amplified spontaneous emission) into a beneficial framework by using frequency-dependent weighting that specifically targets and utilizes interior spectral components. Instead of being misled by degraded roll-off regions, the method transforms the degraded signal into useful phase offset information through selective frequency domain processing and cross-correlation with weighted interior spectral components.
2Use of energy by moving object
If roll-off regions are used for clock phase detection, then sufficient signal energy is available, but spectral efficiency is reduced and hardware complexity increases
Solution Approach 1:
The patent extracts and utilizes only the useful interior spectral components for clock phase detection, separating them from the problematic roll-off regions. By applying frequency-dependent weighting that emphasizes interior components and de-emphasizes roll-off regions, the method extracts phase offset information from the most reliable parts of the spectrum, achieving accurate clock recovery without relying on energy from roll-off regions.
Solution Approach 2:
The patent transitions from time-domain or conventional frequency-domain analysis to a weighted frequency-domain approach that distinguishes between different spectral regions. By introducing frequency-dependent weighting as an additional dimension of processing, the method can selectively access interior spectral components while ignoring degraded roll-off regions, thereby improving spectral efficiency.
3Measurement precision
If conventional clock recovery methods are used, then clock phase can be detected, but hardware complexity and heat generation increase
Solution Approach 1:
The patent segments the frequency spectrum into interior spectral components and roll-off regions, applying different processing strategies to each segment. By dividing the frequency domain processing into weighted interior component analysis and de-emphasized roll-off region handling, the method reduces the computational burden compared to processing the entire spectrum uniformly, thereby reducing hardware complexity.
4Measurement precision
If sample timing has jitter relative to symbol timing, then clock phase noise occurs, but maintaining precise timing alignment increases system complexity
Solution Approach 1:
The patent introduces frequency-dependent weighting as an intermediary processing step between signal reception and clock phase detection. This intermediary operation in the frequency domain facilitates robust phase offset estimation by filtering out timing jitter effects through selective weighting of interior spectral components, simplifying the overall timing alignment process.
Data Source
AI summary
A receiver apparatus comprises circuitry configured for storing a first sequence of values. At the receiver apparatus, a communications signal is received which conveys a second sequence of values, the second sequence of values being related to the first sequence of values. According to some examples, the second sequence of values is identical to the first sequence of values. At the receiver apparatus, P results are calculated from a cross-correlation of the first sequence of values with at least a portion of a representation of the communications signal, where P is a positive integer. According to some examples, P≥2. An estimate of a phase offset of a continuous clock is calculated as a function of the P results. According to some examples, the function is a non-linear function. The estimate of the clock phase offset may be used to achieve clock recovery at the receiver apparatus.