Burst-Mode CDR Clock Alignment Using Data-Detected Phase Switching
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Solution Overview
Problem
In GPON networks, the clock data recovery (CDR) circuit struggles to maintain accurate phase and frequency alignment during burst mode transmission, particularly when dead times have intermediate durations, leading to phase and frequency drift of output clock signals.
Innovation Solution
A circuit comprising a phase detector, phase frequency detector, data detection circuit, multiplexer, and clock signal generation circuit that dynamically switches between lock-to-reference and lock-to-data modes based on data detection, using a phase-locked loop and voltage-controlled oscillator to adjust clock signals, ensuring accurate phase and frequency alignment with a reference clock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the CDR circuit switches to lock-to-reference mode during dead time, then phase and frequency alignment is maintained, but the switching requires sufficient time to align which causes performance degradation during intermediate dead times
Solution Approach 1:
The patent applies preliminary action by maintaining the lock-to-data mode during intermediate dead times instead of switching to lock-to-reference mode. This prevents the need for time-consuming phase and frequency alignment operations during dead time, thereby avoiding performance degradation while still maintaining adequate synchronization through the previously established lock state
Solution Approach 2:
The patent implements dynamics by conditionally determining whether to switch modes based on dead time duration. For intermediate dead times (125-250 nanoseconds), the circuit dynamically maintains lock-to-data mode rather than switching to lock-to-reference mode, adapting the operation mode to the specific timing conditions to optimize performance
2Device complexity
If the CDR circuit remains in lock-to-data mode during long dead times, then switching complexity is reduced, but phase and frequency drift occurs leading to performance degradation
Solution Approach 1:
The patent applies segmentation by dividing dead time into different duration categories (short, intermediate, long) and applying different mode strategies to each segment. For long dead times exceeding 250 nanoseconds, the circuit switches to lock-to-reference mode to maintain accuracy, while using lock-to-data mode for shorter durations, thereby segmenting the problem to optimize both complexity and reliability
3Measurement precision
If the CDR circuit switches modes frequently to maintain alignment, then clock signal accuracy is maintained, but system complexity and switching overhead increase
Solution Approach 1:
The patent applies local quality by applying different mode strategies to different dead time duration scenarios rather than using a uniform approach. The control logic evaluates dead time length and applies the appropriate mode (lock-to-data or lock-to-reference) locally to each dead time event, optimizing the balance between accuracy and complexity for each specific condition
Data Source
AI summary
A circuit includes a phase detector circuit, a phase frequency detector circuit, a data detection circuit, a multiplexer circuit, and a clock signal generation circuit. The phase detector circuit is operable to generate a first phase detection signal based on a data signal and a first periodic signal. The phase frequency detector circuit is operable to generate a second phase detection signal based on second and third periodic signals. The data detection circuit is operable to generate a data detection signal based on the first phase detection signal. A multiplexer circuit is operable to provide one of the first and the second phase detection signals as a selected signal based on the data detection signal. The periodic signal generation circuit is operable to cause adjustments to phases of the first and the second periodic signals based on the selected signal.