Phase Detector Clock Calibration for Phase Offset Reduction
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Solution Overview
Problem
Phase detectors in data communication systems face large phase offsets due to process and temperature variations, and the optimal phase sampling point varies with different optical components and fiber lengths, leading to increased bit error rates.
Innovation Solution
The solution involves adjusting the phase of sampling clocks and error clocks using transition count differences and filtering techniques to minimize phase offsets and automatically determine the optimal sampling phase, utilizing integrated circuits with phase detectors, filters, and phase interpolators to generate error signals and adjust clock phases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear phase detector is used to determine optimal phase sampling point, then phase detection capability is provided, but large phase offsets occur that change with process and temperature
Solution Approach 1:
The patent implements feedback by counting data transitions during calibration, comparing the count to a target value, and using the difference to adjust the phase of error clocks and sampling clock. This closed-loop feedback mechanism eliminates systematic phase offsets by continuously monitoring transition counts and adjusting phases until the optimal sampling point is achieved, thereby resolving the contradiction between phase detection capability and phase offset stability
Solution Approach 2:
The patent changes the phase parameter of error clocks and sampling clock based on transition count measurements. By adjusting the phase parameter dynamically during calibration and operation, the system adapts to process and temperature variations, maintaining reliable phase detection despite environmental changes
2Device complexity
If phase sampling is performed at a fixed point, then simple sampling is achieved, but optimal phase sampling point varies with different optical components and fiber lengths leading to increased BER
Solution Approach 1:
The patent makes the sampling system dynamic by automatically adjusting the phase of the sampling clock based on transition count measurements. Instead of using a fixed sampling point, the system dynamically adapts the sampling phase to match the optimal point for each specific optical system configuration, thereby reducing BER without requiring complex manual calibration for each component variation
Solution Approach 2:
The system performs self-calibration by automatically measuring transition counts and adjusting its own sampling phase without external intervention. The calibration circuitry within the receiver autonomously determines the optimal sampling point by monitoring transition counts and adjusting phases accordingly, enabling the system to adapt to different optical components and fiber lengths independently
3Measurement precision
If transition counting is performed to estimate BER, then error rate measurement is achieved, but phase calibration complexity increases
Solution Approach 1:
The patent makes the transition counting mechanism serve multiple functions: it simultaneously estimates BER and provides calibration information for phase adjustment. By using the same transition count data for both error rate measurement and phase optimization, the patent avoids adding separate calibration circuits, thereby reducing overall system complexity while maintaining accurate BER estimation
Data Source
AI summary
In one embodiment, the present invention includes a system having an amplifier to receive an incoming signal and a recovery circuit coupled to the amplifier that includes a phase detector to adjust a phase of a sampling clock via a signal indicative of a difference between transitions occurring between the sampling clock and each of a first error clock and a second error clock. Based on a phase adjusted output of the phase detector, the sampling clock may be generated with an appropriate phase. Thus, circuitry and methods are provided to reduce or eliminate phase offsets in the phase detector.