Clock Recovery Phase Offset Adjustment for Variable Data Frequency
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Solution Overview
Problem
Conventional clock recovery systems face errors due to insufficient timing margin when receiving data signals with varying frequencies, as they fail to accurately adjust the clock signal edge position in response to changes in high-frequency and low-frequency data signals, leading to potential errors during signal receipt.
Innovation Solution
A clock recovery system that includes a phase comparator to compute the position of transition edges, an edge counter to count transitions, and a controller to generate control signals that adjust the phase of the modulated clock signal based on the comparison results and transition edge counts, ensuring the clock signal edge is positioned appropriately relative to the data signal eye center, regardless of frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the clock recovery system uses a fixed phase adjustment method based on average phase detection, then the system structure remains simple, but timing margin becomes insufficient when data signal frequency changes
Solution Approach 1:
The patent implements dynamic phase adjustment by introducing an edge counter that tracks the number of transition edges in the data signal. Based on the counted edges, the system dynamically selects different phase adjustment amounts (first adjustment amount for high frequency, second adjustment amount for low frequency), making the clock phase modulator adaptive to frequency changes rather than using a fixed phase adjustment method.
Solution Approach 2:
The system changes the phase adjustment parameter based on the data signal frequency characteristics. By counting transition edges and comparing against a reference value, the system determines whether to apply a larger or smaller phase adjustment amount, effectively changing the modulation parameter to match the operating conditions and maintain optimal timing margin.
2Reliability
If the system adjusts clock phase dynamically based on transition edge count, then jitter tolerance improves, but device complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the edge counter continuously monitors transition edges in the data signal, and this information feeds back to the clock phase modulator. The phase adjustment amount is determined based on the feedback from edge counting, creating a closed-loop system that automatically compensates for frequency variations and improves jitter tolerance.
Solution Approach 2:
The system uses the data signal itself to generate the control information needed for phase adjustment. By counting transitions in the incoming data signal, the system self-determines the appropriate phase correction without requiring external control signals or complex calibration procedures, making the complexity manageable.
3Ease of operation
If the clock edge is positioned at the center of the data signal eye, then the system operates simply at low frequencies, but errors occur during high-frequency data reception
Solution Approach 1:
The patent applies different phase adjustment strategies for different frequency conditions. Instead of using a uniform center-positioning approach, the system applies a larger phase adjustment amount when high frequency is detected (more than a certain number of transitions) and a smaller adjustment amount when low frequency is detected, creating localized optimization for different operating conditions.
Data Source
AI summary
A clock recovery system includes a sampler that is configured to sample an input data signal in synchronization with a modulated clock signal to generate a sample of the input data signal. A phase comparator is configured to compute a position of a transition edge of the input data signal using the sample data signal, and to compare the computed position with a position of an edge of the modulated clock signal to generate a comparison result. An edge counter is configured to count transition edges of the sample data signal. A controller is configured to generate first and second control signals based on the comparison result and the count of the transition edges. A clock phase modulator is configured to generate the modulated clock signal by adjusting a phase of an input clock signal responsive to the first and second control signals, such that the phase is increased in response to the first control signal and reduced in response to the second control signal.