Digital Clock Recovery Loop for Fast Frequency Capture
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing CDR circuits face issues with slow frequency acquisition time and limited capture range, leading to data loss and reduced recoverable data rates.
Innovation Solution
A CDR apparatus and method that includes a frequency detector to generate continuous frequency up and down signals, and a digital loop filter for coarse and fine adjustments, minimizing frequency acquisition time and ensuring harmonic lock prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the CDR circuit uses traditional frequency detection and adjustment methods, then the circuit structure remains simple, but the frequency acquisition time is slow and data loss occurs
Solution Approach 1:
The patent segments the frequency adjustment process into three distinct stages: coarse adjustment stage using CFDN/CFUP signals for rapid frequency correction, intermediate adjustment stage for moderate frequency corrections, and fine adjustment stage using FH/FL signals for precise frequency matching. This segmentation allows the system to apply different adjustment strategies appropriate to the magnitude of frequency deviation, thereby reducing overall acquisition time while preventing data loss through systematic frequency alignment
Solution Approach 2:
The patent implements dynamic switching between different adjustment modes based on real-time frequency detection results. The system dynamically transitions between coarse, intermediate, and fine adjustment stages, and between hold mode and adjustment mode, optimizing the frequency acquisition process adaptively. This dynamic approach enables fast initial frequency capture followed by progressive refinement, minimizing both acquisition time and data loss risk
2Adaptability or versatility
If the CDR circuit extends the capture range to recover more data rates, then the adaptability improves, but the complexity of the frequency detection and adjustment mechanism increases
Solution Approach 1:
The patent divides the frequency detection and adjustment mechanism into modular functional blocks: frequency detector, digital loop filter, coarse adjustment generator, and fine adjustment generator. Each module handles a specific aspect of frequency alignment, making the overall complex system manageable and maintainable. The segmentation allows independent optimization of each module while achieving extended capture range through their coordinated operation
Solution Approach 2:
The frequency detector is designed to universally detect various frequency relationships (FH, FL, FUH signals) across different data rates, and the digital loop filter universally processes different adjustment signals (CFDN, CFUP, FH, FL) through a single unified structure. This multi-functionality enables the system to handle a wide capture range without requiring separate specialized circuits for each frequency scenario, thus extending adaptability while controlling complexity
3Speed
If the CDR circuit uses fast frequency acquisition methods, then the frequency alignment speed improves, but the risk of harmonic lock increases
Solution Approach 1:
The patent implements preliminary frequency alignment through coarse adjustment using CFDN/CFUP signals before proceeding to fine adjustment with FH/FL signals. This preliminary action rapidly brings the clock frequency close to the target frequency, establishing a foundation for subsequent precise alignment. By pre-positioning the frequency in the correct range, the system achieves fast initial alignment while setting the stage for reliable harmonic lock prevention in the fine adjustment stage
Solution Approach 2:
The patent employs continuous feedback through the frequency detector that monitors the relationship between input data rate and clock frequency throughout the adjustment process. The detector provides real-time feedback signals (FH, FL, FUH) that inform the digital loop filter and adjustment generators about the current frequency alignment status. This feedback mechanism enables the system to detect and correct potential harmonic lock conditions while maintaining fast alignment speed through adaptive response
Data Source
AI summary
Proposed is an apparatus for a digital clock and data recovery. The apparatus includes a frequency detector for detecting a high frequency (FH) signal, a low frequency (FL) signal and ultra-high frequency (FUH) signal by determining the relationship between an input data rate and a clock frequency, and generating a continuous frequency up (CFUP) signal and a continuous frequency down (CFDN) signal based on the FH, FL and FUH signals; and a digital loop filter (DLF) for controlling to adjust a clock frequency in a coarse adjustment stage using the CFUP and CFDN signals and to adjust a clock frequency in a fine adjustment stage using the FH and FL signals.