SERDES Clock Recovery With Sync-Pulse Phase Error Correction
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Solution Overview
Problem
Conventional clock recovery systems in serial data communication are bulky, power-hungry, and lack fine resolution adjustability, making them unsuitable for high-speed data communication.
Innovation Solution
A method and system using a serializer/deserializer (SERDES) circuit to generate a clock signal that alternates between high and low output values, adjusting phase and frequency based on sync pulse intervals, with precise phase slip rates to synchronize with remote transmitters, minimizing jitter and resource usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional Phase Locked Loop (PLL) systems are used for clock recovery, then effective clock synchronization is achieved, but system size, weight, and power requirements increase
Solution Approach 1:
The patent replaces conventional analog PLL circuits with a digital clock recovery system that uses a Numerically Controlled Oscillator (NCO) implemented in software or digital logic. The NCO uses digital counters and phase accumulators to generate and adjust clock phases, eliminating the need for analog components like voltage-controlled oscillators and phase detectors, thereby reducing system size, weight, and power consumption while maintaining synchronization accuracy
Solution Approach 2:
The system dynamically adjusts clock recovery parameters including phase offset, frequency offset, and timing advance by modifying digital control words fed to the NCO. This allows the system to adapt to varying channel conditions and maintain accurate synchronization without requiring complex analog circuitry, thus reducing physical footprint while preserving reliability
2Measurement precision
If all-digital clock synthesis with delay elements is used, then fine timing resolution is achieved, but the system is limited to low-speed data communication
Solution Approach 1:
The patent implements a dynamic clock recovery system where the NCO continuously adjusts its output frequency and phase based on real-time error feedback from the received signal. The system can rapidly adapt to high-speed data rates by dynamically modifying its operation mode, switching between different timing adjustment granularities, and adjusting the update rate of the phase and frequency corrections to match the data rate being recovered
Solution Approach 2:
The digital clock recovery system is designed to handle multiple data rates and modulation schemes through a unified NCO architecture. By programmatically configuring the NCO parameters and using configurable delay elements, the same hardware platform can recover clocks for various speed requirements, from low-speed to high-speed serial communications, making it universally applicable rather than limited to specific data rates
3Reliability
If conventional clock recovery systems are implemented, then clock synchronization is achieved, but fine resolution adjustability is lacking
Solution Approach 1:
The system provides fine resolution adjustability by using digital control words to precisely set the NCO frequency and phase parameters. The phase accumulator can be configured with arbitrary resolution, allowing incremental phase adjustments in fine steps. Frequency tuning is achieved through programmable control words that determine the frequency tuning word (FTW), enabling precise frequency adjustments without the coarse limitations of analog PLLs
Solution Approach 2:
The clock recovery function is segmented into independent digital modules including phase detection, error filtering, frequency estimation, and NCO control. Each module can be independently configured and adjusted, allowing fine-tuned optimization of different aspects of clock recovery. This modular digital architecture enables precise control over phase and frequency adjustments with independent parameter optimization
Data Source
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AI summary
Clock recovery from a serial data signal involves using a serializer/deserializer (SERDES) to produce a clock signal which periodically alternates between high and low output clock values. These high and low clock values are generated by outputting for each clock period a series of N digital bits including a plurality of low-level bits to form each low output clock value and a plurality of high-level bits to form each high output clock value. A sync pulse obtained from a sync word present in each frame of the serial data signal is used to periodically determine a frequency error of the clock signal. The frequency error is used as a basis to change a phase of the adjusted clock signal responsive to the frequency error.