Split-Loop Timing Recovery for Frequency Offset and Jitter Tracking
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Solution Overview
Problem
High-speed communication systems face challenges in timing recovery due to integral and differential nonlinearity issues in phase interpolators and limited bandwidth in delta-sigma modulation approaches, particularly in achieving precise frequency offset compensation and jitter tracking.
Innovation Solution
A split loop timing recovery system that separates frequency offset tracking using delta sigma modulation and random jitter tracking using a phase interpolator, with bandwidth partitioning between these paths to effectively manage non-idealities and improve timing recovery accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single loop architecture is used for timing recovery, then the system structure is simple, but it cannot simultaneously achieve accurate frequency offset compensation and jitter tracking due to bandwidth limitations
Solution Approach 1:
The single timing recovery loop is segmented into two separate loops: a frequency offset tracking loop and a jitter tracking loop. Each loop is optimized for its specific function with appropriate bandwidth characteristics, allowing simultaneous accurate frequency offset compensation and jitter tracking without the conflicts present in a single loop architecture
2Measurement precision
If delta-sigma modulation is used for frequency offset tracking, then frequency offset compensation is achieved, but the tracking bandwidth is limited
Solution Approach 1:
The bandwidth limitation of delta-sigma modulation is addressed by segmenting the timing recovery function into two separate loops. The frequency offset tracking loop uses delta-sigma modulation for accurate low-bandwidth tracking, while the jitter tracking loop operates at higher bandwidth to compensate for the limited tracking speed, achieving both accuracy and speed requirements
3Measurement precision
If phase interpolator based timing recovery is used, then timing accuracy is improved, but integral and differential nonlinearity issues arise
Solution Approach 1:
The harmful nonlinearity errors of phase interpolators are mitigated by segmenting the timing recovery into separate functional loops. The frequency offset tracking loop handles the bulk of timing adjustments, reducing the burden on the phase interpolator and minimizing nonlinearity effects. The jitter tracking loop then refines timing accuracy with minimal impact from nonlinearity errors
Data Source
AI summary
Various embodiments provide systems and methods for performing clock recovery on a received signal using a split loop architecture. A split loop timing recovery apparatus is provided comprising a first path configured for performing frequency offset tracking on a signal by adjusting a receiver clock frequency to match a remote transmitter frequency associated with the signal and a second path configured for tracking random jitter on the signal.