Adaptive CDR Loop Gain Control for Jitter Tolerance
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Solution Overview
Problem
Conventional clock and data recovery (CDR) circuits face issues with varying jitter and high transition density, leading to frequent changes in loop bandwidth, which affect their performance and jitter tolerance.
Innovation Solution
The CDR circuit incorporates a bang-bang phase detector, digital filter, and adaptive loop gain control (ALGC) circuit to detect loop bandwidth variations and adjust the proportional and integral path gain factors, using either a bang-bang or linear adjusting method to maintain optimal loop bandwidth and enhance jitter tolerance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a bang-bang phase detector is used to generate phase difference information, then the CDR circuit can operate with simple structure, but the loop bandwidth varies frequently due to different gain from varying jitter
Solution Approach 1:
The patent implements dynamic adjustment of the loop bandwidth by using an adaptive loop gain control circuit that modifies the proportional and integral path gain factors in real-time based on detected bandwidth variations. This allows the CDR circuit to adapt to changing jitter conditions while maintaining stable operation, resolving the contradiction between simple structure and bandwidth stability.
Solution Approach 2:
The patent introduces a feedback mechanism where the adaptive loop gain control circuit continuously monitors the loop bandwidth and adjusts the gain factors accordingly. This feedback loop compensates for bandwidth variations caused by jitter, maintaining stable CDR performance without increasing overall system complexity.
2Productivity
If the input data has high transition density, then more data information can be transmitted, but significant change in bandwidth occurs affecting CDR performance
Solution Approach 1:
The adaptive loop gain control dynamically adjusts the proportional and integral path gain factors in response to bandwidth variations caused by high transition density data. This allows the system to maintain stable loop bandwidth even when processing high-speed data streams with frequent transitions, enabling both high productivity and bandwidth stability.
3Stability of the object's composition
If the loop bandwidth is kept fixed, then the CDR circuit operates stably, but it cannot adapt to varying jitter and transition density conditions
Solution Approach 1:
The patent implements a dynamic loop bandwidth adjustment mechanism through the adaptive loop gain control circuit, which modifies the proportional and integral path gain factors based on real-time detection of bandwidth variations. This enables the CDR circuit to adapt to varying jitter and transition density conditions while maintaining stable operation, effectively resolving the contradiction between fixed stability and adaptive versatility.
Data Source
AI summary
A clock and data recovery circuit with jitter tolerance enhancement is provided. The CDR circuit includes: a bang-bang phase detector, a digital filter, a digitally controlled oscillator, and an adaptive loop gain control circuit. The CDR circuit detects a loop bandwidth variation and adjusts the loop bandwidth of CDR circuit by adjusting proportional path and integral path gain factors of the digital filter of the CDR circuit. The loop gain controller uses two methods to adjust the loop gain in CDR circuit: bang-bang adjusting method and linear adjusting method.