CDR PLL Behavioral Simulation for Jitter and PPM Phase Alignment
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Solution Overview
Problem
Current simulation models for clock-data recovery (CDR) phase-locked loops (PLLs) face challenges in accurately and efficiently simulating complex features like jitter and parts-per-million (PPM) errors, requiring a tradeoff between simulation complexity and runtime, and struggle to model mixed-signal components with analog transitions in a continuous time domain while maintaining system-level abstraction and accuracy.
Innovation Solution
A simulation model that filters data and reference clock signals to remove jitter and PPM errors, using a threshold function to adjust the reference clock signal and calculate lag, and applies a delay to align the signals, while continuously updating the prediction model to account for noise and errors, allowing for fast and accurate simulation of CDR PLL behavior.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If simulation models include complex features like jitter and PPM errors, then measurement precision improves, but simulation runtime increases
Solution Approach 1:
The patent extracts and models only the essential characteristics of jitter and PPM errors that significantly impact CDR PLL performance, rather than simulating all noise components. This selective extraction maintains measurement precision for critical parameters while reducing overall simulation complexity and runtime.
Solution Approach 2:
The patent transforms complex noise characteristics into simplified parameter representations (e.g., statistical parameters for jitter, frequency offset parameters for PPM errors). This parameter transformation enables accurate modeling of error effects without requiring full-time-domain simulation of all noise components, thus reducing runtime while preserving measurement precision.
2Device complexity
If simulation models use discrete events, then device complexity reduces, but ability to model analog transitions worsens
Solution Approach 1:
The patent introduces intermediary models that bridge discrete event simulation and continuous analog behavior. These intermediaries (such as statistical models for jitter accumulation and analytical models for PPM effects) allow discrete event simulators to accurately represent analog transitions without requiring full continuous-time simulation, thus maintaining both simplicity and reliability.
3Ease of operation
If simulation models provide system-level abstraction, then ease of operation improves, but measurement precision worsens
Solution Approach 1:
The patent applies different levels of modeling detail to different parts of the CDR PLL system. Critical components (phase detector, loop filter, VCO) use detailed models that preserve measurement precision, while less critical aspects use higher-level abstractions. This local differentiation maintains ease of operation for system-level analysis while preserving precision where needed for accurate performance prediction.
Data Source
AI summary
Method and non-transitory computer-readable medium storing instructions for simulating a phase-locked loop measures a first phase of a data signal and a second phase of a reference clock signal in a phase-locked loop to be simulated, filters the first phase of the data signal by a threshold function of a lock detection module of the phase-locked loop to be simulated, and adjusts the second phase of the reference clock signal to align with the filtered first phase of the data signal.