Clock Recovery Loop Bandwidth Tuning for Jitter Measurement
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-speed communication systems face challenges in clock recovery due to non-ideal edge detection in clock recovery units, leading to degraded measurements and variability across different signal types and test instrumentation.
Innovation Solution
A controller is used to adjust the loop bandwidth of a clock recovery unit by instructing it to provide a recovered clock at different loop bandwidth settings, comparing measurements, and applying adjustments to minimize tracking of deterministic spectral components while maintaining proper tracking of random jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a relatively higher loop bandwidth is used in the clock recovery unit, then the ability to respond to timing variations and track random jitter is improved, but deterministic spectral components related to data patterns are tracked causing measurement degradation
Solution Approach 1:
The patent segments the clock recovery process into two distinct phases: a first measurement phase using a first loop bandwidth setting, and a second measurement phase using a second loop bandwidth setting. This segmentation allows each phase to capture different aspects of signal characteristics without the interference that occurs when a single bandwidth setting is used for both purposes.
Solution Approach 2:
The patent changes the loop bandwidth parameter between measurement phases. By switching between different loop bandwidth settings, the system can optimize for either random jitter tracking or deterministic component rejection depending on the current measurement phase, thereby resolving the contradiction between these two requirements.
2Measurement precision
If a lower loop bandwidth is used to reduce tracking of deterministic components, then measurement improvements are achieved, but less random jitter of the transmitter clock is tracked degrading results
Solution Approach 1:
The patent divides the measurement process into separate phases, each using appropriate loop bandwidth settings. The first phase uses a bandwidth optimized for one aspect of measurement, while the second phase uses a bandwidth optimized for another aspect, allowing both requirements to be met through temporal separation.
Solution Approach 2:
The patent employs periodic switching between different loop bandwidth settings in different measurement phases. This periodic action allows the system to alternate between capturing random jitter characteristics and rejecting deterministic components, achieving both goals through time-multiplexed operation.
3Measurement precision
If physical parameters of the clock rate recovery are adjusted to reduce deterministic component tracking, then variability across test instrumentation is reduced, but the process is time-consuming and expensive
Solution Approach 1:
The patent changes operational parameters (loop bandwidth settings) rather than adjusting physical parameters of the hardware. This software-controlled parameter switching achieves measurement consistency across different instrumentation without requiring time-consuming physical adjustments or calibration procedures.
Solution Approach 2:
The patent makes the loop bandwidth dynamic and adjustable during operation, allowing the system to adapt to different measurement requirements in real-time. This dynamic approach eliminates the need for static hardware adjustments and enables rapid switching between measurement modes.
Data Source
AI summary
A controller includes a memory, a processor, and a first interface to a clock recovery unit that provides a recovered clock. When executed by the processor, instructions from the memory cause the controller to: instruct, via the first interface, the clock recovery unit at a first loop bandwidth to provide the recovered clock to a signal sampler; instruct, via the first interface, the clock recovery unit at a second loop bandwidth wider than the first loop bandwidth, to provide the recovered clock to the signal sampler; compare measurements from the signal sampler at the first loop bandwidth to measurements from the signal sampler at the second loop bandwidth; and instruct, via the first interface, the clock recovery unit at a third loop bandwidth to provide the recovered clock to the signal sampler applying adjustments based on comparing the measurements.