Cross-Domain Time Stamp Generation Without Quantization Noise
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Solution Overview
Problem
Existing electronic systems face challenges in generating accurate time stamps, particularly when transitioning signals between clock domains, as quantization noise is introduced, affecting the precision and synchronization of temporal measurements in applications like financial networks and network traffic analysis.
Innovation Solution
The techniques involve using a filter to remove quantization noise from timing references when coupling between clock domains, ensuring that the time stamps are both accurate and synchronized with the clock signal, employing methods such as phase locked loops and discrete time circuits to produce precise time stamps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a timing reference signal is coupled between clock domains, then synchronization between domains is achieved, but quantization noise is introduced degrading measurement precision
Solution Approach 1:
The time stamping function is segmented into two independent parts: MSBs generated in the first clock domain using the clean timing reference, and LSBs generated in the second clock domain using the recovered clock. This segmentation allows each part to operate in its optimal clock domain without introducing quantization noise into the other, thereby maintaining both synchronization and precision.
Solution Approach 2:
A phase interpolator is introduced as an intermediary device between the two clock domains. It takes the timing reference from the first clock domain and the recovered clock from the second clock domain, and generates a phased version of the timing reference that is synchronized to the second clock domain without introducing quantization noise. This intermediary enables precise time stamping across clock domain boundaries.
2Measurement precision
If quantization noise is filtered from the timing reference, then time stamp precision is improved, but additional filtering circuitry increases device complexity
Solution Approach 1:
The phase interpolator serves as an intermediary that avoids the need for explicit quantization noise filtering. By generating a phased timing reference that is inherently synchronized to the second clock domain, it eliminates quantization noise at the source rather than requiring additional filtering circuitry to remove it later.
Solution Approach 2:
The patent replaces traditional filtering mechanisms with a phase interpolation approach. Instead of using filters to remove quantization noise from the timing reference, the system uses phase interpolation to generate a clean, synchronized timing signal directly, substituting a more elegant signal processing technique for conventional filtering.
Data Source
AI summary
Embodiments of the present disclosure include techniques for generating accurate time stamps. In one embodiment, a first timing reference signal corresponding to a first clock domain is combined with a first clock signal corresponding to a second clock domain to produce a second timing reference signal that includes quantization noise. The second timing reference signal is filtered to remove the quantization noise and generate a filtered timing reference signal. The filtered timing reference signal may be sampled in the second clock domain to obtain a time stamp. In one embodiment, a phase locked loop (PLL) is used as the filter. The PLL may generate first and second ramps that correspond to time. One of the ramps may be sampled to obtain a time stamp, for example.