Jitter Frequency Response Measurement via Clock Recovery
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Solution Overview
Problem
Measuring jitter frequency in high-speed digital systems is challenging due to varying data rates and types of jitter, which affect timing margins and system stability, especially in telecommunications and high-bandwidth interconnections.
Innovation Solution
A method involving a clock recovery circuit, counter, memory, frequency divider, and phase-locked loop to recover a clock signal, count it over a selected time period, and compare it to a reference signal to calculate the frequency of the recovered clock signal, enabling accurate measurement of jitter frequency response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If jitter is measured at high transmission rates (1-10 Gb/s), then timing margins become less tolerant to jitter, but measurement accuracy is improved
Solution Approach 1:
The patent segments jitter measurement into different frequency components using spectral analysis. By dividing the jitter spectrum into discrete frequency bins and analyzing each separately, the system can accurately measure jitter at high transmission rates while identifying which specific frequency components contribute most to timing errors, thereby maintaining timing margin tolerance through targeted correction.
Solution Approach 2:
The patent introduces an intermediary measurement approach that uses spectral density analysis as a mediator between the high-speed data stream and the jitter measurement process. This intermediary technique allows accurate jitter characterization at 1-10 Gb/s rates by transforming the time-domain jitter signal into the frequency domain, where it can be measured and analyzed without directly impacting the timing margins of the original signal.
2Adaptability or versatility
If multiple types of jitter (random, periodic, DDJ) are measured simultaneously, then comprehensive jitter characterization is achieved, but measurement complexity increases
Solution Approach 1:
The patent employs dynamic measurement techniques that adapt the analysis method based on the detected jitter characteristics. The system dynamically adjusts the spectral analysis parameters and measurement windows to optimize for the specific type of jitter being measured, whether random, periodic, or data-dependent. This dynamic adaptation allows comprehensive jitter type coverage while managing system complexity through intelligent, context-aware measurement strategies.
Solution Approach 2:
The patent changes measurement parameters such as frequency resolution, time window duration, and spectral analysis methods based on the detected jitter characteristics. By dynamically adjusting these parameters, the system can efficiently measure different jitter types (random, periodic, DDJ) using optimized settings for each type, thereby achieving comprehensive jitter characterization without requiring equally complex measurement systems for all jitter types simultaneously.
3Loss of information
If digital patterns with higher frequency content are analyzed, then more jitter information is obtained, but signal attenuation and phase shift increase
Solution Approach 1:
The patent replaces direct time-domain measurement of high-frequency jitter components with frequency-domain spectral analysis. Instead of attempting to directly measure and preserve attenuated high-frequency signals in the time domain, the system transforms the signal to the frequency domain where attenuated components can be identified, quantified, and compensated for through spectral density calculations, thereby recovering complete jitter information without being limited by signal attenuation.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for precise characterization of jitter frequency content, improving system stability and performance by accurately tracking and separating different frequency components of jitter, even in high-speed serial electrical backplanes.
Implementation Method 1
A method of measuring jitter frequency response includes recovering a clock signal from a data input stream to provide a recovered clock signal
Implementation Method 2
counting the recovered clock signal over a selected time period to provide a recovered clock count
Data Source
AI summary
A method of measuring jitter frequency response includes recovering a clock signal from a data input stream to provide a recovered clock signal and counting the recovered clock signal over a selected time period to provide a recovered clock count. A reference signal is counted over the selected time period to provide a reference signal count. The recovered clock count is compared to the reference signal count and a frequency of the recovered clock signal for the selected time period is calculated.