CT-Delta-Sigma Jitter Measurement via SNR Degradation
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Solution Overview
Problem
Existing methods for detecting and measuring clock jitter in high-frequency clock signals require precise external reference clock signals, which are not feasible for all applications.
Innovation Solution
A circuit using a continuous time Delta-Sigma modulator with a jitter injection mechanism to perturb a single tone signal, allowing for the detection of clock jitter through signal-to-noise ratio analysis without an external reference clock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a precise external reference clock signal is used for jitter measurement, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The system uses its own internal clock signal as the reference for jitter measurement, eliminating the need for external reference equipment. The continuous-time delta-sigma modulator processes the clock signal itself, and the processing circuit extracts jitter information from the output data, allowing the system to self-diagnose clock jitter without external aids
Solution Approach 2:
The continuous-time delta-sigma modulator acts as an intermediary that converts the clock signal into a form where jitter information can be extracted. The modulator's output data serves as a mediator that contains encoded jitter information, which the processing circuit then decodes to measure jitter characteristics
2Measurement precision
If a precise external reference clock signal is used for jitter measurement, then measurement precision is improved, but ease of operation deteriorates
Solution Approach 1:
The measurement system operates autonomously using internal resources. The clock signal under test is fed into the continuous-time delta-sigma modulator, which processes it and generates output data containing jitter information. The processing circuit automatically extracts jitter metrics from this data, eliminating the need for operators to set up external reference equipment or perform complex calibration procedures
3Ease of operation
If continuous-time delta-sigma modulator is used for jitter detection, then ease of operation is improved, but measurement precision may deteriorate
Solution Approach 1:
The system exploits the relationship between the modulator's output parameters and the input clock signal characteristics. By analyzing specific parameters in the output data (such as spectral components or statistical properties), the processing circuit can accurately extract jitter information. The continuous-time delta-sigma modulator's inherent noise shaping and signal processing characteristics are leveraged to preserve jitter information in the output
Solution Approach 2:
The continuous-time delta-sigma modulator employs feedback mechanisms that enhance its sensitivity to clock jitter. The feedback loop within the modulator structure creates a system where jitter in the clock signal produces measurable effects in the output data, allowing the processing circuit to detect and quantify jitter with high precision
Data Source
AI summary
A continuous time Delta-Sigma (CT-ΔΣ) modulator has an input node configured to receive an input signal and an output node configured to output a digital output signal. The CT-ΔΣ modulator includes a feedback loop with a summation circuit configured to sum the digital output signal with a jitter perturbed test signal to generate a signal supplied to an input of a digital to analog converter circuit. A single tone signal is injected with a jitter error of a clock signal to generate the jitter perturbed test signal. A processing circuit processes the digital output signal to detect a signal to noise ratio of the CT-ΔΣ modulator. The detected signal to noise ratio is indicative of presence of jitter in the clock signal.