Clock Jitter & Phase Noise Measurement and Analysis
Precision & AccuracyPrecision & Accuracy
Clock Jitter ToolsetClock Jitter Toolset
Phase NoisePhase Noise
Serial Data JitterSerial Data Jitter
Clock Data Jitter Clock Data Jitter
ResourcesResources
Clock jitter analysis showing phase noise analysis and random and deterministic separation of clock jitter, showing phase noise to jitter comparison

Measure and Eliminate Clock Jitter in Digital Circuits

In-circuit clock signals need to be highly accurate and stable to ensure proper circuit operation. Clock jitter, phase noise and other distortions must be understood and minimized to ensure the circuit operates at its maximum potential. Common measurements made using oscilloscopes include:

  • Clock jitter, n-cycle jitter, accumulated jitter
  • Phase noise measurements, phase noise to jitter correlation
  • Spread spectrum clocking analysis
  • Low-frequency jitter and wander measurements
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Highest Precision and Most Sophisticated Clock Jitter Analysis

Teledyne LeCroy's Clock Expert software, used with a compatible Teledyne LeCroy oscilloscope, is the most precise and sophisticated tool for measuring clock jitter, phase noise, and accumulated jitter, including very low frequency (<5 Hz) jitter.

Screen capture of clock jitter analysis and phase noise analysis using a one millisecond clock signal capture for time jitter to phase noise correlation

Highest Precision Clock Signal Captures

  • 12 bits resolution all-the-time ensures high precision measurements
  • Long capture times measure very low frequency jitter
  • High quality oscilloscope sample clock for low additive jitter
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Screen capture with clock jitter noise reduction tools improving the accuracy of clock jitter versus time measurements

Improve Measurement Accuracy with Unique Noise Reduction Tools

  • Heterodyne signal mixing reduces noise on low slew-rate clock signals
  • Dual-input method provides additional noise reduction
  • Flexible input bandwidth filtering further optimizes SNR of clock signal
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Clock signal acquisition to measure clock jitter for multiple jitter measurements

Most Versatile and Efficient Clock Jitter Measurement Toolset

  • Most consistent measurements
  • Faster and more efficient analysis
  • Most complete toolset
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Clock Expert Overview

Clock Expert software screen image showing complete clock jitter measure and clock phase noise analysis
  • Jitter Separation Track:
    Display jitter track of jitter separation parameter (TIE, Period, Half Period, Cycle-to-Cycle). This view of jitter quickly detects bursted jitter and modulation.
  • Jitter Separation Histogram:
    This view of jitter quickly displays whether jitter aggressors are causing non-Gaussian distributions or long tails.
  • Jitter Separation Parameters:
    Total jitter (Tj) can be separated into deterministic jitter (Dj) and random jitter (Rj). Dj is further decomposed into periodic and data-dependent components (Pj, DDj, ISI, DCD)
  • Phase Noise:
    Phase noise display shows the phase noise variation/jitter in the frequency range. Supports up to 20 markers and RMS phase jitter determination.
  • Measurements with Track and Histogram:
    Up to 12 measurement parameters can be displayed simultaneously as a track function and/or as a histogram.
  • Measurements Table:
    Up to 12 measurements can be calculated simultaneously and displayed in a table including statistical information.
  • Accumulated Jitter Analysis:
    The cumulative jitter (N-cycle jitter) shows the long-term jitter. The accumulated jitter can be calculated for peak and standard deviation for N up to 10000.
  • Accumulated Jitter Parameter:
    Showing the minimum and maximum value of the accumulated jitter graphs.
  • Graphical User Interface:
    The graphical user interface contains easy-to-understand icons and simplifies the setup.
  • Status Bar:
    In the status bar, important information, warnings and error messages are displayed.

Highest Precision Clock Signal Captures

Teledyne LeCroy oscilloscopes have the best signal acquisition hardware and the longest acquisition memory for both the highest precision acquisitions and extended clock jitter analysis capabilities.

Teledyne LeCroy HD4096 technology triad showing combination of high SNR input amplifiers, high sample rate 12-bit ADCs and a low noise system architecture

12 Bits All the Time Ensures High Precision Measurements

Only Teledyne LeCroy provides 12 bits of vertical resolution without compromises for best signal to noise ratio and lowest intrinsic jitter – achieve unmatched jitter measurement precision.

  • No tradeoff of resolution, sample rate, or bandwidth
  • Best signal-to-noise ratio for lowest intrinsic jitter
  • Lowest noise for unmatched jitter measurement precision

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Clock jitter measurement showing low frequency jitter (wander) to 5 Hz with phase noise analysis for phase noise to jitter correlation

Long Capture Times Measure Very Low Frequency Jitter

Teledyne LeCroy oscilloscopes have the industry's longest acquisition memory with capability to perform math analysis on the largest acquisitions. This provides capability to analyze the lowest frequency jitter components.

  • Measure wander to 5 Hz or less
  • Measure jitter caused by 50/60 Hz power line issues
  • View low frequency jitter and wander variation over time
Clock jitter analysis using an oscilloscope with very low sample clock jitter

High Quality Oscilloscope Sample Clock

Teledyne LeCroy oscilloscopes use the highest quality sample clocks to minimize additive jitter from the measurement system to the clock signal acquisition.

  • Ensures low additive jitter from measurement system
  • Sample clock jitter as low as 15 fsRMS

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Unique Noise Reduction Tools Further Improve Measurement Accuracy

Further improve your measurement accuracy by using the unique noise reduction, measurement and filtering tools provided in Clock Expert

  • Heterodyne signal mixing reduces noise on low slew-rate clock signals
  • Dual-input method provides additional noise reduction
  • Flexible input bandwidth filtering further optimizes SNR of clock signal
Screen capture showing clock jitter time interval error measurement versus time with noise reduction applied to improve measurement accuracy

Most Versatile and Efficient Clock Jitter
Measurement Toolset

The Clock Expert analysis architecture provides the most consistent measurements in the fastest, most efficient way. Clock Expert also contains the most complete clock jitter measurement toolset.

Screen capture showing clock jitter time interval error measurement versus time with noise reduction applied to improve measurement accuracy

Most Consistent Clock Jitter Measurements

Use Teledyne LeCroy's long oscilloscope memory to take one long clock signal acquisition and make all clock jitter measurements and phase noise analysis on the same set of data, using a single, consistent setup.

  • All measurements are made with one clock signal acquisition
  • Global settings are uniformly applied to ensure setup consistency
  • Ultra-long memory permits simultaneous measurement of low and high-frequency jitter
Clock Expert user interface images

Faster and More Efficient Clock Jitter Analysis

Save time and use one software option that includes all the clock jitter and phase noise measurement tools you need, and perform all analyses with an easy-to-use graphical user interface.

  • One software option has all the required measurement tools
  • Simplified user setup – no confusing wizards
  • No need for multiple acquisitions
Screen capture of clock signal with simultaneous multiple jitter measurements, phase noise analysis, jitter separation, statistical distributions, and spectral analysis.

Most Complete Clock Jitter Measurement Toolset

Get more insight and analyze jitter in any domain. View all the measurements and analysis views simultaneously in one software option.

  • Complete jitter domain analysis - time, frequency (spectral and phase noise) and statistical
  • Many different simultaneous jitter measurements and views

Most Complete Clock Jitter and Phase Noise Measurement Toolset

Get more insight and analyze jitter in any domain. View all the measurements and analysis views simultaneously in one software option.

Screen capture of clock signal with simultaneous multiple jitter measurements, statistical distributions, and jitter versus time
Screen capture of clock signal time interval error jitter calculation and plot versus time, jitter separation, and jitter spectral analysis.
Phase noise analysis of clock signal using oscilloscope, with phase noise to jitter correlation in table
Screen capture of accumulated n-cycle jitter calculation using an oscilloscope
Screen capture showing spread spectrum clocking modulation of clock spread spectrum signal

Measurements

Rj and Dj separation

Phase Noise

Accumulated Jitter

SSC Analysis

View all the jitter measurements at one time with the corresponding jitter vs. time (Track) and statistical (Histogram) views in one easy-to-use setup.

  • Configurable measurement table display
  • 12 simultaneous clock jitter measurements with simultaneous Track and Histogram views
  • Easy-to-use setup

Get the most complete determination of total jitter and Rj+Dj jitter separation for time interval error (TIE) jitter and many more clock jitter measurements

  • TIE, Half-Period, Period, Cycle-to-Cycle and N-Cycle jitter separation
  • Jitter results as time domain (Track), Jitter FFT, Histogram or Bathtub curve

Expand jitter view to frequency domain using Phase Noise Analysis

  • Ultra long memory support for lowest phase noise frequency
  • RMS phase noise jitter calculation
  • Multi-cursor and table view
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Gain more insight about jitter over long periods of time with Accumulated (N-cycle) Jitter Analysis

  • Fast calculation
  • Unmatched graphical representation
  • Table display of all essential measurements

Validate your EMC requirements with Spread Spectrum Clock (SSC) Modulation Analysis.

  • Specialized measurements for SSC analysis
  • Quick and easy verification that SSC modulation is within design specifications

Phase Noise and Time Jitter Measurements Using an Oscilloscope

An oscilloscope can provide phase noise measurements and correlate phase noise to clock jitter measurements. The accuracy and range of the phase noise measurement is dependent on the oscilloscope sample clock jitter, noise performance and acquisition memory length.

Phase noise vs. frequency plot with correlation to jitter in table, using an oscilloscope

How is Jitter and Phase Noise Measured?

The short-term stability of an oscillator is characterized by measuring the jitter in the time domain and the phase noise in the frequency domain. Both measurements describe the same underlying phenomena. Therefore, it is possible to correlate phase noise to jitter.

A phase noise analyzer only measures in the frequency domain whereas an oscilloscope measures in the time domain but can mathematically convert this data to the frequency domain. Therefore, an oscilloscope is ideal for measuring both jitter and phase noise. However, the oscilloscope must have high performance to meet the measurement needs of modern oscillators.

The measurement of phase noise with an oscilloscope is based on the measurement of the TIE (Time Interval Error). The TIE measurement is a time (or unit interval) difference between the time at which an input signal exceeds a preset voltage threshold and the ideal time location of a user-specified reference frequency. TIE measurements are usually plotted in time units as a function equal to a set of measurements over a period of time, which is a graphical display of the phase modulation envelope of the oscillator. This can be mathematically converted by the oscilloscope to a frequency-domain plot of phase noise vs. frequency.

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Phase noise vs. frequency plot with correlation to jitter in table, using an oscilloscope and showing cursors on phase noise plot

Calculating Time Jitter from Phase Noise

Once a plot of phase noise vs. frequency is generated, the equivalent RMS value of the TIE jitter can be calculated from the integrated phase noise power over the frequency range of interest. Cursors are used to define the frequency range on the phase noise plot, and jitter and phase noise values are displayed in a table.

    Phase noise vs. frequency plot showing comparison with noise reduction techniques applied

    High Performance Oscilloscopes and Noise Reduction Tools Improve Phase Noise Calculation Accuracy

    Teledyne LeCroy's 12-bit oscilloscopes combine low noise (high signal-to-noise ratio performance) with extremely low internal sample clock jitter. This results in a very low jitter noise floor. However, jitter (and phase noise) performance can be enhanced further with the heterodyne function, filters and the dual input method.

    • Heterodyne Function: The heterodyne function uses a software approach based on the operation of a phase noise analyzer and is ideal for signals with a low slope.
    • Input Filter: High-frequency noise and unwanted effects from the measurement setup can have a negative influence on the measurements. These effects can be reduced by using suitable low-pass, high-pass or band-pass filters to reduce extraneous noise.
    • Dual Input Method: This method splits the measurement signal externally via a splitter to acquire it simultaneously through two input channels in the oscilloscope. The noise in the two input channels is not coherent, and therefore the signal-to-noise ratio is increased.
    Block diagram of phase noise analyzer measurement process

    Heterodyne Function in Clock Expert Performs a Similar Function to a Phase Noise Analyzer

    A typical phase noise measurement with a spectrum analyzer or phase noise analyzer is shown in the figure on the left. The output signal of the oscillator under test is mixed with the output signal of a reference oscillator with low phase noise, which is set to the same frequency and a relative phase of 90°. The phase shift is set to exact phase quadrature, which is indicated by a minimum DC level at the output of the mixer. The mixer now works as a phase detector and generates a voltage that is proportional to the phase difference between the two sources. The reference oscillator has a very low phase noise and the output of the mixer is essentially a function of the phase noise of the oscillator under test. The output signal of the mixer is low-pass filtered to remove the higher-frequency sum terms and the spectral components of the mixer leakage.

    The heterodyne function in Clock Expert works on the same principle, using a software approach, with the reference oscillator generated internally in software and assumed to be ideal.

    A long oscilloscope acquisition memory with low frequency phase noise (wander) calculated down to 20 Hz

    Low-frequency Phase Noise Analysis Using Oscilloscope Long Acquisition Memory

    The phase noise measurement in an oscilloscope uses a fast-fourier transform (FFT) to convert time-domain data to the frequency domain. The lowest frequency that can be calculated with an FFT is the inverse of the acquisition period, and the acquisition period (at a given sample rate) is defined by the oscilloscope acquisition memory length with more memory equating to a lower measured frequency.

    For example, to be able to measure phase noise at a frequency of 20 Hz, the acquisition period must be 50 milliseconds (1/.050 seconds = 20 Hz). 50 milliseconds captured with a sampling rate of 10 GS/s requires 500 million points (Mpts) of oscilloscope acquisition memory (.050 s * 10e9 S/s = 500e6 S, or points).

    Most Complete Serial Data Analysis Toolbox

    Teledyne LeCroy’s SDA Expert Serial Data Analysis options provide all the tools you need for any high-speed serial data NRZ or PAM eye diagram, jitter, or noise measurement.

    • Most Complete Serial Data Analysis Toolbox
    • Highest confidence for complex measurements
    • Tailored technology analysis for PCI Express, USB, Thunderbolt, DisplayPort, and more
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    SDA Expert serial data analysis NRZ eye diagram, jitter histogram, jitter track, jitter FFT and random, deterministic and total jitter measurements
    Basic jitter analysis of clock signal using JITKIT software package

    Basic Toolbox for Clock and Clock-Data jitter

    JitKit is a basic, easy-to-use jitter analysis tool that meets the requirements for fast analysis of clock and clock-to-data jitter. It is specifically designed for the needs of embedded system designers.

    • Fast and easy validation
    • Direct display of jitter values
    • Four views of jitter speeds debug and analysis
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    Resources

    Technical Docs

    Videos

    Name
    Clock Expert Datasheet

    		Datasheet
    Clock Expert Software Instruction Manual

    		Product Manual
    The difference between Edge-to-Reference and Edge-to Edge “JITTER” analysis Technical Brief

    		Read App Note
     
    Clock Expert Overview – Measuring Phase Noise and Clock Jitter

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