Teledyne JTA2 User Manual
JTA2
Jitter & Timing Analysis
Operator’s Guide
December 2003
LeCroy Corporation
700 Chestnut Ridge Road
Chestnut Ridge, NY 10977–6499
Tel: (845) 578 6020, Fax: (845) 578 5985
Internet: www.lecroy.com
© 2003 by LeCroy Corporation. All rights reserved.
LeCroy, ActiveDSO, ProBus, SMART Trigger, JitterTrack, WavePro, WaveMaster, and
Waverunner are registered trademarks of LeCroy Corporation. Information in this publication
supersedes all earlier versions. Specifications subject to change without notice.
JTA2-OM-E Rev A
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ACCESSING JTA2...............................................................................................3
TIMING FUNCTIONS............................................................................................3
TIMING PARAMETERS........................................................................................4
Statistical Tools.................................................................................................................................4
HOW JITTERTRACK WORKS.............................................................................5
Using “Clock” or “Data” ....................................................................................................................5
WHEN TO USE JITTERTRACK...........................................................................7
JitterTrack or Trend? ................................................................................................................7
CLOCK OR DATA?..............................................................................................9
SETTING UP JITTER MEASUREMENTS..........................................................11
Jitter Math Setup............................................................................................................................11
JitterTrack...............................................................................................................................12
Jitter Parameters Setup .................................................................................................................12
WHEN TO USE PERSISTENCE HISTOGRAMS................................................14
SETTING UP PERSISTENCE HISTOGRAMS ...................................................15
Selecting the Math Function...........................................................................................................15
Setting Up the Histogram...............................................................................................................16
Selecting the Cut.....................................................................................................................16
HOW TO TRACE PERSISTENCE...................................................................... 17
An Innovative Visual and Processing Tool.....................................................................................17
To Set Up Trace Persistence..........................................................................................................18
CHOOSING A TIMING PARAMETER................................................................20
HOW TO USE THE TREND TOOL.....................................................................21
The Basic Idea ...............................................................................................................................21
To Set Up and Configure Trend .....................................................................................................22
Parameter Setup.....................................................................................................................22
Math Setup..............................................................................................................................24
HISTOGRAM AND TREND CALCULATION .....................................................25
Acquisition Sequence.....................................................................................................................25
Parameter Buffer............................................................................................................................25
Parameter Events Capture.............................................................................................................26
Zoom Traces and Segmented Waveforms.....................................................................................26
Histogram Peaks.....................................................................................................................26
Example..................................................................................................................................27
Binning and Measurement Accuracy......................................................................................27
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JTA2 Option
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ACCESSING JTA2
To access JTA2's special features, you must first purchase and install the option. Once installed,
JTA2's math and parameter selections will app ear in the Math and Measure menus.
TIMING FUNCTIONS
JitterTrack, PersistenceHistogram and PersistenceTrace are timing functions in LeCroy’s JitterPro
and JTA jitter and timing analysis packages. The JitterTrack feature is key to identifying the
source of excessive jitter or non-normal jitter characteristics. A timel ine of signal jitter that is
synchronous with the signal under test allows you to view patterns that would remain invisible
using other systems, zoom to areas containing maximum jitter, and troubleshoot the problem.
PersistenceHistogram is the ideal quantitative "companion" to persisten ce display. It histograms a
horizontal or vertical slice of the persistence waveform. Utilizing average, si gma, and range
settings, PersistenceTrace comp utes a vector trace from a bit map to give insight into edge
details down to a few picoseconds.
• JitterTrack graphically plots as a function of time the amplitude of the waveform
attributes Cycle-to-Cycle variation, Duty Cycle, Interval Error, Period, Width, and
Frequency. Interval Error, for example, calculates the timing error of a signal compared
with an ideal, expected interval defined by a user-specified reference frequency, the most
common estimator of jitter. "The sho rt-te rm variations of a digital signal’s significant
instants, from their ideal positions in time," are plotted. This is the perfect tool for
characterizing clocks in synchronized telecom networks such as SONET and SDH. A
special data function, available for most of these attributes, enables work on random data
streams.
• Persistence Histogram analyzes a vertical or horizontal slice of a persistence map of
multiple waveforms. The resultant bar chart shows a numerical measurement of the
timing variations of a signal, which are observed qualitatively in the persistence display of
the signal. A typical application is characterizing the jitter in a communications signal eye
diagram.
• Persistence Trace is a method for displaying the data acquired from multiple sweeps of
a waveform. A vector trace is computed, based on the bit map of the underlying multiple
signal acquisitions. Detail is then represented in a choice of three graphic forms, each
representing a different characteristic of the waveform. Insight into edge details is given
down to a few picoseconds — valuable in applications such as the examination of fast
signal transitions.
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JTA2 Option
TIMING PARAMETERS
Timing parameters can also be used to measure cycle-to-cycle jitter , the width of positive and
negative pulses, the duty cycle of either polarity, and an infinite number of cycles on long records.
Pulses or cycles can be counted using one of these parameters.
As interpolation filtering is applied to signal edges in the vicinity of measurement points, timing
parameters operate on acquired waveform levels that may be selected in either volts or
percentage of signal amplitude. Each parameter calculation is performed over all cycles or edges
present in the input signal, without limitations.
Statistical Tools
The information obtained from applying timing parame ters can then be analyzed using the
statistical tools, histograms and trends:
• Histograms characterize and present as a bar chart the statistical distribution of a timing
parameter’s set of values. In addition, there are 18 statistical histogram parameters,
which operate directly on the histogram.
• Trends represent the evolution of timing parameters in line graphs whose vertical axes
are the value of the parameter, and horizontal axes the order in which the values were
acquired.
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HOW JITTERTRACK WORKS
Using “Clock” or “Data”
Use this function to plot as a bar chart the evolution over time of this and five other waveform
attributes in simple steps.
How JitterTrack’s Interval Error works when “Clock” Mode is selected
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JTA2 Option
When “Data” Mode is selected.
1. Set the desired reference clock frequency for an ideal position against which the signal is
to be compared, or use “Find Frequency.”
2. Specify the level at which the jitter measurement is to be made, as well as the rising or
falling edge on which the measurement is to start.
3. Timing errors are graphically revealed.
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WHEN TO USE JITTERTRACK
The JitterTrack Function chart s the evolu t ion in time of these waveform attributes :
• Cycle-to-Cycle deviation
• Duty Cycle
• Interval Error
• Period
• Pulse Width
• Frequency
Each is time-correlated to its source trace and contains the same number of points as the
waveform.
JitterTrack or Trend?
Whether it is more appropriate to use JitterTrack or the statistical tool, Trend will largely depend
on the application, as well as the other factors set out in the tables below. While JitterTrack
sample points are evenly spaced in time, those of Trend are not. Trend plots any parameter
available in the instrument against its event count, as in a scatter or an XY diagram.
Characteristic Trend JitterTrack
Representation parameter Value vs. Events attribute value vs. time
Attributes or
Parameters Supported
Behavior cumulative over several
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all parameters Cycle-Cycle
Period
Duty Cycle
Width
Interval Error
Frequency
non-cumulative
acquisitions
up to 1 million events
(resets after every acquisiti on)
unlimited number of events
JTA2 Option
When you need to Use…
monitor the evolution of a waveform parameter
or attribute over several acquisitions...
time-correlate an event and a parameter value...
monitor an evolution in the frequency domain... JitterTrack - Trend points are not evenly
monitor JT A parameters...
Random NRZ (Non-Return to Zero) data stream and its corresponding clock signal.
Trend - Jitter works only on one acquisition at a
time
JitterTrack
spaced in time and therefore cannot be used
for FFT (Fast Fourier Transform).
Trend
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