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Keysight Technologies
Pulse Parameter Denitions
Application Note
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Introduction
Electrical pulses are used to synchronize, trigger or control multiple electrical devices in a test
system. Pulses are also used for clock generation or radar testing. In order to describe a pulse
and make its creation repeatable, a set of parameters has been dened. This document describes
and illustrates all main pulse parameter denitions. It is a collection of terms used in the test and
measurement environment. The information will help the reader to understand the nature of a
pulse, and will make instrument specications comparable amongst each other.
External
trigger signal
Trigger
output
Output
Trigger
delay
Pulse
delay
Pulse period
Pulse
width
Transition
times
Double pulse
output
Channel A
output
Channel B
output
Figure 1. Overview of the pulse parameters
Double pulse delay
Delay A
Interchannel
delay skew
Delay B
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Time Reference Point
0%
50%
100%
Median
The time reference point is at the median of the amplitude (50% amplitude
point on pulse edge).
100%
Figure 2. Time reference at median amplitude
Figure 3. Pulse period
50%
Median
0%
Pulse Period
The time interval between the leading edge medians of consecutive
output pulses.
50%
Pulse period
Trigger Delay
Figure 4. Trigger delay
Interval between trigger point of the external trigger input signal and the
trigger output pulse’s leading-edge median.
External
trigger signal
Trigger
delay
Trigger
output
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Figure 5. Pulse width
Pulse Width
Interval between leading- and trailing-edge medians. The specified and displayed
value is that obtained with fastest edges, essentially equal to the interval from
the start of the leading edge to the start of the trailing edge. By designing so that
the pulse edges turn about their start points, the interval from leading-edge start
stays unchanged (in practice, start points may shift with changes in transition
time) when transition times are varied. This is more convenient for programming
and the width display is easy to interpret.
50%
Specified
width
Pulse Levels
Pulse output is specified as pulse top and pulse base (usually referred to as high
level and low level), or as peak to peak amplitude and median offset. A “window”
specification shows the limits within which the pulse can be positioned.
Figure 6. Pulse levels
Amplitude
Low level
High level
Zero volts
Median
Max high level
Offset
Min low level
Window
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Pulse Delay
50%
Specified
width
Interval between leading edge medians of trigger output pulse and output pulse.
The specified and displayed value is that obtained with the fastest leading edge.
Pulse delay has two components, a fixed delay from trigger output to output
signal and a variable delay with respect to the trigger output.
Trigger
output
Output
signal
Figure 7. Pulse delay
Figure 8. Double pulse delay
Fixed delay
Variable delay
Double Pulse Delay
Interval between leading edge medians of the double pulses.
Double pulse delay
Interchannel Delay (Skew)
Figure 9. Interchannel delay
Interval between corresponding leading-edge medians of the output signals.
Channel A
output
Interchannel
delay skew
Channel B
output
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Figure 10. Transition time
Double pulse delay
Transition Time
Interval between the 10%- and 90%- amplitude points on the leading/trailing edge.
100%
90% amplitude
Transition
time
10% amplitude
0%
Linearity
Peak deviation of an edge from a straight line through the 10%- and 90%amplitude points, expressed as percentage of pulse amplitude.
Figure 11. Linearity
90% amplitude
Deviation
10% amplitude
0% amplitude
100% amplitude
Jitter
Short-term instability of one edge relative to a reference edge. Usually specified
as rms value, which is one standard deviation or “sigma”. If distribution is
assumed Gaussian, six sigma represents 99.74% of the peak-peak jitter.
The reference edge for period jitter is the previous leading edge. That for delay
jitter is the leading edge of the trigger output. Width jitter is the stability of the
trailing edge with regard to the leading edge.
Stability
Long-term average instability over a specific time, for example, hour, year.
Jitter is excluded.
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Preshoot, Overshoot, Ringing
Accuracy window
Repeatability band
Settling time
90%
amplitude
Amplitude
accuracy
band
Preshoot and overshoot are peak distortions preceding/following an edge.
Ringing is the positive-peak and negative-peak distortion, excluding overshoot,
on pulse top or base. A combined preshoot, overshoot, and ringing specification
of e.g. 5% implies:
– Overshoot/undershoot < 5%
– Largest pulse-top oscillation
– < +5%, of pulse amplitude
Figure 12. Preshoot, overshoot, ringing
Overshoot
(e.g., 5%)
Ringing
(POSITIVE)
(e.g., +3%)
100%
amplitude
Ringing
(NEGATIVE)
(e.g., -2%)
0%
amplitude
Preshoot
(e.g., 2%)
Settling Time
Time taken for pulse levels to settle within level specifications, measured from
90% point on leading edge.
Figure 13. Setting time
Figure 14. Repeatability
90%
amplitude
Settling time
Amplitude
accuracy
band
Repeatability
When an instrument operates under the same environmental conditions and
with the same settings, the value of a parameter will lie within a band inside the
accuracy window. Repeatability defines the width of this band.
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08 | Keysight | Pulse Parameter Denitions - Application Note
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© Keysight Technologies, 2013 - 2014
Published in USA, August 3, 2014
5991-1943EN
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