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Keysight Technologies
Pulse Parameter Definitions
Application Note
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 defined. This document describes
and illustrates all main pulse parameter definitions. 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 specifications comparable amongst each other.
Pulse period
External
trigger signal
Trigger
delay
Trigger
output
Pulse Transition
Pulse width times
delay
Output
Double pulse
output
Double pulse delay
Delay A
Channel A
output
Interchannel
delay skew
Channel B
output
Delay B
Figure 1. Overview of the pulse parameters
Time Reference Point
The time reference point is at the median of the amplitude (50% amplitude
point on pulse edge).
100%
100%
50% Median
50% Median
0%
0%
Figure 2. Time reference at median amplitude
Pulse Period
The time interval between the leading edge medians of consecutive
output pulses.
50%
50%
Pulse period
Figure 3. Pulse period Pulse period
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
Figure 4. Trigger delay
3
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
Figure 5. Pulse 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.
Max high level
High level
Amplitude Median
Window
Low level
Offset
Trigger
output
Zero volts
Output
signal
Fixed delay Variable delay
Min low level
Figure 6. Pulse levels
4
Pulse Delay
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
Fixed delay Variable delay
Figure 7. Pulse delay
Double Pulse Delay
Interval between leading edge medians of the double pulses.
Double pulse delay
Figure 8. Double pulse delay
Interchannel Delay (Skew)
Interval between corresponding leading-edge medians of the output signals.
100%
90% amplitude
Channel A
output
Transition
Interchannel
delay skew
time
Channel B
output
10% amplitude
Figure 9. Interchannel delay 0%
5
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%
Figure 10. Transition time
Linearity
Peak deviation of an edge from a straight line through the 10%- and 90%-
amplitude points, expressed as percentage of pulse amplitude.
100% amplitude
90% amplitude
Deviation
10% amplitude
0% amplitude
Figure 11. Linearity
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.
6
Preshoot, Overshoot, Ringing
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: