Source User’s Guide 39
Basic Digital Operation
Triggering a Waveform
Triggering a Waveform
Triggers control data transmission by controlling when the transceiver
transmits the modulating signal. You can configure trigger settings so that
data transmission occurs once (Single mode), or continuously (Continuous
mode).
A trigger signal contains both positive and negative states; you can use either
for triggering.
When you initially select a trigger mode or when you change from one
triggering mode to another, you may lose the carrier signal at the RF output
until the modulating signal is triggered. This is because the source sets the I
and Q signals to zero volts prior to the first trigger event. To maintain the
carrier signal at the RF output, create a data pattern with the initial I and Q
voltages set to values other than zero.
When you initially turn the Arb State ON or select a trigger mode or when you
change from one triggering mode to another, you may temporarily lose the
carrier signal for a few tens of milliseconds at the RF output. The Arb will
present the idle IQrms value of the next Arb waveform to the IQ modulator. This
ensures that the RF carrier output is at the correct amplitude level while the
Arb waits for a trigger. When that trigger is received, the Arb begins playing
the waveform and the modulated RF carrier exhibits no undesirable transients.
There are two parts to configuring a waveform trigger:
— Type determines the behavior of the waveform when it plays (see “Trigger
Type” on page 39).
— Source determines how the source receives the trigger that starts the
modulating waveform playing (see “Trigger Source” on page 40).
Trigger Type
Type defines the trigger mode: how the waveform plays when triggered.
Trigger Type is selected by clicking the Input/Output key, followed by the
Modulation Setup, ARB Setup, Basic Control, Trig Type keys.
— Continuous mode repeats the waveform until you turn the signal off or
select a different waveform, trigger mode, or response
—Free Run immediately triggers and plays the waveform; triggers
received while the waveform is playing are ignored.
—Trigger and Run plays the waveform when a trigger is received;
subsequent triggers are ignored.
— Single mode plays the waveform once.
—No Retrigger ignores triggers received while a waveform is playing. If a
trigger is received early it will be ignored. The gap in your playback is
dependent on the trigger period, after which time the RF will start up
again where it is expected.
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