Periodic Timer (Frame Trigger) - Agilent Technologies X Series Manual

Periodic Timer (Frame Trigger)

Pressing this key, when it is not selected, selects the internal periodic timer signal as the trigger.
Triggering occurrences are set by the Period parameter, which is modified by the Sync Source and
Offset. Pressing this key, when it is already selected, accesses the periodic timer trigger setup functions.
If you do not have a sync source selected (it is Off), then the internal timer will not be synchronized with
any external timing events.
Key Path
Example
State Saved
Readback
Status Bits/OPC dependencies
Initial S/W Revision
Periodic Timer Triggering:
This feature selects the internal periodic timer signal as the trigger. Trigger occurrences are set by the
Periodic Timer parameter, which is modified by the Sync Source and Offset.
The figure below shows the action of the periodic timer trigger. Before reviewing the figure, we'll
explain some uses for the periodic trigger.
A common application is measuring periodic burst RF signals for which a trigger signal is not easily
available. For example, we might be measuring a TDMA radio which bursts every 20 ms. Let's assume
that the 20 ms period is very consistent. Let's also assume that we do not have an external trigger source
available that is synchronized with the period, and that the signal-to-noise ratio of the signal is not high
enough to provide a clean RF burst trigger at all of the analysis frequencies. For example, we might want
to measure spurious transmissions at an offset from the carrier that is larger than the bandwidth of the RF
burst trigger. In this application, we can set the Periodic Timer to a 20.00 ms period and adjust the offset
from that timer to position our trigger just where we want it. If we find that the 20.00 ms is not exactly
right, we can adjust the period slightly to minimize the drift between the period timer and the signal to be
measured.
A second way to use this feature would be to use Sync Source temporarily, instead of Offset. In this
case, we might tune to the signal in a narrow span and use the RF Burst trigger to synchronize the
periodic timer. Then we would turn the sync source off so that it would not mis-trigger. Mis-triggering
can occur when we are tuned so far away from the RF burst trigger that it is no longer reliable.
A third example would be to synchronize to a signal that has a reference time element of much longer
period than the period of interest. In some CDMA applications, it is useful to look at signals with a short
periodicity, by synchronizing that periodicity to the "even-second clock" edge that happens every two
Trigger
TRIG:SOUR FRAM
TRIG:<meas>:SOUR FRAM Measurements other than Swept SA
Saved in instrument state
[Sync: <value of Sync Source>], for example, [Sync: External 1]
The Status Operation Register bit 5 "Waiting for Trigger" is set at the same
time as the Sweeping or Measuring bit is set. It is cleared when the trigger
actually occurs (that is, after the trigger event occurs and all the applicable
trigger criteria have been met). A corresponding pop-up message ("Waiting
for trigger") is generated if no trigger signal appears after approximately 2 sec.
This message goes away when a trigger signal appears.
Prior to A.02.00
Swept SA measurement
Trigger
591