Keysight E6640A, Measurement Applications User & Programmer Reference

Page: 1281 / 2870

10 Spectrum Emission Mask Measurement
Sweep/Control
Backwards Compatibility
Notes The legacy :TRIGger[:SEQuence]:SLOPe command affects the slopes for the VID, LINE, EXT1, EXT2,
and RFB triggers.
Initial S/W Revision Prior to A.02.00
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
Trigger
Example TRIG:SOUR FRAM Swept SA measurement
TRIG:<meas>:SOUR FRAM Measurements other than Swept SA
State Saved Saved in instrument state
Readback [Sync: <value of Sync Source>], for example, [Sync: External 1]
Status Bits/OPC
dependencies
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.
Initial S/W Revision Prior to A.02.00
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.
W-CDMA & HSPA Measurement Applications Reference 1281