80 Chapter3
Making EDGE (with GSM) Measurements
Making the Output RF Spectrum Measurement
Therefore, the trigger must be synchronous with respect to a rising
edge of a burst. The RF Burst trigger will do this if the offset is
within about 7 MHz of the carrier. Remember that since the RF
Burst trigger is wideband, the carrier will still cause the signal to
trigger. Assuming the trigger threshold remains constant, the
trigger with respect to the burst will remain constant. Since the
Frame Trigger uses an internal frame timer (clock), its period is set
so that it occurs synchronously with respect to the transmitting
frame. If an external trigger is used, it is important that it is
synchronous with the burst.
Because of these requirements, only the trigger source can be
selected while the measurement selects the burst sync type based on
the trigger source.
NOTE Video trigger source is not allowed, because when the instrument is
tuned to offset frequencies away from the carrier, the video trigger
threshold will not be reached (due to the low power level of the offset.)
Trigger Source Measurement Defined
Burst Sync
Free Run None
RF Burst RF Amplitude
Ext Front External
Ext Rear External
Frame Training Sequence
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