Trigger Concepts - R&S FSV-K8 Operating Manual

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R&S FSV-K8
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The trace functions affect complete measurement curves: A resulting curve is cal-
culated from several subsequent sweeps. The method of calculation (Average,
Maxhold, Minhold) can be selected here as well.
Thus the detector is the arithmetic rule for how sample data collected with a high data
rate are combined to a measurement point of one individual measurement curve,
whereas the trace mode is the rule of how samples taken from several measurement
curves are to be combined to a new resulting curve.
For the ACP measurement, the "Average" detector is set.

2.9 Trigger Concepts

As the DUT (Device Under Test) uses frequency hopping, a trigger method is neces-
sary for two reasons:
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A measurement is only possible during the period of time, when there is a TX sig-
nal (burst) at the frequency under request.
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In order to determine the modulation characteristics correctly, a synchronization
with the preamble of the signal must be supplied.
If the "Find Sync" softkey is activated, the synchronization is supplied towards the 64
bit sync word. For this purpose, in a first step a burst is searched automatically within
the RF signal, or, if selected, the external trigger or the IF power trigger are used to
determine the burst position.
In a second step the sync word position is searched by correlation of the signal with
the sync word defined in the initialization phase. The correlation is performed directly
with the FM signal, not with the data bits, which are only available after the phase
shifter has been processed. The find burst process is continued as long as no sync
word is found.
After the position of the sync word has been determined, the position of the p0 bit is
calculated from the average value of all zero trespassing points, as defined in the RF
test specification. Finally the samples are moved in a way that each sample matches
one zero trespassing point (phase shifting).
The only measurement possible without synchronization is the Output Power measure-
ment. The specified measurement time is 20% to 80% of the burst length. Without syn-
chronization the burst length is defined via the –3dB points of the power curve. With
synchronization the burst starts with the p0 bit. Therefore varying measurement results
is possible if the power of the EUT is not constant within the burst.
In order to supply stable synchronization the EUT must be operated in reduced hop-
ping mode. The EUT is only allowed to toggle between two frequencies, because oth-
erwise the repetition time for the same frequency would become higher than the record
length. If the test environment supplies an external trigger that marks the channel to be
measured a synchronization is also possible with normal hopping operation.
Operating Manual 1176.7610.02 ─ 02
Introduction to Bluetooth Measurements (K8)

Trigger Concepts

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