Rohde & Schwarz FSH4, Руководство по эксплуатации

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R&S FSH Spectrum Analyzer Mode
Performing Spectrum Measurements
Operating Manual 1309.6275.12 - 14 51
2.1.3.2 Setting the Burst Length
The burst length is the measurement time that the R&S FSH performs measurements
with. The burst length can be equal or less than the sweep time.
M Press the MEAS key.
M Press the "Burst Length" softkey.
The R&S FSH opens an input field to define the burst length.
M Enter the length of the burst you need.
The R&S FSH performs the measurement over the time you have entered.
If the measurement time you have entered was greater than the sweep time, the
R&S FSH sets a burst length equal to the sweep time. To work with a greater burst
length, you have to increase the sweep time first.
The minimum burst length is the time corresponding to one trace pixel (= sweep
time / 631).
2.1.3.3 Setting the Reference Level
The reference level is the power level that the R&S FSH expects at the RF input. When
selecting the reference level, make sure that you do not overload the R&S FSH by
applying a signal whose power exeeds the maximum reference level.
Because the resolution bandwidths of the R&S FSH are implemented digitally after the
A/D converter, the signal level at the A/D converter can be higher than the level
indicated by the trace, depending on the selected resolution bandwidth.
To prevent the A/D converter from being overloaded, the signal must be measured at
the widest resolution bandwidth and video bandwidth with the peak detector. The trace
maximum then determines the best reference level.
To simplify operation and to prevent incorrect measurements, the R&S FSH has an
automatic routine for setting the reference level.
M Press the AMPT key.
M Press the "Level Adjust" softkey.
The R&S FSH performs a measurement to determine the ideal reference level.
It uses a resolution bandwidth of 3 MHz, a video bandwidth of 3 MHz and the peak
detector. After finishing the automatic measurement, the R&S FSH sets the ideal
reference level.
2.1.3.4 Using a Trigger
Usually you will apply a trigger when measuring bursts.
If a trigger is active, the R&S FSH uses the video trigger for TDMA measurements by
default. The video trigger level is at 50 % of the range of the vertical axis but is
variable. This means, the R&S FSH triggers a measurement if the rising edge of the
burst exceeds this 50 % line.