60
Instrument Functions
width set) in order to obtain a correct display. Pushing the
key SWEEP will open the selection menu. The sweep time
can be varied within the specified limits. The setting of the
parameters is performed as described in chapter 5. In or-
der to assist the user when setting the sweep time, an au-
tomatic selection of the sweep time with respect to the
RBW and the span settings may be chosen with the soft-
key Auto. The automatic mode will always set the sweep
time to the shortest possible value consistent with the cor-
rect display of the spectrum content.
The R&S®HMS-X spectrum analyzer will sweep the selec-
ted frequency range continuously (softkey CONTINUOUS),
i.e., after a sweep was completed, a new one will be star-
ted and the display refreshed. If continuous sweeping is
not desired (e.g., if a single event shall be recorded upon
a trigger), there is also the possibility of selecting SINGLE
sweep. If single sweep is selected, the spectrum analy-
zer will sweep the frequency range once or it displays the
video signal vs. time if the span is set to zero. The instru-
ment will only repeat the measurement after the softkey
Single was pushed again. Additionally the soft menu TRIG-
GER offers diverse trigger functions in order to react to
events.
6.6.1 Source
With the softkey SOURCE an internal / external trigger
source or the video trigger (VIDEO) can be selected. If the
internal source is selected (int.), the spectrum analyzer is
in the continuous sweep mode, i.e. when one sweep of
the span has been completed, the sweep is automatically
repeated from the start of the span. If the external source
is selected (ext), the sweep is started by an external trigger
signal. The video trigger (VIDEO) allows to trigger on a de-
fined signal level. A sweep starts when the video voltage
exceeds a settable value. When a frequency spectrum is
being displayed (for example span 100 kHz), there is no gu-
arantee that a signal to generate a video voltage is pre-
sent at the start frequency. Under these circumstances the
The video trigger can be only activated in zero span (span = 0 Hz).
spectrum analyzer would never perform a sweep. With a
span setting of 0 Hz (zero span) the spectrum analyzer chan-
ges the display from spectrum versus time to discrete vol-
tage versus time. The X-axis of the measurement diagram
represents the time axis, starting with time 0s and ends
with the selected sweep time. The minimum sweep time in
zero span mode is 2 ms, the maximum is 1000 s.
This so-called edge trigger works reliably up to a delta of
at least 3 dB between the selected level (trigger line) and
the maximum applied signal amplitude. The level of the vi-
deo trigger (y-axis) can be set with the softkey LEVEL.
6.6.2 Slope
With the softkey SLOPE the sweep will be started by a
positive or negative edge of an external trigger signal. The
external trigger signal is applied via the BNC connector
EXTERNAL TRIGGER (TTL logic levels).
6.7 Trace settings (TRACE)
The trace menu can be opened by pressing the TRACE
key. The R&S®HMS-X can simultaneously display up to 3
waveforms on the screen. The trace mode of trace 2 and 3
is fixed and can not be changed by the user:
❙
Trace 1
= normal Sweep (yellow / free configurable)
❙
Trace 2
= Max hold trace (purple)
❙
Trace 3
= Min hold trace (green)
Trace 2 and 3 are each based on the freely configurable
trace 1. Trace 2 and 3 can only be turned on (ON) or off
(OFF). If all traces are enabled, it is possible to analyze the
signal „progression“ by the resulting min-max graph (ple-
ase refer to figure 6.5).
There are several modes of curve display (TRACE MODE):
❙
CLEAR / WRITE
(default setting): clears the old trace
during a new sweep
Fig. 6.3: Signal with AM modulation 50% in zero span with linear scaling
The sweep can only be started by an external trigger signal. A
trigger delay can be not defined.
Fig. 6.4: Signal with AM modulation 50% in zero span with logarithmic
scaling
Summary of Contents for HMS-X
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