54
Brief Description
ted level of –10 dBm in the upper screen area. The first har-
monic of the sine wave should now appear at 200 MHz. De-
pending on the purity of the signal this harmonic may be
well or hardly visible with the presently active settings.
In order to measure the distance of the first harmo
-
nic to the fundamental proceed as follows:
Press the soft key MARKER and move the knob by one
detent position to the right in order to select a second
marker (M2). Activate the marker by pressing the soft key
DISPLAY. The second marker will now appear in the center
of the display. Select the marker by pressing the soft key
DISPLAY (the marker indication will turn to orange) and
move it with the knob (to the right) or via the keyboard by
directly entering the value 200 MHz.
4.3.1 Selection of the proper filter settings
In order to better resolve the harmonic from the noise, the
RBW and the VBW filters should be adapted to the mea-
surement task by using the bandwidth menu (key BANDW
9
). The R&S®HMS-X standard procedure is to automati-
cally set the RBW and VBW filters such that a first appro-
ximation of a measurement of the input signal will be pos-
sible. Manual selection of the filters will be always supe-
rior to an automatic presetting. Activate the key BANDW
9
to enter the filter menu of the spectrum analyzer. Due
to the presettings, the RBW and the VBW will be set to
Auto. Activate manual setting by pressing the top soft key,
then use the knob to select the 100 kHz filter from the list
in the menu which will appear. The noise band displayed
formerly should now be markedly reduced such that the
first harmonic will be better visible. A further reduction of
the RBW would display the harmonic still better at the ex-
pense of a massively extended sweep time. Here, a com-
promise must be found between display quality and mea-
surement time, optimum for the actual measurement task.
Another means of spectrum analysis is the socalled video
bandwidth (VBW). This is nothing else but a low pass fil-
ter which filters high frequency components from the sig-
nal. Using this filter can also cause a massive increase of
the sweep time, and again a sound compromise has to be
Fig. 4.4: Measurement of the harmonic of a sine wave signal
found between display quality and measurement time. Ac-
tivate the manual VBW selection by pressing the associa-
ted soft key and use the knob to select a 10 kHz filter from
the list in the menu which will appear. Both levels (funda-
mental and harmonic) should now be well visible on the
R&S®HMS display.
4.3.2 How to measure the harmonic
In chapter 4.3.1 already two markers were positioned on
the fundamental and the harmonic, the second one on
the harmonic. Open the marker menu by pressing the
key MARKER
15
. The marker [2] is still selected (shown
as an entry on the top soft key) Change the active mar-
ker [2] from an ”absolute” marker to a “relative” delta mar-
ker by pressing the soft key DELTA. The marker display will
change from an absolute frequency and level display to a
relative frequency and level display; the values shown refer
always to the main marker (marker [1]).
4.3.3 Extended marker functions (PEAK SEARCH)
Press the key PEAK SEARCH in order to reach the exten-
ded marker functions. Select the marker to be used with
the key (MARKER >
14
). In the top screen area (where the
level and frequency values of the markers can be read) the
lettering of the marker selected will be shown pronounced
Fig. 4.5: Selection of the proper filter settings
Fig. 4.6: Measuremen of the harmonic using the delta marker
Summary of Contents for HMS-X
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