The Spectrum Application (RF Measurements)
R&S
®
FPL1000
245
User Manual 1178.3370.02 ─ 03
1. Select PRESET to reset the instrument.
2. Set the center frequency to
128
MHz
.
3. Set the frequency span to
50
kHz
.
4. Select MEAS > "AM Modulation Depth" to activate the modulation depth measure-
ment.
The R&S
FPL1000 automatically sets a marker to the carrier signal in the center of
the diagram and one delta marker each to the upper and lower AM sidebands. The
R&S
FPL1000 calculates the AM modulation depth from the level differences of the
delta markers to the main marker and outputs the numeric value in the marker
information.
Figure 7-10: Measurement of the AM modulation depth
The modulation depth is displayed as "MDepth" . The frequency of the AF signal can
be obtained from the frequency display of the delta marker.
Measuring AM-Modulated Signals
The R&S
FPL1000 rectifies the RF input signal (that is, removes the negative parts)
and displays it as a magnitude spectrum. The rectification also demodulates AM-modu-
lated signals. The AF voltage can be displayed in zero span if the modulation side-
bands fall within the resolution bandwidth.
Displaying the AF of an AM-modulated signal (Zero Span)
Figure 7-11: Test setup
Measurements and Results
