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The Spectrum Application
R&S
®
FPC
80
User Manual 1178.4130.02 ─ 07
Selecting the AM modulation depth measurement
1. Press the "Meas" key to open the measurement menu.
2. Select the "Measurement Mode" menu item to select the measurement.
3. Select the "AM Modulation Depth" menu item.
The R&S
FPC measures the modulation depth by placing three markers on the
trace.
The first marker is placed on the peak level - the R&S
FPC assumes that the high-
est level is the carrier. The second and third markers are delta markers. These
markers are placed symmetrically on the adjacent peak values to the left and right
of the carrier.
From the values of the markers, the R&S
FPC then calculates the AM modulation
depth. The AM modulation depth is the ratio between the power values at the refer-
ence marker and at the delta markers. When the powers of the two AM side bands
are not the same, the R&S
FPC uses the mean value of the two sideband values.
If the R&S
FPC is unable to find any AM modulated carriers, it shows a message
that the measurement is not possible.
Moving the markers
You can move the markers manually and individually to other positions, if necessary.
1. Press the "Meas" key to open the measurement menu.
2. Select one of the "Marker <x>" menu items to select the corresponding marker.
3. Move the marker to a new position.
Defining a threshold
1. Press the "Meas" key to open the measurement menu.
2. Select the "Threshold" menu item.
The R&S
FPC opens an input field to define a threshold.
3. Enter the threshold value you need.
The threshold is represented as a horizontal blue line in the diagram area. Signals
below that threshold are not interpreted as sideband signals.
Optimizing the measurement settings
In order to get the best results, you can use the automatic adjustment routine that the
R&S
FPC offers.
1. Press the "Meas" key to open the measurement menu.
2. Select the "Adjust Settings" menu item.
The R&S
FPC performs a measurement to determine the ideal reference level, fre-
quency and span to display all harmonics.
Measurements and Result Displays