R&S FSMR, Operating Manual

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R&S FSMR Analyzer - MEAS
1166.3363.12 4.16-39 E-2
Measurement of the AM Modulation Depth
The MODULATION DEPTH softkey switches on the measurement of the AM
modulation depth. An AM-modulated carrier is required on the screen for
ensuring correct operation.
The level value of
MARKER 1 is taken as the carrier level. When this
function is activated, MARKER 2 and MARKER 3 are automatically set
symmetrically to the carrier on the adjacent peak values of the trace as delta
markers and
MARKER 2 is activated for the entry.
When the position of MARKER 2 (delta) is changed, MARKER 3 (delta) is
moved symmetrically with respect to the reference marker ( MARKER 1 ).
If the data entry is activated for MARKER 3 ( MARKER 1 2 3 4 softkey), the
latter can be moved for fine adjustment irrespective of MARKER 2 .
The R&S FSMR calculates the power at the marker positions from the
measured levels. The AM modulation depth is calculated from the ratio
between the power values at the reference marker and at the delta markers.
When the powers of the two AM side bands are unequal, the mean value of
the two power values is used for AM modulation depth calculation.
Measurement example :
The AM modulation depth of a carrier modulated with 1 kHz is to be
measured at 100 MHz.
[ PRESET ] The R&S FSMR is set to the default setting.
[ CENTER : 100 MHz ] The center frequency is set to 100 MHz.
[ SPAN : 5 kHz ] The span is set to 5 kHz.
[ AMPT : 0 dBm ] The reference level is set to 0 dBm.
[ MKR FCTN ] MARKER 1 is switched on and positioned at the
maximum of the displayed trace.
[ MODULATION The measurement of the AM modulation depth is
DEPTH : 1 kHz ] switched on. MARKERS 2 and 3 (delta markers) are
set to the adjacent peak values of the trace and are
activated for the frequency entry.
The AM modulation depth is output in % in the
marker info field.
When 1 kHz is entered, MARKER 2 can be exactly
positioned on 1 kHz and MARKER 3 at -1 kHz from
the reference marker.
IEC/IEEE-bus command:
CALC:MARK:FUNC:MDEP ON;
CALC:MARK:FUNC:MDEP:RES?