Instrument Function
R&S
®
SMU200A
244Operating Manual 1007.9845.32 ─ 15
Note: Coupling for external feed via input EXT MOD can be set independently for mod-
ulations AM, FM and PHIM.
"AC"
The d.c. voltage content is separated from the modulation signal.
"DC"
The modulation signal is not altered.
SCPI command:
[:SOURce<hw>]:PM:EXTernal:COUPling on page 762
External Input Impendance
Selects the impedance for external feed via the EXT MOD input.
Selection 50 Ohm and high (>100 kOhm) is available.
Note: This setting affects all analog modulations which use the external modulation
source.
SCPI command:
[:SOURce<hw>]:INPut:MODext:IMPedance on page 721
5.5.11.6 Pulse Modulation (PM)
Pulse modulation is available for the basic unit (R&S SMU + frequency option R&S SMU-
B10x) without additional equipment options.
An additional frequency option (R&S SMU-B20x) is required for a two-path instrument.
An internal or external source can be selected for pulse modulation. A simple rectangular
signal with selectable repetition frequency is available as the internal signal. This signal
is formed from the sinusoidal signal supplied by the LF generator.
The external signal is input via the EXT MOD connector at the rear of the instrument. The
polarity of the external pulse modulation can be selected. If Polarity is set to Normal, the
RF level is ON if the level is HIGH at the modulation input.
Automatic Level Control is deactivated with pulse modulation!
When pulse modulation is activated, the ALC state of the R&S SMU is automatically
changed to "ALC OFF" ("Sample & Hold"). In this state, the ALC loop is opened and the
output level is not regulated but the level modulator is set directly. In order to set the
correct output level, a sample & hold measurement is executed after each frequency or
level setting.
The level is decreased by 30 dB during "Sample&Hold" measurement.
Pulse Modulation Menu
To open the "Pulse Modulation" menu, select "RF/A Mod > Configure > Pulse Modula-
tion" or use the MENU key under "RF/A Mod".
RF Signal and Analog Modulations - RF Block
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