Rohde & Schwarz SMC100A - Pulse Modulation (PM)

Instrument Function
R&S
®
SMC100A
177Operating Manual 1411.4060.32 ─ 09
Note: The input voltage must not exceed 1.1 V
p
otherwise modulation distortions
occur.
Remote command:
[:SOURce<hw>]:PM:SENSitivity? on page 311
PhiM Ext Coupling
Selects the coupling mode ("AC" or "DC") for the external modulation signal.
Note: Coupling for external feed via input MOD EXT can be set independently for all
modulations using the external modulation signal.
"AC"
Disconnects the DC voltage component and uses only the AC com-
ponent of the modulation signal.
"DC"
Uses the modulation signal with both components, AC and DC.
Remote command:
[:SOURce<hw>]:PM:EXTernal:COUPling on page 310
Ext. Impedance
(Source "External" only)
Sets the impedance for the external modulation signal, applied at the MOD EXT con-
nector.
You can select 600 Ohm or high (>100 kOhm).
This setting affects all analog modulations which use the external modulation signal.
Remote command:
[:SOURce<hw>]:INPut:MODext:IMPedance on page 298
5.4.5 Pulse Modulation (PM)
As modulation signal, you can either use the signal of the internal pulse generator or
an externally supplied signal. In case of external source, the external signal is input via
the PULSE EXT connector at the rear of the instrument. In case of internal source, this
connector can be used as external trigger or gate signal input for internal pulse modu-
lation. The polarity and input impedance of the connector can be selected.
The pulse signal is output at the PULSE VIDEO connector at the rear of the instru-
ment.
Automatic Level Control is deactivated with pulse modulation!
When pulse modulation is activated, the R&S SMC deactivates ALC automatically
("ALC OFF", i.e. switches to "Sample & Hold" state).
The "Sample&Hold" state opens the ALC loop, and disables the automatic control of
the output level. The level modulator is set directly.
However, to correct the output level, the R&S SMC executes a "Sample & Hold" mea-
surement after each change of frequency or level settings.
The level is decreased by 30 dB during "Sample & Hold" measurement.
Modulation