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Instrument Function
R&S
®
SMC100A
147
Operating Manual 1411.4060.32 ─ 04
5.4.1.2
Modulation Sources
The following modulations use internal and external modulation sources:
●
Amplitude modulation
●
Pulse modulation
●
Frequency modulation
●
Phase modulation
Internal Modulation Sources
An LF generator and a pulse generator are available as internal modulation sources. The
LF generator supplies sinusoidal. The pulse generator provides single and double pulse
modulation with selectable pulse widths and periods.
See also
chapter 5.5.1, "LF Generator Overview"
External Modulation Sources
The modulation inputs MOD EXT and PULSE EXT at the rear of the instrument are pro-
vided as the external modulation source for amplitude, pulse, frequency and phase mod-
ulation.
The external modulation signal at the input must have a voltage of U
S
= 1 V (U
EFF
= 0.707
V) in order to achieve the displayed modulation depth and range. The input voltage should
not exceed 1.1 Vs, otherwise modulation distortions might occur. With external pulse
modulation, the switching point is max. 2.4 V and the voltage at the input should not
exceed 5 V. The maximum modulation frequency is 10 MHz for frequency and phase
modulation.
Simultaneous Operation of Several Modulations or Other Operating Modes
The table shows the modulations and operating modes which can be activated simulta-
neously (+) or which deactivate each other (-).
AM
FM
PhiM
Pulse
Amplitude modulation (AM)
/
+
+
-
Frequency modulation (FM)
+
/
-
+
Phase modulation (PhiM)
+
-
/
+
Pulse modulation (Pulse)
-
+
+
/
5.4.2 Amplitude Modulation (AM)
An internal and/or external source can be selected for amplitude modulation. The LF
modulation generator is available as the internal source.
The MOD EXT input connector for external feed of analog modulation signals is at the
front of the instrument. The coupling mode of the input (AC or DC) can be selected.
The AM modulation depth is limited by the maximum peak envelope power (PEP).
Modulations