Instrument Function
R&S
®
SMBV100A
250Operating Manual 1176.8016.02 ─ 17
See also Chapter 5.5.13.1, "Overview of LF Generator", on page 261.
External Modulation Sources
The modulation input EXT MOD at the instrument front provides the external modula-
tion sources for amplitude, frequency and phase modulation.
The external modulation signal for AM, FM and PM 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 V, otherwise modulation distortions might
occur.
The PULSE EXT connector at the rear of the instrument controls the external pulse
modulation. The input shows some hysteresis with threshold levels of 0.5 V/1.5 V. The
voltage must not exceed 5 V.
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 I/Q
Amplitude modulation (AM) / + + (+)* -
Frequency modulation (FM) + / - + +
Phase modulation (PhiM) + - / + +
Pulse modulation (+)* + + / +
Vector modulation (I/Q) - + + + /
* (+) = compatible with reduced AM modulation performance
5.5.12.2 Amplitude Modulation (AM)
An internal or external source can be selected for amplitude modulation. The LF GEN
modulation generator is available as the internal source. The I/Q modulator is used for
amplitude modulation. Two-tone AM is possible by simultaneously switching on the
external and internal source.
The MOD EXT and PULSE EXT input connectors for external feed of analog modula-
tion signals are at the rear of the instrument. The coupling mode of the input (AC or
DC) can be selected.
It is not possible to use AM simultaneously with:
●
I/Q modulation,
●
arbitrary waveform generation,
●
digital modulation and
●
digital standards.
The AM modulation depth is limited by the maximum peak envelope power (PEP).
RF Block
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