Instrument Function
R&S
®
SMU200A
234Operating Manual 1007.9845.32 ─ 15
See also chapter 5.5.12.1, "LF Generator Overview", on page 246.
External Modulation Sources
The EXT MOD input at the rear of the instrument is provided as the external modulation
source for amplitude, pulse, frequency and phase modulation. The external signal for
broadband amplitude modulation is fed in via the I-input.
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 BB-AM I/Q DM ARB
Amplitude modulation (AM) / + + + - - - -
Frequency modulation (FM) + / - + + + + +
Phase modulation (PhiM) + - / + + + + +
Pulse modulation + + + / + + + +
Broadband AM (BB-AM) - + + + / - - -
Vector modulation (I/Q) - + + + - / - -
Digital modulation (DM) - + + + - - / -
ARB - + + + - - - /
5.5.11.2 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 EXT MOD input connector for external feed of analog modulation signals is 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:
●
broadband AM,
●
I/Q modulation,
●
arbitrary waveform generation,
●
digital modulation and
●
digital standards.
RF Signal and Analog Modulations - RF Block
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