Signal Routing and System Configuration
R&S
®
SMW200A
135User Manual 1175.6632.02 ─ 16
Why the instrument monitors the signal internally and how to avoid overflow
The R&S SMW constantly monitors the input and output digital signal and indicates an
overflow status.
●
Overflow of the input signal (Crest Factor and Peak Level) is indicated if the
entered "Peak Level" (in dB full scale) value does not correspond to the real value
Tip: The overflow status is indicated as long as the signal level is not reduced and
the peak level value corrected. Trigger "Auto Level Set" to collect the required val-
ues and adjusts the settings automatically.
●
Overflow of the output signal is indicated if the digital signal is clipped, i.e. if the
level of the output signal, or the noise level (AWGN) are too high.
3.3.4.1 Specific Characteristics of the Digital I/Q Interface
What is a "digital channel" and how are the channels distributed to the base-
bands
The external digital signals supplied at the DIG I/Q interfaces of the instrument may
contain more than one, possibly even multiplexed, digital channels. The R&S SMW
processes each of these digital channels as a separate signal. Over the settings provi-
ded at the user interface, you can route the available digital channels of each of the
digital interface to one of the baseband blocks.
Do not mistake the term channel used here with the terms Fading channel or signal
path.
For a description of the required settings, see Source.
Fulfilling the prerequisites for a correct signal processing of the externally sup-
plied digital baseband signal
The Chapter 3.3.4, "Important Signal Parameters and Interface's Characteristics",
on page 133 emphasis why and which signal parameters are important for the correct
internal signal processing of externally supplied signals in the R&S SMW. This section
focuses on the way these requirements are fulfilled and explains how the instrument
deals with signals deviating from the expected values:
●
Crest factor, peak level and RMS level
These values can be adjusted in one of the following ways:
– Adjusted manually
If you have knowledge about these values, it is best to enter them directly (see
"Crest Factor" on page 176)
– Estimated automatically by the internal measurement function
Use the function Auto Level Set to trigger the R&S SMW to measure the input
signal, estimate the peak level and RMS level and calculate the crest factor out
of them.
Tip: For a correct signal leveling:
1) enable an appropriate measurement time
Overview of the Input and Output Signals and Interfaces
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