Rohde & Schwarz SMM100A, Руководство пользователя

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Multi-instrument setups
R&S
®
SMM100A
453 User Manual 1179.1341.02 ─ 05
Fulfilling the prerequisites for a correct signal processing of the externally sup-
plied digital baseband signal
The Chapter 9.3.4.4, "Important signal parameters and interface's characteristics" ,
on page 451 emphasis why and which signal parameters are important for the correct
internal signal processing of externally supplied signals in the R&S
SMM100A. 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
– Estimated automatically by the internal measurement function
Use the function
Auto Level Set to trigger the R&S SMM100A to measure the
input signal, estimate the peak level and RMS level and calculate the crest fac-
tor out of them.
Tip: For a correct signal leveling:
1) Enable an appropriate measurement time.
2) Execute one measurement for each baseband source.
3) Set the measurement period to a time value that is long enough to capture
several periods of the input signal.
– Determined automatically
The R&S
SMM100A can receive the values from the connected transmitter.
If the external digital signal source is a second Rohde & Schwarz instrument, it
signals the peak level and the RMS level of the signal over the digital input
interface. To enable the R&S
SMM100A to receive these values, enable the
parameter "DIG IQ Auto Setting" on page 475.
In the second automatic way, the R&S SMM100A adjusts the corresponding input
fields with the measured/received values. The internal gain control mechanism
uses these received values to adjust the input signal gain to achieve an optimal
dynamic range.
●
Sample rate
External input signals with sample rates different than the system clock are resam-
pled, as illustrated on
Figure 9-3 .
Figure 9-3: Resampling principle of external digital baseband signals
* = Max. sample rate depends on connected device
f
input
= Max. sample rate
●
Maximum modulation bandwidth
Control and operation of external instruments