Signal Routing and System Configuration
R&S
®
SMW200A
122User Manual 1175.6632.02 ─ 30
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
2) perform 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 SMW 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 SMW to receive these values, enable the param-
eter "DIG IQ Auto Setting" on page 164.
In the second automatic way, the R&S SMW 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 4-6.
Figure 4-6: Resampling principle of external digital baseband signals
* = Max. sample rate depends on connected device
f
input
= Max. sample rate
The max. sample rate depends on the installed options:
– The R&S SMW can process digital signals with sample rate f
input
= 400 Hz to
200 MHz.
– The Wideband baseband version working in standard mode uses, can process
wideband digital signals with f
input
≤ 2.4 GHz.
The internal signal processing in the Standard baseband is based on a sample
rate with a maximum value (f
sample, max
= 200 MHz or 100 MHz) that depends on
the capabilities of the connected transmitting/receiving device.
●
Maximum modulation bandwidth
A baseband signal with a sample rate f
smaple
< f
smaple, max
(i.e. smaller than the used
system clock) is interpolated, see Figure 4-6. The resulting modulation bandwidth
is calculated as sample rate * 0.8.
With a sample rate f
sample, max
of exactly 200 MHz, the modulation bandwidth in the
Standard baseband is 160 MHz.
Overview of the Input and Output Signals and Interfaces
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