Configuring the Internal Baseband Source
R&S
®
SMW200A
300User Manual 1175.6632.02 ─ 30
f
input
is retrieved from the waveform (the default sample rate tag) or is defined by the
corresponding parameter in the ARB user interface.
The Figure 5-16 depicts the stages involved in the processing and resampling of a
waveform in the ARB.
Figure 5-16: Processing of the waveform files in the ARB
f
input
= Waveform sample rate
b = Usable bandwidth factor
f
SysClk_max
= SystemClock
max
= SampleRate
max
Where:
●
f
SysClk_max
= SystemClock
max
= SampleRate
max
= 200 MHz (R&S SMW-B10/-K522)
and 2.4 GHz (R&S SMW-B9/-K527
●
b = 0.4 (R&S SMW-B10) and b = 0.4165 (R&S SMW-B9)
Impact of the Resampling Filter
As illustrated in Figure 5-16, the filter in the resampling stage is distortion-free for sig-
nals with the following maximum baseband bandwidth:
Usable_Bandwidth
max
[MHz]
=
b* f
input
.
Where b is the usable bandwidth factor and its value depends on the installed options:
●
b = 0.4 (R&S SMW-B10)
●
b = 0.4165 (R&S SMW-B9)
An externally created waveform file has to provide a sample rate f
input
that is high
enough for perfect signal reconstruction. For distortion-free resampling the lower
bound of the required sample rate f
input
is then calculated as follows:
f
input
≥
Usable_Bandwidth
/
b
Thus, a modulation signal with a sample rate f
input
= 200 MHz fed in the baseband gen-
erator ensures the Usable_Bandwidth
max
. After the DAC, this signal features a
RF_Bandwidth
max
= 2*b*f
input
=
2*b*200
MHz
=
160
MHz.
Impact of the Oversampling Factor
Waveforms generated by the R&S WinIQSIM2 software can be optimized by choosing
a suitable integer oversampling factor.
Conventional ARB generators often assume oversampling factors of 4. The ARB gen-
erator of the R&S SMW requires low oversampling factors and still provides excellent
signal quality in terms of EVM and ACP.
Using the Arbitrary Waveform Generator (ARB)
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