Rohde & Schwarz SMBV100A, Operating Manual

Page: 397 / 911

Instrument Function
R&S
®
SMBV100A
382 Operating Manual 1176.8016.02 ─ 17
The Figure 5-24 depicts the stages involved in the processing and resampling of a
waveform in the ARB.
Figure 5-24: Processing of the waveform files in the ARB
The used system clock and sample rate depend on the installed otions. In this descrip-
tion, we assume an instrument equipped with the combination of R&S
SMBV-B10/
K522. This R&S SMBV uses a 200 MHz system clock and a sample rate of max 200
MSamples/s. For more information, refer to the data sheet.
Impact of the Resampling Lowpass Filter
As illustrated on the Figure 5-24 , the lowpass filter in the resampling stage is a distor-
tion-free for signals with the following maximum baseband bandwidth:
BasebandBandwidth
max
, MHz = 0.31 x f
input
.
An externally created waveform file have 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 than calculated as follow:
f
input
≥
BasebandBandwidth / 0.31
In instrument equipped with the combination R&S SMBV-B10/K522, a modulation sig-
nal with a sample rate f
input
= 200 MHz is passed directly to the digital-to-analog con-
verter (DAC), i.e. the resampling unit is bypassed. After the DAC, this signal features a
RFBandwidth
max
= 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.
In comparison with conventional ARB generators that often assume oversampling fac-
tors of 4, the ARB generator of the R&S
SMBV requires low oversampling factors, but
still providing excellent signal quality in terms of EVM and ACP.
A reduced sample rate saves significantly the amount of memory or allows an
increased signal cycle time, vice versa.
Impact on the Enabled Number of Marker Signals on the Waveform Length
The R&S SMBV provides the possibility to define marker signals, that are sent to the
marker outputs in synchronicity with the I/Q output signals. Marker signals can be
either predefined or subsequently defined (see also
Chapter 5.9.2.7, "Marker Output
Signals" , on page 336).
Baseband Signal - Baseband Block