Rohde & Schwarz SMW200A - About the Baseband Offsets

Configuring the Internal Baseband Source
R&S
®
SMW200A
383User Manual 1175.6632.02 ─ 16
4.12.1 About the Baseband Offsets
The applied baseband frequency and phase offset and path gain affect the signal on
the output of the corresponding block, "Baseband" or "BB Input". The shifting of the
central frequency of the baseband signal is one of the tasks of the resampler.
4.12.1.1 Impact of the Frequency Offset
For some applications, it is helpful to shift the baseband signal with a user defined
baseband frequency offset to a different center frequency so that the signal character-
istics are improved. The provided parameter frequency offset shifts the center fre-
quency of the wanted baseband signal and provides a quick way to shift the used fre-
quency band in the RF frequency domain without modifying the RF settings.
See Chapter 4.12.3, "How to Improve Signal Characteristics by Shifting the Wanted
Baseband Signal", on page 387.
Limitations
The complex I/Q bandwidth of the shifted useful signal must not exceed the total avail-
able baseband bandwidth (see data sheet). The setting range of the frequency offset is
then calculated as follows:
-(TotalBasebandBandwidth/2) + f
use
/2
≤ f
offset
≤ (TotalBasebandBandwidth/2) - f
use
/2 ,
where
f
use
is the complex useful bandwidth of the I/Q signal before the offset
f
offset
is the frequency offset
The Figure 4-23 illustrates the setting range of the frequency offset.
Figure 4-23: Setting range of frequency offset
Shifting and Boosting the Baseband Signal