Configuring the Internal Baseband Source
R&S
®
SMW200A
248User Manual 1175.6632.02 ─ 30
Impact of the Filter Parameters
The following is a simple description of the filter parameters and the way they affect the
main filter characteristics. Changing filter parameters is an effective way to ensure that
the entire bandwidth of the desired signal is allowed to pass and adjust the filter form to
reach the spectrum mask requirements.
Cut Off Frequency
The cut-off frequency or corner frequency is a filter characteristic that defines the fre-
quency at the 3 dB down point. This frequency is bound to the transition band; here the
filter characteristic changes form the passband to the stopband, where the signal is
suppressed.
Rolloff Factor
The rolloff factor is a measure for the excess bandwidth compared to the ideal band-
width of a "brick like" filter. The roll off factor affects the steepness of the filter flanks. A
"Rolloff Factor" = 0 would result in the steepest theoretically possible flanks ; values
near to 1 make the flanks more flat.
Passband
The passband describes the frequency span that the filter passes unchanged. The
total passband of a filter is given as follows:
Bandwidth = (1 + "Roll Off Factor") * "Symbol Rate"
Cut Off Frequency Shift
The "Cut Off Frequency Shift" affects the cut-off frequency in the way that the filter
flanks are "moved" and the passband increases by "Cut Off Frequency Shift"*"Sample
Rate":
Cut Off Frequency = (1 + "Cut Off Frequency Shift") * "Sample
Rate"
Common Functions and Settings in the Baseband Domain
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