Configuring the Internal Baseband Source
R&S
®
SMW200A
249User Manual 1175.6632.02 ─ 16
Predefined baseband filters
Refer to Chapter 4.6.5.3, "Predefined Baseband Filters", on page 297 for an overview
of the available baseband filters.
User filter
The user filter file must have extension *.vaf and can be created with the
Rohde & Schwarz software tool filter wizard.
The filter wizard (filtwiz) is a tool from Rohde & Schwarz designed for creating filter
files that can be imported on a R&S SMW. Its main purpose is the conversion of user-
defined finite impulse response (FIR) filters into the filter format (*.vaf). Beyond this
filtwiz provides designs for standard filters, e.g. root raised cosine (RRC), Gaussian.
The program was developed on a 32-bit Microsoft Windows platform under MATLAB.
For more information, refer to the description "Introduction to "filtwiz" Filter Editor" at
the Rohde & Schwarz webpage.
The remote commands required to define the filter settings are described in Chap-
ter 13.18.4.2, "SOURce:BB:DM Subsystem", on page 890 and the corresponding sec-
tion in the user manual of each firmware option.
Related settings:
●
Chapter 4.6.3.5, "Filter Settings", on page 276
●
Filter settings in the dialogs of the firmware options
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.
Common Functions and Settings in the Baseband Domain
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