R&S FSW Series, Руководство пользователя

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Common Measurement Settings
R&S
®
FSW
463 User Manual 1173.9411.02 ─ 43
For general purpose measurements, an "Auto" mode is available, which provides a
compromise between a large dynamic range and a fast sweep . In this case, a
medium-sized subspan is used.
FFT mode and external mixers (R&S FSW-B21)
The subspan optimation modes "Dynamic" and "Auto" include automatic suppression
of unwanted mixing products. Thus, when using external mixers (R&S
FSW-B21), use
the "Speed" mode to obtain similar results in FFT mode as in normal sweep mode.
FFT mode and EMI measurements (R&S FSW-K54)
For EMI measurements (using R&S FSW-K54), the subspan optimation mode
"Dynamic" is not supported. "Auto" mode always uses "Speed" optimization.
Optimization for zero span sweeps
For normal sweeps in the time domain (zero span), the optimization mode determines
the selection of the A/D converter prefilter, which depends on the RBW.
In "Dynamic" mode , the narrowest possible prefilter is used.
In "Speed" mode , the widest possible prefilter is used.
In "Auto" mode , a medium-sized prefilter is used.
Number of subspans
Several analysis steps are required to cover the entire span, in particular if the span
exceeds the maximum I/Q bandwidth for a single measurement. In this case, each FFT
analysis covers a subspan. The subspan cannot be defined directly, but it can be opti-
mized according to measurement requirements, as described above. The number of
required subspans is now indicated in the sweep settings dialog box. Thus, you can
determine the required measurement time for an individual span (and thus sweep
point) as:
<Meas time p.span> = <sweep time> / <no. of subspans>
8.5.1.6 Which Data May Pass: Filter Types
While the filter is irrelevant when measuring individual narrowband signals (as long as
the signal remains within the RBW), the measurement result for broadband signals is
very dependant on the selected filter type and its shape. If the filter is too narrow, the
signal is distorted by the filter. If the filter is too wide, multiple signals can no longer be
distinguished. Generally, the smaller the filter width and the steeper its edges, the lon-
ger the settling time and thus the longer the "Sweep Time" must be.
All resolution bandwidths are realized with digital filters. Normal (3dB) Gaussian filters
are set by default. Some communication standards require different filters.
For a list of available filter types, see Chapter 8.5.3, "Reference: List of Available RRC
and Channel Filters" , on page 474.
Bandwidth, Filter and Sweep Configuration