Common measurement settings
R&S
®
FSVA3000/ R&S
®
FSV3000
466
User Manual 1178.8520.02 ─ 08
6.5.1.4
Coupling span and RBW
The resolution bandwidth can be coupled to the span setting, either by a manually
defined factor or automatically. If the span is changed, the resolution bandwidth is
automatically adjusted. The automatic coupling adapts the resolution bandwidth to the
currently set frequency span/100.
The 6 dB bandwidths 200 Hz, 9 kHz and 120 kHz and the available channel filters are
not changed by the coupling.
With a span/RBW ratio of 100 and a screen resolution of 1000 pixels, each frequency
in the spectrum is displayed by 10 pixels. A span/RBW ratio of 1000 provides the high-
est resolution.
A higher span/RBW ratio (i.e. low RBW values and large frequency spans), however,
results in large amounts of data.
6.5.1.5
How data is measured: the sweep type
In a standard analog
frequency sweep
, the local oscillator of the analyzer sweeps the
applied signal quasi analog from the start to the stop frequency to determine the fre-
quency spectrum.
Alternatively, the analyzer can sample signal levels over time at a defined frequency
and transform the data to a spectrum by Fast Fourier Transformation (
FFT
). Although
this measurement method requires additional calculations, it can provide results much
faster than the frequency sweep, in particular for small RBWs.
Which sweep mode is appropriate for the current measurement depends on the span,
RBW, VBW and "Sweep Time" settings. By default ("Auto" sweep type), the
R&S
FSV/A automatically uses the sweep type with the highest sweep rate depending
on these measurement settings.
For EMI measurements, the R&S
FSV/A automatically selects sweep mode for auto
sweep type. You can also select sweep mode manually.
Restrictions for FFT mode
FFT mode is not available when using 5-pole filters, channel filters or RRC filters, or
the quasi peak detector. In this case, sweep mode is used.
The same applies when an external generator is active (with the optional External Gen-
erator Control).
FFT mode is not available if if CISPR detectors are used.
(See
Chapter 5.13.3.2, "Detectors and dwell time"
Restrictions for Sweep mode
For gated measurements in sweep mode, only external gating trigger sources and the
"Edge" gating mode are supported, see
Bandwidth, filter and sweep configuration
