The Spectrum Application (RF Measurements)
R&S
®
FPL1000
320
User Manual 1178.3370.02 ─ 09
For an optimal sweep rate, it is recommended that you set the "Sweep Time" to "Auto",
as well.
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.
7.6.1.6
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 7.6.3, "Reference: List of Available RRC
Normal (3 dB) Gaussian filters
Gaussian filters provide a good compromise between steep edges and a short settling
time. This filter is suitable for most measurement tasks and is used by default.
The available Gaussian (3 dB) filters are listed in the R&S
FPL1000 data sheet.
Channel filters
Channel filters are fairly steep but require a long settling time; they are useful for pulse
measurements in the time domain.
7.6.1.7
How Long the Data is Measured: Sweep Time
Each filter has a settling time that must be awaited in order to obtain correct results.
Since the resolution bandwidth and video bandwidth define the filter, the smaller of the
two determines the minimum "Sweep Time" required for the measurement. Allowed
values depend on the ratio of span to RBW and RBW to VBW.
If the selected "Sweep Time" is too short for the selected bandwidth and span, level
measurement errors will occur. In this case, the R&S
FPL1000 displays the error mes-
sage "Sweep time too low" and marks the indicated "Sweep Time" with a red bullet.
Furthermore, a status bit indicates an error.
(For more information see
"STATus:QUEStionable:TIMe Register"
The "Sweep Time" can be coupled to the span (not zero span), video bandwidth (VBW)
and resolution bandwidth (RBW) automatically. If the span, resolution bandwidth or
video bandwidth is changed, the "Sweep Time" is automatically adjusted.
Bandwidth, Filter and Sweep Configuration
