R&S FSL Power Measurements – MEAS Key
1300.2519.12 4.81 E-11
The Adjust Settings softkey sets the video bandwidth (VBW) as a function of the channel
b
andwidth (see formula above) and the smallest possible VBW with regard to the available step
size will be selected.
• Detector
The Adjust Settings softkey selects the RMS detector. This detector is selected since it correctly
indicates the power irrespective of the characteristics of the signal to be measured. The whole IF
envelope is used to calculate the power for each measurement point. The IF envelope is digitized
using a sampling frequency which is at least five times the resolution bandwidth which has been
selected. Based on the sample values, the power is calculated for each measurement point using
the following formula:
=
=
N
1i
2
iRMS
s
N
1
P
s
i
= linear digitized video voltage at the output of the A/D converter
N = number of A/D converter values per measurement point
P
RMS
= power represented by a measurement point
When the power has been calculated, the power units are converted into decibels and the value is
displayed as a measurement point.
In principle, the sample detector would be possible as well. Due to the limited number of
measurement points used to calculate the power in the channel, the sample detector would yield
less stable results.
• Trace averaging
The Adjust Settings softkey switches off this function. Averaging, which is often performed to
stabilize the measurement results, leads to a too low level indication and should therefore be
avoided. The reduction in the displayed power depends on the number of averages and the signal
characteristics in the channel to be measured.
• Reference level
The Adjust Settings softkey does not influence the reference level. It can be separately adjusted
using the Adjust Settings softkey.
Ranges and range settings
In the Spectrum Emission Mask and Spurious Emissions measurements, a range defines a segment,
for which you can define the following parameters separately: start and stop frequency, RBW, VBW,
sweep time, sweep points, reference level, attenuator settings, and limit values. Via the sweep list, you
define the ranges and their settings (for details on settings refer to the Sweep List softkey).
The following rules apply to ranges:
• The minimum span of a range is 20 Hz.
• The individual ranges must not overlap (but need not directly follow one another).
• The maximum number of ranges is 20.
• Spectrum Emission Mask measurement only: A minimum of three ranges is mandatory.
• Spectrum Emission Mask measurement only: The reference range cannot be deleted (it is marked
in blue color).
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