The Spectrum Application (RF Measurements)
R&S
®
FPL1000
369
User Manual 1178.3370.02 ─ 11
In the default setting, the R&S
FPL1000 uses the sample detector for the noise
function. With the sample detector, you can set the trace to "Average" mode to sta-
bilize the measured values. When the RMS detector is used, trace averaging pro-
duces noise levels that are too low and cannot be corrected. Instead, increase the
sweep time to obtain stable measurement results.
Correction factors
The R&S
FPL1000 uses the following correction factors to analyze the noise density
from the marker level:
●
Since the noise power is indicated with reference to 1
Hz bandwidth, the bandwidth
correction value is deducted from the marker level. It is 10
x
lg (1
Hz/BWNoise),
where BWNoise is the noise or power bandwidth of the set resolution filter (RBW).
●
RMS detector: With the exception of bandwidth correction, no further corrections
are required since this detector already indicates the power for each point of the
trace.
●
Sample detector: As a result of video filter averaging and trace averaging, 1.05
dB
is added to the marker level. This is the difference between the average value and
the RMS value of white noise. With a logarithmic level axis, 1.45
dB is added addi-
tionally. Logarithmic averaging is thus fully taken into account, which yields a value
that is 1.45
dB lower than that of linear averaging.
●
To allow for a more stable noise display, eight trace points on each side of the mea-
surement frequency are averaged.
●
For span > 0, the measured values are averaged versus time (after a sweep).
The R&S
FPL1000 noise figure can be calculated from the measured power density
level. It is calculated by deducting the set RF attenuation (RF Att) from the displayed
noise level and adding 174 to the result.
The individual marker settings correspond to those defined in the "Marker" dialog box
(see
Chapter 6.9.2.1, "Individual Marker Setup"
on page 352). Any settings to the
marker state or type changed in the "Marker Function" dialog box are also changed in
the "Marker" dialog box and vice versa.
Marker Usage
