The Spectrum Application (RF Measurements)
R&S
®
FPL1000
391
User Manual 1178.3370.02 ─ 09
2
MeasValue
Trace
Trace
old
The averaged trace is then stored in the trace memory.
●
sweep count = 1
The currently measured trace is displayed and stored in the trace memory. No
averaging is performed.
●
sweep count > 1
For both
"Single"
sweep mode and
"Continuous"
sweep mode, averaging takes
place over the selected number of sweeps. In this case the displayed trace is
determined during averaging according to the following formula:
1
1
)
(
1
n
i
n
i
n
MeasValue
T
n
Trace
Figure 7-53: Equation 2
Where n is the number of the current sweep (n = 2 ... Sweep Count).
No averaging is carried out for the first sweep but the measured value is stored in
the trace memory. With increasing n, the displayed trace is increasingly smoothed
since there are more individual sweeps for averaging.
After the selected number of sweeps, the average trace is saved in the trace mem-
ory. Until this number of sweeps is reached, a preliminary average is displayed.
When the averaging length defined by the "Sweep Count" is attained, averaging is
continued in continuous sweep mode or for "Continue Single Sweep" according to
the following formula:
N
MeasValue
Trace
N
Trace
old
*
)
1
(
Where N is the sweep count
How Trace Data is Averaged - the Averaging Mode
When the trace is averaged over several sweeps (Trace mode: "Average"), different
methods are available to determine the trace average.
With logarithmic averaging, the dB values of the display voltage are averaged or sub-
tracted from each other with trace mathematical functions.
With linear averaging, the level values in dB are converted into linear voltages or pow-
ers before averaging. Voltage or power values are averaged or offset against each
other and reconverted into level values.
For stationary signals, the two methods yield the same result.
Logarithmic averaging is recommended if sinewave signals are to be clearly visible
against noise since with this type of averaging noise suppression is improved while the
sinewave signals remain unchanged.
For noise or pseudo-noise signals, the positive peak amplitudes are decreased in loga-
rithmic averaging due to the characteristic involved. The negative peak values are
Trace Configuration
