Common Analysis and Display Functions
R&S
®
FSW
456
User Manual 1173.9411.02 ─ 19
If the level range or reference level is changed, the R&S
FSW automatically adapts the
trace data to the changed display range. This allows an amplitude zoom to be made
after the measurement in order to show details of the trace.
7.3.1.3
How Many Traces are Averaged - Sweep Count + Sweep Mode
In "Average" trace mode, the sweep count and sweep mode determine how many
traces are averaged. The more traces are averaged, the smoother the trace is likely to
become.
The algorithm for averaging traces depends on the sweep mode and sweep count.
●
sweep count = 0
(default)
–
In
"Continuous Sweep"
mode, a continuous average is calculated for 10
sweeps, according to the following formula:
10
*
9
MeasValue
Trace
Trace
old
Fig. 7-5: Equation 1
Due to the weighting between the current trace and the average trace, past val-
ues have practically no influence on the displayed trace after about ten
sweeps. With this setting, signal noise is effectively reduced without need for
restarting the averaging process after a change of the signal.
–
In
"Single Sweep"
mode, the current trace is averaged with the previously
stored averaged trace. No averaging is carried out for the first sweep but the
measured value is stored in the trace memory. The next time a sweep is per-
formed, the trace average is calculated according to the following formula:
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
Fig. 7-6: 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.
Trace Configuration
