R&S FSQ Signal Analyzer - Rohde & Schwarz

R&S FSQ Instrument Functions
Description of averaging
Analyzer Mode
Averaging is carried out over the pixels derived from the measurement samples.
Several measured values may be combined in a pixel. This means that with linear
level display the average is formed over linear amplitude values and with logarithmic
level display over levels. For this reason the trace must be measured again when
changing between LIN and LOG display mode. The settings CONT/SINGLE
SWEEP and running averaging apply to the average display analogously.
There are two methods for calculating the average. For a sweep count = 0, a running
average is calculated according to the following formula:
9 ⋅ TRACE + MeasValue
TRACE = ----------------------------------------------------------------
10
Due to the weighting between the new measured value and the trace average, past
values 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.
If the sweep count is >1, averaging takes place over the selected number of
sweeps. In this case the displayed trace is determined during averaging according
to the following formula:
Trace n
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 single sweeps for averaging.
After the selected number of sweeps the average trace is saved in the trace memory.
Until this number of sweeps is reached, a preliminary average is displayed.
After completion of averaging, i.e. when the averaging length defined by SWEEP
COUNT is attained, a running averaging is continued with CONTINUOUS SWEEP
according to the following formula:
where
n – 1
1
= -- ⋅
n
( Ti) +
∑
i = 1
Trace = new trace
Traceold = old trace
N = SWEEP COUNT
MeasValue n
( N – 1)
⋅ Traceold + MeasValue
Trace =
--------------------------------------------------------------------------------
N
The display "Sweep N of N" does not change any more until a new start is triggered.
In the SINGLE SWEEP mode, the number of sweeps is triggered with SWEEP
START. The sweeps are stopped when the selected number of sweeps is attained.
The number of the current sweep and the total number of sweeps are shown on the
display: "Sweep 3 of 200".
4.42 Operating Manual 1313.9681.12 - 01