Displaying data in the Scope mode
R&S NRP
1144.1400.12 4.42
E-2
Background information
Points
The highest possible number of measurement points (312) corresponds exactly to the number of pixels
available on the display of the R&S NRP. The most detailed image is obtained with this value. If the
required time resolution is too high (depending on the width of the measurement window), the number
of measurement points is automatically reduced to the largest possible value (
Reduced to
display). A
closed trace is always displayed, with linear interpolation between the measurement points. Generally
312 measurement points should be set and the reduction performed automatically. See also the tip on
page 3.9.
An exception is smoothing noisy traces by decreasing the number of points. As each measurement
point represents the average power of an equivalent time interval, noise can be reduced by 30 % by
reducing the number of points by half.
Another means of reducing noise is the averaging filter (
Filter / averaging, p. 4.19), which can be
used whenever
Realtime
is not enabled. With very large averaging factors, the display will tend to re-
spond slowly.
Realtime
When the R&S NRP is in the Normal mode, averaging is always performed across a number of sweeps.
Because of the chopper amplifier (
Sampling window, p. 4.10), two sweeps are always taken into
account in calculating the measurement result, even if the averaging filter is set to 1 (
Filter / averag-
ing, p. 4.19). If the measurement points to be averaged originate from different trigger events, this can
produce a new, perhaps totally unrealistic trace. A noisy signal or a signal with more than one possible
trigger point can result in different trigger events, especially if internal triggering (
Trigger settings,
p. 4.24) is used.
Using the Realtime mode helps to set stable trigger conditions, as unstable trigger behaviour can be
detected immediately. Since the dynamic range in the Realtime mode is reduced because of larger zero
offsets, stronger noise and poorer linearity, it should be switched off when triggering is stable. If trigger-
ing is external, the Realtime mode is generally unnecessary (exception: single-shot measurement
Trigger settings p. 4.24)
.
