Waveform analysis
R&S
®
RTM3000
110User Manual 1335.9090.02 ─ 09
The constant dx defines how many samples are averaged before using the average in
derivative calculation. The optimal value depends on the signal's frequency, the sig-
nal's noise and the configured record length and time scale (timebase). Recommended
values are between 50 and 5000. Select a smaller value for smaller timebases or
smaller record lengths.
7.2.5 Filters
The R&S RTM3000 provides several ways to filter the input signal:
●
Lowpass filter by selecting a bandwidth limit in the acquisition path (vertical chan-
nel settings), see Chapter 5.3.3, "Vertical settings", on page 54.
●
Create a filtered math waveform (lowpass or highpass). Filtered math waveforms
are described below.
To create a lowpass or highpass, the infinite impulse response filter (IIR) is used. The
filter require an additional setting: the cut-off frequency "BW".
Table 7-1: Available math filters
Low pass LP(Source,BW)
Calculates a low-pass filtered waveform of the source waveform using 2nd order
IIR. The cut-off frequency BW is set as a const value. Signal components with fre-
quencies higher than the cut-off frequency are attenuated significantly.
High pass HP(Source,BW)
Calculates a high-pass filtered waveform of the source waveform using 1st order
IIR. The cut-off frequency BW is set as a constant value. Signal components with
frequencies below the cut-off frequency are attenuated significantly.
IIR filter need a settling time. During settling time, the filtered waveform is not shown
on the screen, thus the filtered waveform is shorter than the source waveform. The
duration of the settling time depends on the cut-off frequency "BW". The lower the limit,
the longer the settling time, an the shorter the filtered waveform.
The cut-off frequency is limited and depends on the horizontal resolution of the display
data. If the selected cut-off frequency exceeds the limit, the limit frequency is shown in
red in the math waveform label.
7.2.6 Tracks
The track is a waveform that shows measurement values in time-correlation to the
measured signal. It is the graphical interpretation of measurement values of a single
acquisition. The R&S RTM3000 can track frequency, period, pulse width, and duty
Mathematics
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