User manual

Mathematics
R&S
®
RTO
201User Manual 1316.0827.02 ─ 06
Window type
Windowing helps minimize the discontinuities at the end of the measured signal interval
and thus reduces the effect of spectral leakage, increasing the frequency resolution.
Various different window functions are provided in the R&S RTO to suit different input
signals. Each of the window functions has specific characteristics, including some advan-
tages and some trade-offs. These characteristics need to be considered carefully to find
the optimum solution for the measurement task.
Window type Frequency
resolution
Magnitude
resolution
Measurement recommendation
Rectangular Best Worst Separation of two tones with almost equal amplitudes
and a small frequency distance
Hamming
Hann
Good Poor Frequency response measurements, sine waves, peri-
odic signals and narrow-band noise
Blackman Harris
(default)
Worst Best Mainly for signals with single frequencies to detect har-
monics
Accurate single-tone measurements
Gaussian Good Good Weak signals and short duration
Flattop2 Poor Best Accurate single-tone measurements
Kaiser Bessel Poor Good Separation of two tones with differing amplitudes and a
small frequency distance
SCPI command:
CALCulate:MATH<m>:FFT:WINDow:TYPE on page 578
Frame Arithmetics
FFT analysis can only be performed on a maximum number of values at once. If more
values must be calculated, the input signal is divided into frames, each of which is cal-
culated separately. The frames need not be disjunct, i.e. they may overlap, so that some
values have several FFT results. In this case, the arithmetic mode defines how the final
result is calculated from the individual results.
The following methods are available:
"Off"
The data of only one frame is taken into consideration. In effect, no
arithmetics are processed.
"Envelope"
Detects the minimum and maximum values for FFT calculation over all
frames. The resulting diagram shows two envelope waveforms: the
minimums (floor) and maximums (roof). These envelopes indicate the
range of all FFT values that occurred.
"Average"
The average is calculated over all frames.
SCPI command:
CALCulate:MATH<m>:FFT:FRAMe:ARIThmetics on page 582
Overlap Factor
Defines the minimum factor by which two neighboring frames overlap. If the required
number of frames to cover the input values allows for more overlap, the factor is
increased.
FFT Analysis