Spectrum analysis
R&S
®
RTP
402User Manual 1337.9952.02 ─ 12
9 Spectrum analysis
The R&S RTP provides two ways of spectrum analysis:
●
Basic FFT calculation, which is included in the firmware
●
Spectrum analysis option R&S RTP-K37, which provides a wide range of analysis
possibilities, for example, spectrogram, cursor and automatic measurements.
9.1 FFT analysis
9.1.1 Fundamentals of FFT analysis
During FFT analysis, a signal in the time domain is converted to a spectrum of frequen-
cies. As a result, either the magnitude or the phase of the determined frequencies can
be displayed. FFT analysis can be restricted to an extract of the original time base, and
the results display can be restricted to a specified frequency range.
t[s]
FFT
f[Hz]
Frames/Segments
To convert the time domain signal to a frequency spectrum, an FFT (Fast Fourier
Transformation) unit is used which converts a vector of input values into a discrete
spectrum of frequencies.
Conventional oscilloscopes calculate one FFT per capture. The R&S RTP can calcu-
late multiple FFTs per capture by dividing one capture into several segments, or
frames. Thus, the R&S RTP can visualize how the frequency content of a signal
changes over time which helps to detect intermittent or sporadic signal details. Further-
more, the R&S RTP allows consecutive frames to overlap. This is especially useful in
conjunction with window functions since it enables a gap-free frequency analysis of the
signal.
FFT analysis
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