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© National Instruments Corporation 15 NI Spectral Measurements Toolkit User Guide
The block zoom FFT is a general-purpose technique that works best as a
post-processing method. The block zoom FFT also is useful for real-time
applications where the data rate is too high for a continuous zoom FFT to
sustain in real time. To process the entire data set, provide enough memory
to store the data until the FFT can process it. If processing every data point
is not critical, use the block zoom FFT with the latest data available.
Zoom Spectrogram
A spectrogram is the result of joint time-frequency analysis (JTFA)
processing. The Spectral Measurements Toolkit implements the short-time
Fourier transform (STFT) with a zoom FFT to give a zoom spectrogram.
The SMT Zoom STFT VI calculates FFTs on equivalent segments of your
signal at fixed time intervals. This VI applies a window to each signal
segment, calculates an FFT on the windowed segment, and arranges the
resulting FFTs in chronological order. Figure 5 illustrates the process.
Note STFT VIs are located in the <
LabVIEW
>\vi.lib\addons\Spectral
Measurements Toolset
folder.