National Instruments NI Spectral Measurements Toolkit User Manual page 16

1.0
0.8
0.6
0.4
0.2
0.0
–0.2
–0.4
–0.6
0
FFT
F
NI Spectral Measurements Toolkit User Guide
10 20 30
FFT
The SMT Config Zoom STFT VI specifies the spectrogram in terms of
its center frequency, frequency span, and time span. The frequency span
controls the FFT zoom. If the center frequency is 10 MHz and the span is
2 MHz, the SMT Config Zoom STFT VI calculates the spectrogram from
9 MHz to 11 MHz. The time span specifies the time interval from the center
of the first window to the center of the last window. The VI also has
advanced parameters for specifying the spectrogram, including window,
resolution bandwidth, RBW definition, frequency points, time points, and
Time Span
40 50
Time (µ s )
T
Figure 5. Spectrogram Process Example
16
Window
Signal
60 70 75
ni.com