Fast Fourier Transforms
3–30
TDS 420A, TDS 430A, TDS 460A & TDS 510A User Manual
frequencies. Best type for measuring the frequency spectrum of
non-repetitive signals and measuring frequency components near DC.
Hamming — Very good for resolving frequencies that are very close to
the same value with somewhat improved amplitude accuracy over the
rectangular window.
Hanning — Very good for measuring amplitude accuracy but degraded
for resolving frequencies.
Blackman-Harris — Best window for measuring the amplitude of
frequencies but worst at resolving frequencies.
See Selecting a Window, on page 3–39, provides in depth information on
choosing the right window for your application.
9. If you did not select Phase (deg) or Phase (rad) in step 7, skip to step 12.
Phase suppression is only used to reduce noise in phase FFTs.
10. If you need to reduce the effect of noise in your phase FFT, press Suppress
phase at amplitudes <
(side).
11. Use the general purpose knob or the keypad to adjust the phase suppression
level. FFT magnitudes below this level will have their phase set to zero.
See Adjust Phase Suppression, on page 3–38, provides additional informa-
tion on phase suppression.
12. Press OK Create Math Wfm
(side) to display the FFT of the waveform you
input in step 1 (see Figure 3–17).
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