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2
Scope Features and Functions
FFT Settings
Selecting an FFT Window
There are four FFT windows. Each window has trade-offs between frequency
resolution and amplitude accuracy. Use the following guidelines to select the best
window.
Table 2-8
Comparison between the four FFT windows
Window
Rectangular
Hanning
Hamming
Blackman Harris
Flattop
The Random Dither option enables the reduction of noise floor. To enable this
option, click on the Random Dither checkbox.
Horizontal scaling is automatically calculated. It will span the entire range of
spectrum horizontally for best-fit display.
Vertical Scale option allows you to scale your spectrum vertically. Vertical Offset
allows you to adjust the vertical offset of your spectrum.
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Characteristics
Best frequency resolution, worst magnitude
resolution. This is essentially the same as no
window.
Better frequency, poorer magnitude
accuracy than Rectangular. Hamming has
slightly better frequency resolution than
Hanning.
Best magnitude, worst frequency resolution. Single frequency waveforms, to find higher order
Best amplitude accuracy, poor frequency
resolution when compared with the Hanning
window.
Best for measuring
Transients or bursts, the waveform levels before and
after the event are nearly equal. Equal-amplitude sine
waves with fixed frequencies. Broadband random noise
with a relatively slow varying spectrum.
Sine, periodic, and narrow-band random noise.
Transients or bursts where the waveform levels before
and after the events are significantly different.
harmonics.
Amplitude of single frequency components with little
nearby spectral energy in the signal.
Keysight U2701A/U2702A User's Guide
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