FFT Basics
The Fourier series states that any waveform that repeats in time can be
represented by a dc term plus a series of cosine and sine waves. The Fourier
series was developed in 1807 by the French mathematician, Jean Baptiste
Fourier, to solve thermodynamics problems. A more general form of the
Fourier series called the Fourier transform was developed later. It allows any
time domain signal, whether it is periodic or single shot, to be transformed
into the frequency domain. The fast Fourier transform (FFT) was developed
as a special algorithm that speeds up the discrete Fourier transform (DFT)
by reducing the large number of calculations that are required by DFTs.
Because an FFT runs 10 to 100 times faster than the traditional DFT, Fourier
transform calculations typically use FFTs in place of DFTs.
Oscilloscopes operate in the time domain and display waveforms with the
vertical axis representing amplitude and the horizontal axis representing
time. Because FFTs are frequency domain functions, the horizontal axis on
the display changes to represent frequency when you select FFTs.
FFT Menu
FFT Basics
21–10
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