Basic FAQ for FFT Analyzer

The principle of DFT (FFT) allows us to obtain spectral information up to half of the sampling frequency fs, but in actual FFT analyzers, to reduce aliasing errors, a bandwidth smaller than 1/2 (fs of 1/2.56) is used as the actual analysis range. This is called frequency range frange.

That is;

（1）

This is the relationship. The reason for using 2.56 is that the number of calculation points for the FFT is a power of two, which allows for a clean decimal value for the frequency range.

The FFT analyzer from Ono Sokki typically determines the frequency range first, so from equation (1), the sampling frequency can be known. For example, when the frequency range is 20 kHz, the sampling frequency will be 51.2 kHz.