FFT Analyzer Basic FAQ

While the DFT (FFT) principle allows obtaining spectral information in a frequency band up to half the sampling frequency fs, actual FFT analyzers use a smaller bandwidth (1/2.56 of fs) as their actual analysis range to reduce aliasing errors. This is called the frequency range frange.

In other words;

（1）

This is the relationship. The reason for using 2.56 is that the number of calculation points in the FFT is a power of 2, so the frequency range is rounded to a decimal value.

Ono Sokki 's FFT analyzer usually determines the frequency range first, so the sampling frequency can be determined in reverse from equation (1). For example, when the frequency range is 20 kHz, the sampling frequency is 51.2 kHz.