Aliasing & the Nyquist theorem (interactive)

960×700 iframe (compact)

Fs (Hz) f (Hz) f slider (0..3·Fs) Phase (deg) Duration (s) Show

Time: dense “continuous” sine + sampled points at Fs

Discrete samples x[n] (stems)

Nyquist: if the signal has no content above Fs/2, it can be reconstructed. If f > Fs/2, it aliases (folds) into a lower frequency.

True f, Nyquist Fs/2, and alias frequency

Different analog frequencies separated by multiples of Fs can produce identical samples.