E.11Alias and Nyquist Zone

Enter the input frequency and sample rate to see where the signal and its harmonics land in the first Nyquist zone.

Results

Alias frequency
—
Nyquist zone
—
Spectrum
—
2nd harmonic
—
3rd harmonic
—
4th harmonic
—
5th harmonic
—

    Formulas

    Nyquist zone
    n = ⌊f / (fs/2)⌋ + 1
    Alias
    f_alias = |f − fs · round(f / fs)|
    Inversion
    Spectrum is inverted in even-numbered zones

    Undersampling

    Signals above half the sample rate fold into the first Nyquist zone (0 – fs/2). This is used deliberately in IF sampling (undersampling), but harmonics and unwanted signals fold in the same way and can land in band. When planning frequencies, check that the aliases of the fundamental and its harmonics are well separated from each other and from the band of interest.

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