|NI-SCOPE (English | Japanese)|
In the following figure, you see the spectral representation when you sample a noninteger number of cycles of the time waveform (namely 10.25). The periodic extension of this signal creates a discontinuity similar to the figure shown in Spectral Leakage.
Notice how the energy is now spread over a wide range of frequencies, so the relative height difference between the FFT peak amplitude and the neighboring bins is reduced. This smearing of the energy is called spectral leakage.