Agilent Technologies 93000 SOC Series Training Manual page 565

Leakage appears in a
FFT spectrum, if the
assumed waveform
differs from the
original waveform.
Coherent sampling
avoids leakage.
The FFT algorithm calculates frequency components which "leak"
into the pure spectrum. This is illustrated in the following picture.
Correct and Incorrect Time Record
Leakage makes it impossible to detect minor signal components.
The optimal way to avoid leakage is to sample coherently.
Coherent sampling ensures that the time record includes a whole
number of signal periods (the UTP). These periods can be
seamlessly concatenated.
Appendix A
565