Howtosignalprocessing
- How does aliasing affect FFT?
- What is folding and aliasing?
- What is the formula for folding frequency?
- What are the effects of aliasing?
How does aliasing affect FFT?
Recognizing Aliasing in the FFT
It is common to have acquired signals with a fundamental frequency less than half the sample rate, but the harmonics of that signal may be greater than half the sample rate and they will alias. This shows up in the FFT as frequencies that fold back into the display.
What is folding and aliasing?
Spectral Aliasing (Figure 1) and Folding (Figure 2) are phenomena in which NMR peaks occur at frequencies that are different from their real frequencies. Such peaks are called folded or aliased peaks, depending on the applied method of data acquisition.
What is the formula for folding frequency?
(Also called Nyquist frequency.) The highest frequency that can be measured using discretely sampled data. It is given by nf (rad s-1) = π/Δt, where nf is the Nyquist frequency and t is the time increment between observations.
What are the effects of aliasing?
Aliasing is an undesirable effect that is seen in sampled systems. When the input frequency is greater than half the sample frequency, the sampled points do not adequately represent the input signal. Inputs at these higher frequencies are observed at a lower, aliased frequency.
