Frequency aliasing refers to the phenomenon that high-frequency and low-frequency components are confused due to the change of sampling signal spectrum. The sampling frequency is not high enough, and the sampling point represents the sampling value of both low-frequency signals and high-frequency signals. In signal reconstruction, the high-frequency signal is replaced by the low-frequency signal, and the two waveforms completely overlap, resulting in serious distortion.

Frequency aliasing is an important concept and a unique phenomenon in digital signal processing, which is caused by discrete sampling in digital signals. Any discrete sampling with equal step size will definitely produce frequency aliasing. Frequency aliasing will produce false frequency and false signal, which will seriously affect the measurement results. The sampling frequency is less than twice the frequency of the highest component to be analyzed in the analog signal.