The bispectral aliasing test

Digital signal processing of continuous signals requires sampling of the continuous signal. When sampling continuous signals it is important to avoid the effect called aliasing. Aliasing causes signals at particular frequencies to appear, erroneously, as signals of different frequencies. Consequently, it is important that before any digital signal processing is performed, the sampled signal is known to be free of aliasing. A published test based on the bispectrum purports to be able to detect aliasing of an already sampled signal. The authors provide counter examples to demonstrate that this previously published test for aliasing is not valid in practice.