Some new results on the discrete bispectrum

This paper presents some new results concerning the bispectrum of sampled signals. We show that sampling a stationary signal at Fs=2B usually implies a non-zero outer triangle (OT) domain in the bispectrum due to overlapping. Moreover, we pointed out that processes (stationary or not) sampled at Fs>3B are always zero in the OT (no overlapping). Finally, we propose an empirical method for which a non-zero OT indicates that the signal is really non-stationary and we propose to combine this approach with the Hinich stationarity test (Hinich 1990, and Hinich and Messer 1995).