Mathematical Problems in Engineering
Volume 2010 (2010), Article ID 618231, 14 pages
Research Article

Nonlinear Time-Varying Spectral Analysis: HHT and MODWPT

School of Information Science & Technology, East Normal University, No. 500, Dong—Chuan Road, Shanghai 200241, China

Received 31 January 2010; Accepted 19 March 2010

Academic Editor: Cristian Toma

Copyright © 2010 Pei-Wei Shan and Ming Li. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Time-frequency distribution has received a growing utilization for analysis and interpretation of nonlinear and nonstationary processes in a variety of fields. Among them, two methods, such as, the empirical mode decomposition (EMD) with Hilbert transform (HT) which is termed as the Hilbert-Huang Transform (HHT) and the Hilbert spectrum based on maximal overlap discrete wavelet package transform (MODWPT), are fairly noteworthy. Comparisons of HHT and MODWPT in analyzing several typical nonlinear systems and examinations of the effectiveness using these two methods are illustrated. This study demonstrates that HHT can provide comparatively more accurate identifications of nonlinear systems than MODWPT.