Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: A New Approach for Estimation of Instantaneous Mean Frequency of a Time-Varying Signal | EURASIP Journal on Applied Signal Processing 2005 17 2848-2855 2005 Hindawi Publishing Corporation A New Approach for Estimation of Instantaneous Mean Frequency of a Time-Varying Signal Sridhar Krishnan Department of Electrical and Computer Engineering Ryerson University Toronto ON Canada M5B 2K3 Email krishnan@ Received 1 June 2004 Revised 30 December 2004 Recommended for Publication by John Sorensen Analysis of nonstationary signals is a challenging task. True nonstationary signal analysis involves monitoring the frequency changes of the signal over time . monitoring the instantaneous frequency IF changes . The IF of a signal is traditionally obtained by taking the first derivative of the phase of the signal with respect to time. This poses some difficulties because the derivative of the phase of the signal may take negative values thus misleading the interpretation of instantaneous frequency. In this paper a novel approach to extract the IF from its adaptive time-frequency distribution is proposed. The adaptive time-frequency distribution of a signal is obtained by decomposing the signal into components with good time-frequency localization and by combining the Wigner distribution of the components. The adaptive time-frequency distribution thus obtained is free of crossterms and is a positive time-frequency distribution but it does not satisfy the marginal properties. The marginal properties are achieved by applying the minimum cross-entropy optimization to the time-frequency distribution. Then IF may be obtained as the first central moment of this adaptive time-frequency distribution. The proposed method of IF estimation is very powerful for applications with low SNR. A set of real-world and synthetic signals of known IF dynamics is tested with the proposed method as well as with other common time-frequency distributions. The simulation shows that the method successfully extracted the IF of the signals. Keywords and phrases instantaneous .
