TIME – FREQUENCY ANALYSIS OF NON-STATIONARY MAGNETIC FIELDS
Beata Pałczyńska
Abstract:
The paper considers applying the quadratic joint time – frequency transform for the spectral analysis of the non-stationary magnetic fields. The general properties, advantages and disadvantages of the quadratic algorithms from Cohen’s class like the short – time Fourier transform (STFT) spectrogram and the pseudo Wigner – Ville (PWV) distribution as well as the adaptive spectrogram are discussed. The selected results of the off-line time-frequency analysis of the recorded signals of magnetic field of ship bow thrusters drive with frequency converter are presented.
Performed time-frequency analysis enabled the signal identification in time periods. If the frequency contents of the analyzed signal don’t change rapidly, then the STFT spectrogram can be applied with relatively wide window function, to obtain a good frequency resolution. The PWV distribution is useful for analyzing signals that have widely separated components for which a fine time-frequency resolution is required. The adaptive algorithm is characterized by the most accurate detection of investigated nonstationary components, but it requires more computation time, which is suitable only for off-line analysis.
Exploring New Frontiers of Instrumentation and Methods for Electrical and Electronic Measurements
Title:
XVIth IMEKO TC4 International Symposium on Electrical Measurements and Instrumentation (together with 13th IMEKO TC4 Workshop on ADC Modelling and Testing)
