Transform of modulated oscillations



next up previous
Next: Inverse transform Up: No Title Previous: Analysis of a

Transform of modulated oscillations

As pointed out earlier, if the data are periodic, Fourier analysis is best and there is no need for wavelet transforms. Thus, it is time we show the result of wavelet analysis on artificial data with controled non-periodicity to illustrate some of the salient features.

First, we show the graph of with its Mexican-hat wavelet transform (Fig 12).




Figure 12: g2-wavelet map of showing the gradual shift to shorter durations.

The wavelet map shows the gradual shift of local maxima and minima toward shorter durations, as expected. Next, a sine wave was modulated both in intensity and in frequency. The corresponding shifts in duration and energy are shown on the next figure (Fig. 13).




Figure 13: g2-wavelet map of a strongly modulated oscillation.


Finally, a composite signal was generated by superposition of excerpts of sine waves at different frequencies and random noise. Only positive contour lines of a Mexican-hat wavelet map (Fig. 14) are shown for clarity.




Figure 14: g2-wavelet map of an intermittent signal.



next up previous


Jacques Lewalle
Mon Nov 13 10:51:25 EST 1995