Wavelet Transform and Scalogram of Variable Frequency.

Cuthbert Nyack
The applet shows the scalogram of signals whose frequency changes with time. 3 signals are shown, The Chirp signal with frequency changing linearly with time, the Stepped frequency signal with the frequency changing in steps and the FM signal where the frequency changes sinusoidally in time. Fourier Analysis of these signals gives a set of constant amplitude sinusoids which extend from -¥ to +¥. Wavelet analysis is capable of following the frequency as it varies.

Applet below shows the scalogram of a chirp signal, with frequency changing from w1 to w2.



When enabled, the following gif image show how the applet should appear:-
The applet shows a scalogram of a signal whose frequency is stepped in time. The frequency can have 3 values w1, w2, and (w1 + w2)/2.0.



When enabled, the following gif image show how the applet should appear:-
The applet shows the scalogram of a signal whose frequency changes sinusoidally with time between w2 - mod * w1 and w2 + mod * w1.



When enabled, the following gif image show how the applet should appear:-

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COPYRIGHT 2007 Cuthbert Nyack.