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Scalogram of Hyperbolic Chirp

Use Signal Analyzer to display a hyperbolic chirp and its scalogram. This example requires a Wavelet Toolbox™ license.

Generate a signal sampled at 1 kHz for 1 second. The signal consists of two hyperbolic chirps. One of the chirps is active between 0.1 second and 0.68 second. The other chirp has twice the amplitude and one-third of the instantaneous frequency of the first chirp. The second chirp is active between 0.1 second and 0.75 second.

n = 1000;
t = (0:n-1)/n;

ff = [1 2]*(sin(pi*[15 5]'./(t-0.8001)).*(t>0.1 & t<[0.68 0.75]'));

The chirp is modulated by an envelope that starts at 0.1 second and is nonzero for 0.7 second.

envl = zeros(size(t));
M = 0.7*n;
envl(n/10+(1:M)) = tukeywin(M,0.8);

nw = ff.*envl;

Display the signal in Signal Analyzer. Click Time-Frequency ▼ on the Display tab and select Scalogram.

signalAnalyzer(nw,'TimeValues',t)

On the Scalogram tab, set the Voices Per Octave to the maximum value. Set the lower magnitude limit to 0.5.

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