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    %% Power Spectral Densities of Chirps
% Compute and display the PSD of each segment of a quadratic chirp that
% starts at 100 Hz and crosses 200 Hz at _t_ = 1 s. Specify a sample rate
% of 1 kHz, a segment length of 128 samples, and an overlap of 120 samples.
% Use 128 DFT points and the default Hamming window.

% Copyright 2015 The MathWorks, Inc.


%%

t = 0:0.001:2;
x = chirp(t,100,1,200,'quadratic');

spectrogram(x,128,120,128,1e3,'yaxis')
title('Quadratic Chirp')

%%
% Compute and display the PSD of each segment of a linear chirp that starts
% at DC and crosses 150 Hz at _t_ = 1 s. Specify a sample rate of 1 kHz, a
% segment length of 256 samples, and an overlap of 250 samples. Use the
% default Hamming window and 256 DFT points.

t = 0:0.001:2;
x = chirp(t,0,1,150);

spectrogram(x,256,250,256,1e3,'yaxis')
title('Linear Chirp')

%%
% Compute and display the PSD of each segment of a logarithmic chirp
% sampled at 1 kHz that starts at 20 Hz and crosses 60 Hz at _t_ = 1 s.
% Specify a segment length of 256 samples and an overlap of 250 samples.
% Use the default Hamming window and 256 DFT points.

t = 0:0.001:2;
x = chirp(t,20,1,60,'logarithmic');

spectrogram(x,256,250,[],1e3,'yaxis')
title('Logarithmic Chirp')

%%
% Use a logarithmic scale for the frequency axis. The spectrogram becomes a
% line.

ax = gca;
ax.YScale = 'log';