www.gusucode.com > signal 案例源码程序 matlab代码 > signal/SingleAndDoublePrecisionFiltersExample.m

    %% Frequency Along _x_-Axis
% Generate a quadratic chirp, |x|, sampled at 1 kHz for 2 seconds. The
% frequency of the chirp is 100 Hz initially and crosses 200 Hz at |t| = 1
% s.

% Copyright 2015 The MathWorks, Inc.


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

%%
% Compute and display the spectrogram of |x|. 
%
% * Divide the signal into sections of length 128, windowed with a Hamming
% window.
% * Specify 120 samples of overlap between adjoining sections.
% * Evaluate the spectrum at $\lfloor128/2+1\rfloor=65$ frequencies and
% $\lfloor({\tt length(x)}-120)/(128-120)\rfloor=235$ time bins.

spectrogram(x,128,120,128,1e3)

%%
% Replace the Hamming window with a Blackman window. Decrease the overlap
% to 60 samples. Plot the time axis so that its values increase from top to
% bottom.

spectrogram(x,blackman(128),60,128,1e3)
ax = gca;
ax.YDir = 'reverse';