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Biosignal and Biomedical Image Processing MATLAB-Based Applications phần 6

Đây là bộ sách nói về cách ứng dụng Matlab vào tất cả các lĩnh vực | Time-Frequency Analysis 171 Figure 6.11 The determining function of the Rihaczek-Margenau distribution. Example 6.5 Compare the Choi-Williams and Rihaczek-Margenau distributions for both a double sinusoid and chirp stimulus. Plot the Rihaczek-Margenau determining function and the results using 3-D type plots. Example 6.5 and various figures Example of the use of Cohen s class distributions applied to both sequential sinusoids and a chirp signal Q. clear all close all global G Set up constants. Same as in previous examples fs 500 Sample frequency N 256 Signal length fl 20 First frequency in Hz f2 100 Second frequency in Hz Q. Construct a step change in frequency signal_type input Signal type 1 sines 2 chirp if signal_type 1 tn 1 N 4 fs x zeros N 4 1 sin 2 pi f1 tn sin 2 pi f2 tn Note the code for the Rihaczek-Margenau determining function and several other determining functions can be found on disk with the software associated with this chapter. Copyright Marcel Dekker Inc. All rights reserved. Marcel Dekker Inc. 270 Madison Avenue New York New York 10016 TLFeBOOK 172 Chapter 6 zeros N 4 1 else tn 1 N fs x chirp tn f1 .5 f2 end Ox Ox Get desired distribution type input Enter type choi BJC R_M WV s Ox x hilbert x Get analytic function CD f t cohen x fs type Cohen s class of transformations CD abs CD Take magnitude Plot distribution in figure 3-D mesh t f CD view 85 40 Change view for better display .3D labels and scaling. heading type Distribution Construct appropriate eval title heading title and add to plot Ox Ox figure contour t f CD Plot distribution as a contour plot xlabel Time sec ylabel Frequency Hz eval title heading This program was used to generate Figures 6.11-6.15. In this chapter we have explored only a few of the many possible timefrequency distributions and necessarily covered only the very basics of this extensive subject. Two of the more important topics that were not covered here are the estimation of instantaneous frequency from the time-frequency