PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

Fourier and Laplace 427

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

105

100

10 −^5

10 −^10

10 −^15

10 −^20

Power Spectral Density (PSD)

Frequency

FIGURE 4.73

PSD plot of Example 4.17.

power1 = norm(ft).^2/length(t);

power2 = sum(abs(ft).^2)/length(t);

disp(‘*******************************************’)

disp(‘ ********** R E S U L T S**********’)

disp(‘*********************************************’)

disp(‘The power of f(t)(in watts) using the norm function is =’)

disp(power1)

disp(‘The power of f(t) (in watts) using the sum/abs functions is =’)

disp(power2)

disp(‘*********************************************’)

Ps = spectrum(ft,1024);

specplot(Ps)

title(‘Power Spectral Density (PSD)’)

The above script fi le powers is executed and the results are as follows (Figure 4.73):

>> powers

************************************************************

*********************R E S U L T S ********************

*************************************************************

The power of f(t) (in watts) using the norm function is =

10.0040

The power of f(t) (in watts) using the sum/abs functions is =

10.0040