PRACTICAL MATLAB® FOR ENGINEERS PRACTICAL MATLAB

84 Practical MATLAB® Applications for Engineers

ylabel(‘Amplitude’);xlabel(‘time index n’)

title(‘f(n) is decimated with M=10’)

figure(2); % up-sample with L = 2, 4, 10

subplot(2,2,1)

stem(n,f); hold on; plot(n,f,n,yzero(1:100))

title(‘f(n) vs n’);ylabel(‘Amplitude’);

xlabel(‘time index n’);

subplot(2,2,2)

gL2 = interp(f,2);

nL2 = 0:100*2-1;

stem(nL2,gL2(1:200));hold on; plot(nL2,yzero(1:200));

title(‘f(n) is upsampled with L=2’); ylabel(‘Amplitude’);

xlabel(‘time index n’);

subplot(2,2,3)

gL4 = interp(f,4);

nL4 = 0:100*4-1;

stem(nL4,gL4(1:400)); hold on;

plot (nL4,yzero(1:400));

ylabel(‘Amplitude’);xlabel(‘time index n’);

title(‘f(n) is upsampled with L=4’)

subplot(2,2,4)

gL10= interp(f,10);

nL10 = 0:100*10-1;

stem(nL10,gL10(1:1000));hold on;

ylabel(‘Amplitude’); xlabel(‘time index n’)

title(‘f(n) is upsampled with L=10’)

figure(3)

% re-sample by ratio of L=3/M=2 & L=2/M=3

subplot(3,1,1)

stem(n,f);hold on; plot(n,f,n,yzero(1:100))

title(‘f(n) vs n’);

ylabel(‘Amplitude’); xlabel(‘time index n’);

subplot(3,1,2)

gr32= resample(f,3,2);

nr32 = 0:100*3/2-1;yzeros = zeros(1,length(nr32));

stem(nr32,gr32(1:100*3/2));hold on;plot(nr32,yzeros);

ylabel(‘Amplitude’); xlabel(‘time index n’);

subplot(3,1,3)

gr23 = resample(f,2,3);

nr23 = 0:100*2/3-1;

yzero = zeros(1,length(nr23));

stem(nr23,gr23(1:100*2/3));

hold on;plot(nr23,yzero);

axis([0 65 -5 5]);

ylabel(‘Amplitude’); xlabel(‘time index n’)

Back in the command window, the script fi le up_down_samples is executed and the

results are shown in Figures 1.70 through 1.72.