Plotting undersampled signals

testUndersampling.m

pkg load signal;

FS = 48000;
MULTIPLE = 100;
CONT_FS = MULTIPLE * FS;

F = 20000; % 20kHz


tCont = transpose(0:1/CONT_FS:5 * 1/F);

fundCont = 0.5 * sin(2*pi *F * tCont);

h2Cont = 0.25 * sin(2*pi *2 *F * tCont);

framesCont = [tCont, fundCont + h2Cont];


plot(framesCont(:, 1), framesCont(:, 2));
hold on;


% downsampling to FS without filtering - simply keeping every MULTIPLEth sample
framesSampled = downsample(framesCont, MULTIPLE);
stem(framesSampled(:, 1), framesSampled(:, 2), '.o', 'linewidth', 2, 'markersize', 20);




F_SPUR = 8000;
spuriousCont = -0.125 * sin(2*pi *F_SPUR * tCont);
framesCont = [tCont, fundCont + 0.5 * h2Cont + spuriousCont];

plot(framesCont(:, 1), framesCont(:, 2));



% sampling at FS - keeping every MULTIPLEth sample
framesSampled = downsample(framesCont, MULTIPLE);
stem(framesSampled(:, 1), framesSampled(:, 2), '.x', 'linewidth', 2, 'markersize', 20);
hold off;