cw3z2

N = 1024;
f1 = 500;
f2 = 1200;
fs = 8000;
n = 0 : N - 1;


noise = normrnd(0, sqrt(1), 1, N);
subplot(3, 1, 1);
plot(noise)
axis([0 (N + 10) -4 4])
title('Szum gaussowski');
xlabel('Czas');
ylabel('Amplituda');

sin1 = 0.5 * sin(2 * pi * n * f1 / fs);
sin2 = sin(2 * pi * n * f2 / fs);
sumSin = sin1 + sin2;
subplot(3, 1, 2);
plot(sumSin)
axis([0 (N + 10) -2 2])
title('Kombinacja sygnałów sinusoidalnych');
xlabel('Czas');
ylabel('Amplituda');

y = sumSin + 0.1 * noise;
subplot(3, 1, 3);
plot(y);
axis([0 (N + 10) -2 2])
title('Suma sygnałów sinusiodalnych i szumu');
xlabel('Czas');
ylabel('Amplituda');

% ---------------------------------------------------

figure;
subplot(3, 1, 1);
periodogram(noise);

subplot(3, 1, 2);
periodogram(sumSin);

subplot(3, 1, 3);
periodogram(y);

% ---------------------------------------------------

figure;
subplot(3, 1, 1);
periodogram(noise, hann(N));

subplot(3, 1, 2);
periodogram(sumSin, hann(N));

subplot(3, 1, 3);
periodogram(y, hann(N));

% ---------------------------------------------------

figure;
[pxx1, f1] = pwelch(noise, hann(256), [], N, fs);
[pxx2, f2] = pwelch(noise, hann(128), [], N, fs);
[pxx3, f3] = pwelch(noise, hann(64), [], N, fs);

subplot(3, 1, 1);
hold on;
p1 = plot(f1, 10 * log10(pxx1));
p2 = plot(f2, 10 * log10(pxx2));
p3 = plot(f3, 10 * log10(pxx3));

xlabel('Frequency (Hz)');
ylabel('PSD dB/Hz');
legend([p1 p2 p3], {'NFFT 256', 'NFFT 128', 'NFFT 64'});
grid on;
hold off;

% -------------

[pxx1, f1] = pwelch(sumSin, hann(256), [], N, fs);
[pxx2, f2] = pwelch(sumSin, hann(128), [], N, fs);
[pxx3, f3] = pwelch(sumSin, hann(64), [], N, fs);

subplot(3, 1, 2);
hold on;
p1 = plot(f1, 10 * log10(pxx1));
p2 = plot(f2, 10 * log10(pxx2));
p3 = plot(f3, 10 * log10(pxx3));

axis([-inf inf -160 -10]);
xlabel('Frequency (Hz)');
ylabel('PSD dB/Hz');
legend([p1 p2 p3], {'NFFT 256', 'NFFT 128', 'NFFT 64'});
grid on;
hold off;

% -------------

[pxx1, f1] = pwelch(y, hann(256), [], N, fs);
[pxx2, f2] = pwelch(y, hann(128), [], N, fs);
[pxx3, f3] = pwelch(y, hann(64), [], N, fs);

subplot(3, 1, 3);
hold on;
p1 = plot(f1, 10 * log10(pxx1));
p2 = plot(f2, 10 * log10(pxx2));
p3 = plot(f3, 10 * log10(pxx3));

axis([-inf inf -65 -15]);
xlabel('Frequency (Hz)');
ylabel('PSD dB/Hz');
legend([p1 p2 p3], {'NFFT 256', 'NFFT 128', 'NFFT 64'});
grid on;
hold off;