lab3_ptk

clear; clc; clf; close;
f1 = 1000;
f2 = 1400;
fc = 100000; % 220000
Fs = 8 * fc;
N = 3200;
n = 0 : N-1;
m = 1; % m = [0, 0.25, 0.5, 1, 1.2];
%x = 5*sin(2*pi * (f1/Fs) * n) + 0*sin(2*pi * (f2/Fs) * n);
A = linspace(0, 1, 800);
B = linspace(-1, 0, 800);
x = [A B A B];

x2n = x/max(abs(x));
s = 10*(1 + m*x2n) .* cos(2*pi * fc/Fs * n);
widmo = abs(fft(s));

subplot(311), plot(n/N * Fs ,x), grid;
subplot(312), plot(n/N * Fs, s,  '-x'), grid; % sygnal zmodulowany
subplot(313), stem(n/N * Fs, widmo,  '-x'), grid;
axis([0 Fs/2 0 max(widmo)]);

figure;

% znak = (1 + sign(s)) / 2;
% swypr = s .* znak;
%
% [B, A] = butter(1,5000 / (Fs/2));
% u = filter(B, A, swypr);
% subplot(311), plot(n, u), grid;
% subplot(312), plot(n, x), grid;
% subplot(313), plot(n, swypr), grid;


%znak = (1 + sign(s)) / 2;
%swypr = s .* znak;
[B, A] = butter(4, 5000 / (Fs/2));
v = s .* cos(2*pi * fc/Fs * n);
u = filter(B, A, v);
subplot(311), plot(n, u), grid;
subplot(312), plot(n, x), grid;
%subplot(313), plot(n, swypr), grid;