1.2 Signal Processing

function one_2()
    clc;
    clear;

    global Fs;
    Fs = 1000;

    samples = 200;

    t = 0:1/Fs:1/2*samples*1/Fs;
    x_n = cos(125.*pi.*t).*cos(325.*pi.*t)
    L = 200;

    plot_signal(x_n, "Amplitude", "Samples", "Sampled signal at f_s = 1 KHz sampling rate", false, NaN, 1);

    t = 0:1/Fs:samples*1/Fs;
    x_n = cos(125.*pi.*t).*cos(325.*pi.*t)

    plot_spectrum(x_n, L, 2);
    plot_spectrum(x_n, L/2, 3);
end

function plot_signal(x, ylab, xlab, tl, isFreq, N, p)
    global Fs;
    subplot(3,1,p);
    if (isFreq == true)
        stem((-N/2:N/2-1)*Fs/N, x, 'b.-', 'LineWidth', 2, 'MarkerSize', 15)
    else
        stem(0:numel(x)-1, x, 'r.-', 'LineWidth', 2, 'MarkerSize', 15)
    end
    title(tl);
    xlabel(xlab);
    ylabel(ylab);
    grid on;
end

function plot_spectrum(x, N, p)
    fx = fftshift(fft(x, N));
    plot_signal(abs(fx), "|X(f)|", "Frequency (Hz)", "Spectrum of the x(n) signal, N = " + N, true, N, p);
end