50 lines
1 KiB
Mathematica
50 lines
1 KiB
Mathematica
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clear;
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close all;
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Fe = 24000;
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Te = 1/Fe;
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Rb = 6000;
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M = 2^2;
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Ts = log2(M)/Rb;
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Ns = floor(Ts/Te);
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N = 20;
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bits = randi([0, 1], 1, N);
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T = (0:N*Ns/log2(M)-1) * Te;
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X_r = reshape(bits, 2, N/2).'; % on regroupe pour avoir un symbole 4-aire
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X_d = bi2de(X_r); % conversion en décimaux
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X_m = X_d*2 - 3; % mapping
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h = ones(1, Ns); % réponse impulsionnelle rectangulaire
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X_k = kron(X_m.', [1 zeros(1, Ns-1)]); % Suréchantillonnage
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X_f = filter(h, 1, X_k); % produit de convolution (filtrage)
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figure;
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plot(T, X_f);
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title("Signal transmis via le modulateur 2");
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xlabel("Secondes (s)");
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ylabel("Amplitude");
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ylim([ -3.1 3.1 ]);
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F = linspace(0, Fe/2, N);
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DSP_theorique = sinc(Ts*F).^2;
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DSP_numerique = pwelch(X_f);
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F_num = linspace(0, Fe/2, length(DSP_numerique));
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figure;
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plot(F_num, DSP_numerique/max(smoothdata(DSP_numerique)));
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hold;
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plot(F, DSP_theorique);
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title("DSP du signal transmis via le modulateur 2 et son équivalent théorique");
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xlabel("Fréquence (Hz)");
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ylabel("Amplitude");
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ylim([ 0 2 ]);
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legend("DSP numérique", "DSP théorique");
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